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Before the American Association for the Advancement 
of Science, Baltimore, Friday, January 1, 1909 




Copyright, 1909, 


Published April, 1909 





T. C. Chamberlin, University of Chicago 


Edward B. Poulton, Oxford University 



John M. Coulter, University of Chicago 


TION .72 

David Starr Jordan, Stanford University 



Edmund B. Wilson, Columbia University 


D. T. MacDougal, Carnegie Institution of Wash¬ 



W. E. Castle, Harvard University 


Chas. B. Davenport, Carnegie Institution of 


Carl H. Eigenmann, Indiana University 


Henry Fairfield Osborn, Columbia University 
and American Museum of Natural History 


G. Stanley Hall, Clark University 


Plate I.125 

Fig. 1. Leptinotarsa undecimlineata, normal form. 

Fig. 2. Form derived from L. undecimlineata through 
the application of the climatic conditions. 

Figs. 3, 4. Normal mitosis of nuclei in cells of plant. 

Figs. 5, 6, 7, 8. Irregularities of mitosis in cells of 
onion roots resulting from exposure to radium. 
[After Gager.] 

Plate II.133 

T. T. Upper and lower aspects of rosette of CEnothera 

D. D. Rosette of derivative resulting from ovarial 
treatment with zinc sulphate. 

Plate III. A Few of the Numerous Types of Teeth in 

the Characins .192 

Plate IV. Some Similarities in the Characins . . 192 

Plate V.245 

Rectigradations in the Teeth of Eocene Ungulates. 

Top View of Three Skulls of Eocene Titanotiieres 
Illustrating Brachycephaly, Mesaticephaly, and 
Dolichocephaly Respectively. 




The greatness of a man is shown in what he 
is, in what he does, and in what he sets a-doing. 

If the long list of contributions to the sessions 
of this Association have been, for these fifty 
were searched for products of thought whose 
stimulus sprang from the life and works of 
Charles Darwin, it would reveal an impressive 
testimonial to his greatness as a power in our 
scientific world. If it were possible to give such 
an intellectual product a material embodiment 
and an appropriate form, we could raise no more 
sincere monument to his memory. Even in the 
less tangible form it inevitably bears, it is our 
monument. By responses, individual and col¬ 
lective, to the marvelous suggestiveness of Dar¬ 
win’s inquiries and interpretations, the members 
of this Association during the last half century 
years, paying their truest tributes. More or less 
unconsciously, no doubt, but none the less gen¬ 
uinely, we have thus been doing honor to one of 
the greatest of intellectual leaders. 

The magnitude of any moving force is meas¬ 
ured scarcely less by the obstacles surmounted 



and by the inertia overcome than by the positive 
momentum it generates. In the first decades of 
the great Darwinian movement in biology, the 
tribute of our members may not have been want¬ 
ing in demonstrations of the force of old adhe¬ 
sions, but even then, whether by resistance or by 
cooperation, we gave our testimony to the new 
power that made itself felt in the scientific world. 
A little later we paid the tribute of conviction— 
the general tribute of willing conviction, on the 
part of some of us, and the even more significant 
tribute of reluctant conviction, on the part of 
others; but, in one way or another, we paid a uni¬ 
versal tribute. 

If we of the older school permit ourselves to be 
reminiscent, the tides of thought and feeling of 
the early days of the half century we celebrate 
easily surge back into consciousness. We readily 
recall the stirrings in the biological field when the 
great question of derivation of species arose into 
a concrete and, as it seemed to some, a threaten¬ 
ing form. But it was not among us as biolo¬ 
gists, but among us as members of a proud race, 
that emotion was deepest stirred. It was in the 
humanistic atmosphere that protests were most 
vibrant, for man—scientific man not excepted— 
is first of all a creature who takes thought of him¬ 
self. His anthropic pride, fostered by tradi¬ 
tional assumptions of separateness and eminent 
superiority—assumptions peculiar to no race, 
nation, or religion, but the common inheritance 




of us all—rose up in remonstrance and put bar¬ 
riers in the way of a candid reception of the new 
interpretations. But still, with all his foibles, 
man, at least man of the better sort, proclaims 
adhesion to the ancient admonition, “ Know thy¬ 
self,” and ultimately he strives to be loyal to the 
intellectual precedence he assigns himself. It is 
his to know the truth. Those of scientific trend 
early found occasion to call into fresh activity 
the maxim that it is better to accept the truth 
than to think of ourselves more highly than we 
ought to think. Whatever rufflings of our fond 
sense of humanistic caste were felt from the new 
interpretations in those first days of disturbed 
equanimity, we soon came to find complacency 
in the new place assigned us at the head of a 
multitudinous kin, the place of leadership in the 
van of a great procession of ascending tribes 
striving for supreme fitness. 

But the days of disturbed tranquillity, for us 
of the scientific household at least, soon passed 
away; and, if they linger with any still, it can only 
be among those outside the wide limits of this 
Association. We are yet far from knowing the 
whole truth, but we are tranquil in the search for 
it, welcome or unwelcome as it may prove at first 
to be. 

In the later decades of this memorable half 
century, the tribute of our membership, indi¬ 
vidual and collective, has lain in attempts to 
extend, to amend, to qualify, and to apply the 



parent thought to which Darwin gave such pro¬ 
digious impetus. To what result we have labored 
to add to, or to subtract from, his great concep¬ 
tion, the future must decide. The effort is our 
tribute to the power that has moved us. 

The biological realm was indeed the center of 
the great movement. Of this central movement 
and of the varied lines into which it has deployed, 
we shall learn through the words of those who are 
entitled to speak. To these, in a moment, I 
shall give place. But, though the revolution had 
its origin in the biological field, it was by no 
means limited to it. It soon became a radiant 
influence so penetrating and so stimulating that 
it has been felt in every field of thought. No 
realm of the intellectual world has failed to re¬ 
spond to the power of Darwin’s method, the can¬ 
dor of his spirit, and the force of his clear insight 
and restrained judgment. 

Darwin not only gave form to the whole trend 
of evolutionary inquiry, but he chastened and re¬ 
fined the moral aspects of thought in all lines of 
serious intellectual endeavor. It would be too 
much to say that he was the father of the evolu¬ 
tionary conception or the sole parent of the 
chastened moral attitude of thought now felt to 
be binding in the scientific world. We would do 
him a dishonor most obnoxious to his candid and 
truthful spirit if we were to assign him more than 
historic truth amply warrants. We must not 
fail to recognize that before his time the evolu- 



tionary conception had found place in the thought 
of not a few philosophic inquirers, not the least 
among whom was one of his own lineage; but yet 
it was Charles Darwin, more than any other, who 
gave definiteness and concreteness, who gave 
method and spirit, to the doctrine of derivation, 
and who thus became parental to the great move¬ 
ment in a sense equaled by no other. Such ac¬ 
ceptances of evolutionary conceptions as had much 
currency before his day, or had much tangible 
influence on research, were cosmogonic rather 
than biologic. Beyond doubt these pioneer 
gropings in the less biased fields prepared the 
way for his great contribution, but they did not 
equally encounter the central obstacle that lay in 
inherited adhesions and traditional preposses¬ 
sions, and they did not, therefore, and could not, 
equally revolutionize the spirit and the attitude 
of the thinking world by touching with trans¬ 
forming power the mainspring of bias. 

But if Darwin found some measure of prep¬ 
aration for his work in the labors of predecessors 
in his own and other fields, he more than amply 
repaid the debt. The stimulative influence of 
Darwinism on fundamental conceptions in the 
celestial and terrestrial kingdoms followed close 
on those in the biological realm. Both terrestrial 
and celestial history are even now in the flux of 
reinterpretation. The sources of this revision of 
view are indeed various, but a profound Dar¬ 
winian influence is felt in it all. It "would have 



been felt had Darwin left nothing but his 
Origin of Species and the remarkable trea¬ 
tises that followed it, but he has added thereto 
leaders of thought of his own name and lineage, 
and they have carried his spirit and his breadth 
of view into realms he could not himself enter. 
The evolution of the earth and of the heavens 
has thus felt his transmitted touch. The 
concept of kinship of worlds follows eas¬ 
ily on the concept of the kinship of organic 

In the transformed attitude of the intellectual 
world to-day, the mooted question of the hour— 
the evolution of the atom—finds a fair field, 
wherein evidence needs but to accredit itself duly 
to have its place and weight freely accorded it. 
If the atom shall show an authenticated pedigree, 
it will easily take its place in the procession of 
the derived, with the plant, the animal, the earth, 
and the stars. 

The contributions of Darwin to the science 
which it has fallen to me to follow have been great 
and various, but the greatest of them all relate 
to the history of life on the globe. The geolog¬ 
ical record, as known in his day, was at once a 
foundation for his work and an obstacle to its 
acceptance. It was the mission of his interpre¬ 
tations to bring forth the added truth which made 
the foundation broader and firmer, and which not 
only removed the seeming obstacles in the evolu¬ 
tionary path, but replaced them by cogent evi- 



dence of the continuity of life and of its successive 
steps of progress. 

But it does not fall to me to enter upon any of 
the special fields to which Darwin made his mon¬ 
umental contributions. Your committee has 
wisely assigned the leading aspects of the theory 
of evolution to those peculiarly fitted to treat 
them by reason of their own high attainments. 
In this introductory word on behalf of the Asso¬ 
ciation, I have found no more fitting way to ex¬ 
press our appreciation than to recall the tribute 
we have been paying by what we have done, and 
what we are trying to do, because Darwin set us 




On this historic occasion it is of special interest 
to reflect for a few moments on the part played 
by the New World in the origin and growth of 
the great intellectual force which dominates the 
past half century. The central doctrine of evo¬ 
lution, quite apart from any explanation of it, 
was first forced upon Darwin’s mind by his South 
American observations during the voyage of the 
Beagle; and we may be sure that his experience 
in this same country, teeming with innumerable 
and varied forms of life, confirmed and deepened 
his convictions as to the importance of adaptation 
and thus prepared the way for Natural Selection. 
Wallace, too, at first traveled in South America; 
only later in the parts of the Old World tropics 
which stand next to South America in richness. 

Asa Gray in the New World represented Sir 
Joseph Hooker in the Old, as regards the help 
given to Darwin before the appearance of the 
Origin, and in strenuous and most efficient de¬ 
fense after its appearance. Chauncey Wright 
similarly represents Henry Fawcett. Fritz 
Muller not only actively defended Darwin, but 




continually assisted him by the most admirable 
and original observations carried out at his Bra¬ 
zilian home. Turning to those who in some im¬ 
portant respects differed from Darwin, I do not 
think a finer example of chivalrous controversy 
can be found than that carried on between him 
and Hyatt. The immense growth of evolution¬ 
ary teaching, in which John Fiske played so im¬ 
portant a part, although associated with the name 
of Herbert Spencer, must not be neglected on 
an occasion devoted to the memory of Darwin. 

Outside the conflict which raged around the 
Origin, we find Dana, the only naturalist who at 
first supported Darwin in his views on the per¬ 
sistence of ocean basins and continental areas, and 
Alexander Agassiz, for many years the principal 
defender of the Darwinian theory of coral islands 
and atolls. 

American paleontology, famed throughout the 
world, has exercised a profound influence on the 
growth and direction of evolutionary thought. 
The scale and perfection of its splendid fossil 
records have attracted the services of a large band 
of the most eminent and successful laborers, of 
whom I can only mention the leaders:—Leidy, 
Cope, Marsh, Osborn, and Scott in the Ver- 
tebrata; Hall, Hyatt, and Walcott in the Inver¬ 
tebrate sub-kingdom. The study of American 
paleontology was at first believed to support a 
Neo-Lamarckian view of evolution, but this, as 
well as the hypothesis of polyphyletic origins, 



was undermined by the teachings of Weismann. 
Difficulties for which the Lamarckian theory had 
been invoked were met by the hypothesis of 
Organic Selection suggested by Baldwin and 
Osborn, and in England by Lloyd Morgan. 
Weismann’s contention that inherent characters 
are alone transmissible by heredity has also re¬ 
ceived strong support from the immense body of 
cytological, Mendelian, and mutationist work to 
which the present volume bears such eloquent tes¬ 
timony. Finally, the flourishing school of Amer¬ 
ican psychology, under the leadership of William 
James and James Mark Baldwin, accepts, and in 
accepting helps to confirm, the theory of Natural 


Professor Henry F. Osborn, in his interest¬ 
ing work From the Greeks to Darwin , con¬ 
cludes that Lamarck was unaware of Erasmus 
Darwin’s Zoonomia, and that the parallelism of 
thought is a coincidence. 1 The following passage 
from a letter 2 written to Huxley probably in 
1859, and published since the appearance of Pro¬ 
fessor Osborn’s book, indicates that Charles Dar¬ 
win suspected the French naturalist of borrowing 
from his grandfather:— 

1 From the Greeks to Darwin, New York, 1894, pp. 152-55. Pro¬ 
fessor Osborn shows that on p. 145 Erasmus Darwin made use of 
the term “acquired” in the sense of “acquired characters”; 
“ changement acquis ” is the form employed by Lamarck. 

2 More Letters of Charles Darwin, I, p. 125. 



“ The history of error is quite unimportant, but it is 
curious to observe how exactly and accurately my 
grandfather (in Zoonomia , Vol. I, p. 504, 1794) gives 
Lamarck’s theory. I will quote one sentence. Speaking 
of birds’ beaks, he says: 4 All which seem to have been 
gradually produced during many generations by the 
perpetual endeavor of the creatures to supply the want 
of food, and to have been delivered to their posterity 
with constant improvement of them for the purposes 
required.’ Lamarck published Hist. Zoolog. in 1809. 
The Zoonomia was translated into many languages.” 

A careful comparison of the French transla¬ 
tion of the Zoonomia with Lamarck’s Philosophic 
Zoologique and with a preliminary statement of 
his views published in 1802, would probably de¬ 
cide this interesting question. 



The limits of space compel me to pass by the 
youth of Charles Darwin, with the influence of 
school, Edinburgh and Cambridge, including the 
intimacy with Henslow and Sedgwick—friend¬ 
ships leading to his voyage in the Beagle , an 
event which more than any other determined his 
whole career. We must also pass by his earliest 
convictions on evolution, the first note-book begun 
in 1837, the reading of Malthus and discovery of 
Natural Selection in October, 1838, the imper¬ 
fect sketch of 1842, the completed sketch of 1844. 

It is necessary, however, to pause for a brief 
consideration of the influence of Sir Charles 



Lyell. Although the writings of the illustrious 
geologist have always been looked upon as among 
the greatest of the forces brought to bear upon 
the mind of Darwin, evidence derived from the 
later volumes of correspondence justifies the be¬ 
lief that the effect was even greater and more sig¬ 
nificant than has been supposed. 

Huxley has maintained with great force that 
the way was paved for Darwin by Lyell’s Prin¬ 
ciples of Geology far more thoroughly than by 
any other work. 

“ . . . Consistent uniformitarianism postulates evo¬ 
lution as much in the organic as in the inorganic 
world. The origin of a new species by other than ordi¬ 
nary agencies would be a vastly greater ‘ catastrophe ’ 
than any of those which Lyell successfully eliminated 
from sober geological speculation.” 1 

When the Principles first appeared Darwin 
was advised by Henslow to obtain and study the 
first volume, “ but on no account to accept the 
views therein advocated.” But a study of the 
very first place at which the Beagle touched, St. 
Iago, one of the Cape de Verde Islands, showed 
Darwin the infinite superiority of LyelFs teach¬ 
ings. He wrote to L. Horner, 2 August 29, 

“ I have been lately reading with care A. d’Orbigny’s 
work on South America, and I cannot say how forcibly 
impressed I am with the infinite superiority of the 
Lyellian school of Geology over the continental. I 

1 Life and Letters of Charles Darwin, II, p. 190. 

2 More Letters, II, p. 117. 



always feel as if my books came half out of Lyell’s brain, 
and that I never acknowledge this sufficiently; nor do I 
know how I can without saying so in so many words— 
for I have always thought that the great merit of the 
Principles was that it altered the whole tone of one’s 
mind, and therefore that, when seeing a thing never 
seen by Lyell, one yet saw it partially through his eyes 
—it would have been in some respects better if I had 
done this less, ...” 

This letter was written a few weeks after the 
date, July 5, 1844, which marks the completion 
of the finished sketch of that year. On July 5 
Darwin wrote the letter to his wife begging her, 
in the event of his death, to arrange for the pub¬ 
lication of the account he had just prepared. At 
this psychological moment in his career he wrote 
of the influence received from Lyell, and we are 
naturally led to observe how essentially Lyellian 
are the three lines of argument—two based on 
geographical distribution, one on the relation be¬ 
tween the living and the dead—which first led 
Darwin toward a belief in evolution! The 
thought which shook the world arose in a mind 
whose whole tone had been altered by Lyell’s 
teachings. Inasmuch as the founder of modern 
geology received his first inspiration from Buck- 
land, Oxford may claim some share in moulding 
the mind of Darwin. 



The characteristic feature in which Natural 
Selection differs from every other attempt to 



solve the problem of evolution is the account 
taken of the struggle for existence, and the role 
assigned to it. This struggle is keenly appre¬ 
ciated in Tennyson’s noble poem, In Memoriam, 
the dedication of which is dated 1849, ten years 
before the Origin. The poet is disquieted by:— 

and by 

44 Nature red in tooth and claw 
With ravine, ...” 

, . . finding that of fifty seeds 

She often brings but one to grow.” 

It is interesting to note that the obvious under¬ 
statement of this last passage is corrected in the 
author’s notes published by his son a few years 
ago. In these we find for “ fifty ” read 
“ myriad.” The poignant sense of the waste of 
individual lives is brought into close relation in 
the poem with the destruction of the type or 

44 So careful of the type she seems, 

So careless of the single life; 

• • • ^ • • 

4 So careful of the type ’? but no, 

From scarped cliff and quarried stone 
She cries 4 A thousand types are gone: 

I care for nothing, all shall go.’ ” 

In this association between the struggle for 
existence waged by individuals and the extinction 
and succession of species we seem to approach 
the central idea of Darwin and Wallace. I asked 
Dr. Grove of Newport in the Isle of Wight if he 



would point out the parallelism, so far as it ex¬ 
isted, to his illustrious patient, hoping that some 
light might be thrown on the source of the in¬ 
spiration. Nor was I disappointed. “ Stay,” 
said the aged poet when Dr. Grove had spoken, 
In Memoriam was published long before the 
Origin of Species .” 44 Oh! Then you are the 
man,” replied the doctor. 44 Yes, I am the man.” 
There was silence for a time and then Tennyson 
said : 44 I don’t want you to go away with a wrong 
impression. The fact is that long before Dar¬ 
win’s work appeared these ideas were known and 
talked about.” From this deeply interesting 
conversation I think it is probable that, through 
mutual friends, some echo of Darwin’s researches 
and thoughts had reached the great author of 
In Memoriam. 

The light which has been recently thrown 1 upon 
Philip Gosse’s remarkable book, Omphalos , indi¬ 
cates that its appearance in 1858 was connected 
with the thoughts that were to arouse the world 
in the following year. The author of Omphalos 
was a keen and enthusiastic naturalist held fast 
in the grip of the narrowest of religious creeds. 
We learn with great interest that he and others 
were by Lyell’s advice prepared beforehand for 
the central thoughts of the Origin. To the new 
teaching all the naturalist side of his nature re¬ 
sponded, but from it the religious side recoiled. 
Religion conquered in the strife, but the natural- 

1 In Father and Son, London, 1907. 



ist found comfort in the perfectly logical con¬ 
clusion that:— 

“ Any breach in the circular course of nature could 
be conceived only on the supposition that the object 
created bore false witness to past processes, which had 
never taken place.” 1 

Thus the divergence between the literal inter¬ 
pretation of Scripture and the conclusions of 
both geologist and evolutionist were for this re¬ 
markable man reconciled by the conviction:— 

44 That there had been no gradual modification of the 
surface of the earth, or slow development of organic 
forms, but that when the catastrophic act of creation 
took place, the world presented, instantly, the structural 
appearance of a planet on which life had long existed.” 2 

Philip Gosse could not but believe that the 
thoughts which had brought so much comfort to 
himself would prove a blessing to others also. 
He offered Omphalos “ with a glowing gesture, 
to atheists and Christians alike. . . . But, 
alas! atheists and Christians alike looked at it 
and laughed, and threw it away .” 3 Charles 
Kingsley expressed the objection felt by the 
Christian when he wrote that he could not “ be¬ 
lieve that God had written on the rock one enor¬ 
mous and superfluous lie.” 4 

About twenty years ago I was present when 
precisely the same conclusion was advanced by a 
high dignitary of the English Church. He 
argued that even if the history of the Universe 

1 Father and Son , pp. 120, 121. 2 L. c ., p. 120. 

3 L. c., p. 122. 4 Ibid. 



were carried back to a single element such as 
hydrogen, the human mind would remain unsat¬ 
isfied and would inquire whence the hydrogen 
came, and that any and every underlying form 
of matter must leave the inexorable question 
“whence?” still unanswered. Therefore if in 
the end the question must be given up, we may 
as well, he argued, admit the mystery of creation 
in the later stages as in the earlier. Thus he 
arrived at the belief in a world formed instanta¬ 
neously, ready-made and complete, with its fos¬ 
sils, marks of denudation, and evidences of evolu¬ 
tion—a going concern. Aubrey Moore, the 
clergyman who more than any other man was 
responsible for breaking down the antagonism 
toward evolution then widely felt in the English 
Church, replied very much as Kingsley had done, 
that he was unwilling to believe that the Creator 
had deliberately cheated the intellectual powers 
He had made. I may add that, inasmuch as 
science consists in the attempt to carry down 
causation as far as possible, it is above all the 
scientific side of the human intellect that is out¬ 
raged,—no weaker term can be used,—by this 
more modern development of the argument of 


In May, 1856, Darwin, urged by Lyell, began 
to prepare for publication. He had determined 



to present his conclusions in a volume, for he was 
unwilling to place any responsibility for his 
opinions on the council of a scientific society. On 
this point he was, as he told Sir Joseph Hooker, 
in the only fit state for asking advice; namely, 
with his mind firmly made up: then good advice 
was very comforting while it was perfectly easy 
to reject bad advice. The work was continued 
steadily until June 18, 1858, when Wallace’s let¬ 
ter and essay arrived from Ternate. As a result 
of the anniversary held in London on July 1 last 
year new light has been thrown upon the circum¬ 
stances under which the joint essay was published 
fifty years before. 

In consequence of the death of the eminent 
botanist, Robert Brown, Vice-President and ex- 
President of the Linnean Society, the last meet¬ 
ing of the summer session, called for June 17, 
was adjourned. The by-laws required that the 
vacancy on the Council should be filled up within 
three months, and a special meeting was called 
for July 1, for this purpose. Darwin received 
Wallace’s essay on June 18, too late for the sum¬ 
mer meetings of the Society, but in good time for 
Lyell and Hooker to present it to the special 
meeting. Hence, as Sir Joseph Hooker said on 
July 1st last, the death of Robert Brown caused 
the theory of Natural Selection to be “ given to 
the world at least four months earlier than would 
otherwise have been the case.” Sir Joseph 
Hooker also informed us that from June 18 up 



to the evening of July 1, when he met Sir Charles 
Lyell at the Society, all the intercourse with 
Darwin and with each other was conducted by 
letter, and that no fourth person was admitted 
into their confidence. The joint essay was read 
by the secretary of the Society. Darwin was 
not present, but both Lyell and Hooker “ said 
a few words to emphasize the importance of the 
subject.” Among those who were present were 
Oliver, Fitton, Carpenter, Henfrey, Burchell, 
and Bentham, who was elected on the Council 
and nominated as Vice-President in place of 
Robert Brown. I cannot resist the temptation 
to reprint from the memorial volume issued by 
the Linnean Society of London some passages 
in the address which A. R. Wallace felt con¬ 
strained to deliver on July 1, 1908, protesting 
against the too great credit which he believed had 
been assigned to himself. After describing Dar¬ 
win’s discovery of Natural Selection and the 
twenty years devoted to confirmation and patient 
research, Wallace continued:— 

“ How different from this long study and preparation 
—this philosophic caution—this determination not to 
make known his fruitful conception till he could back it 
up by overwhelming proofs—was my own conduct. The 
idea came to me, as it had come to Darwin, in a sudden 
flash of insight: it was thought out in a few hours— 
was written down with such a sketch of its various appli¬ 
cations and developments as occurred to me at the 
moment,—then copied on thin letter-paper and sent off 
to Darwin—all within one week. I was then (as often 
since) the 6 young man in a hurry 9 ; he, the painstaking 



and patient student, seeking ever the full demonstration 
of the truth he had discovered, rather than to achieve 
immediate personal fame. 

“ Such being the actual facts of the case, I should 
have had no cause for complaint if the respective shares 
of Darwin and myself in regard to the elucidation of 
nature’s method of organic development, had been 
thenceforth estimated as being, roughly, proportional to 
the time we had each bestowed upon it when it was 
thus first given to the world—that is to say, as twenty 
years is to one week. For, he had already made it his 
own. If the persuasion of his friends had prevailed with 
him, and he had published his theory after ten years’, 
fifteen years’, or even eighteen years’ elaboration of it, 
I should have had no part in it whatever, and he would 
have been at once recognized, and should be ever recog¬ 
nized, as the sole and undisputed discoverer and patient 
investigator of the great law of 4 Natural Selection ’ 
in all its far-reaching consequences. 

“ It was really a singular piece of good luck that 
gave me any share whatever in the discovery ... it 
was only Darwin’s extreme desire to perfect his work 
that allowed me to come in, as a very bad second, in the 
truly Olympian race in which all philosophical biologists, 
from Buff on and Erasmus Darwin to Richard Owen and 
Robert Chambers were more or less actively engaged.” 


It is impossible to do more than refer briefly 
to the storm of opposition with which the Origin 
was at first received. The reviewer in the Athe- 
nccum for November 19, 1859, left the author 
“ to the mercies of the Divinity Hall, the Col¬ 
lege, the Lecture Room, and the Museum.” 1 
Dr. Whewell for some years refused to allow a 

1 Life and Letters, II, p. 228 n. 



copy of the Origin to be placed in the library of 
Trinity College, Cambridge. 1 My predecessor, 
Professor J. O. Westwood, proposed to the last 
Oxford University Commission the permanent 
endowment of a Reader to combat the errors of 
Darwinism. “ Lyell had difficulty in preventing 
[Sir William] Dawson reviewing the Origin on 
hearsay, without having looked at it. No spirit 
of fairness can be expected from so biased a 
judge.” 2 And even when naturalists began to 
be shaken by the force of Darwin’s reasoning, 
they were often afraid to own it. Thus Darwin 
wrote to H. Fawcett, on September 18, 1861:— 

“ Many are so fearful of speaking out. A German 
naturalist came here the other day; and he tells me that 
there are many in Germany on our side, but that all 
seem fearful of speaking out, and waiting for some one 
to speak, and then many will follow. The naturalists 
seem as timid as young ladies should be, about their 
scientific reputation.” 3 

Among the commonest criticisms in the early 
days, and one that Darwin felt acutely, 4 was the 
assertion that he had deserted the true method of 
scientific investigation. One of the best exam¬ 
ples of these is to be found in the letter, Decem¬ 
ber 24, 1859, of Darwin’s old teacher in geology, 
Adam Sedgwick:— 

1 Life and Letters , II, p. 261. 

2 From a letter written by Darwin, November 4, 1862. More 
Letters, I, p. 468. 

3 More Letters , I, p. 196. 

4 See Darwin’s letter to Henslow, May 8, 1860. More Letters , 
I, pp. 149, 150. 



“ You have deserted —after a start in that tram-road 
of all solid physical truth—the true method of induc¬ 
tion, and started us in machinery as wild, I think, as 
Bishop Wilkins’s locomotive that was to sail with us to 
the moon.” 1 

These wild criticisms were soon set to rest by 
Henry Fawcett’s article in Macmillan s Maga¬ 
zine in 1860 and by a paper read before the 
British Association by the same author in 1861. 
Referring to this defense, Fawcett wrote to Dar¬ 
win, July 16, 1861:— 

“ I was particularly anxious to point out that the 
method of investigation was in every respect philosoph¬ 
ically correct. I was spending an evening last week 
with our friend Mr. John Stuart Mill, and I am sure 
you will be pleased to hear that he considers your reason¬ 
ing throughout is in the most exact accordance with 
the strict principles of logic. He also says the method 
on investigation you have followed is the only proper 
one to such a subject. It is easy for an antagonistic 
reviewer, when he finds it difficult to answer your argu¬ 
ments, to attempt to dispose of the whole matter by 
uttering some such commonplace as 4 This is not a 
Baconian induction.’ ” 

• •••••• 

“ As far as I am personally concerned, I am sure I 
ought to be grateful to you, for since my accident 
nothing has given me so much pleasure as the perusal of 
your book. Such studies are now a great resource 
to me.” 2 

1 Life and Letters , II, p. 248. See also the Quarterly Review 
for July, 1860. Sedgwick’s review in the Spectator, March 24, 
1860, contains the following passage: “ . . . I cannot conclude 
without expressing my detestation of the theory, because of its 
unflinching materialism; because it has deserted the inductive 
track, the only track that leads to physical truth; because it 
utterly repudiates final causes, and thereby indicates a demoralized 
understanding on the part of its advocates.” Quoted in Life and 
Letters, II, p. 298. 

2 More Letters, I, pp. 189, 190. 



To this Darwin replied:— 

“ You could not possibly have told me anything 
which would have given me more satisfaction than what 
you say about Mr. Mill’s opinion. Until your review 
appeared I began to think that perhaps I did not under¬ 
stand at all how to reason scientifically.” 1 


It is remarkable to contrast the maturity, the 
balance, the judgment, with which Darwin put 
forward his views, with the rash and haphazard 
objections and rival suggestions advanced by his 
critics. It is doubtful whether so striking a con¬ 
trast is to be found in the history of science;— 
on the one side twenty years of thought and in¬ 
vestigation pursued by the greatest of naturalists, 
on the other offhand impressions upon a most 
complex problem hastily studied and usually very 
imperfectly understood. It is not to be won¬ 
dered at that Darwin found the early criticisms 
so entirely worthless. The following extract 
from an interesting letter 2 to John Scott, written 
on December 3, 1862, shows how well aware he 
was of difficulties unnoticed by critics:— 

“You speak of difficulties on Natural Selection: 
there are indeed plenty; if ever you have spare time 
(which is not likely, as I am sure you must be a hard 
worker) I should be very glad to hear difficulties from 
one who has observed so much as you have. The major- 

1 More Letters, I, p. 189. 2 More Letters, II, p. 311. 



itj of criticisms on the Origin are, in my opinion, not 
worth the paper they are printed on.” 

From the very first the most extraordinarily 
crude and ill-considered suggestions were put for¬ 
ward by those who were unable to recognize the 
value of the theory of Natural Selection. A 
good example is to be found in Andrew Mur¬ 
ray’s principle of a sexual selection based on con¬ 
trast,—“ the effort of nature to preserve the typ¬ 
ical medium of the race.” 1 And even in these 
later years the wildest imaginings may be put 
forward in all seriousness as the interpretation of 
the world of living organisms. Thus in Beccari’s 
interesting work on Borneo, 2 the author com¬ 
pares the infancy and growth of the organic world 
with the development and education of an indi¬ 
vidual. In youth the individual learns easily, 
being unimpeded by the force of habits, while 
“ with age heredity acts more strongly, instincts 
prevail, and adaptation to new conditions of ex¬ 
istence and to new ideas becomes more difficult; 
in a word, it is much less easy to combat hered¬ 
itary tendencies.” Similarly in the state of ma¬ 
turity now reached by the organic world Beccari 
believes that the power of adaptation is well-nigh 
non-existent. Heredity, through long accumula¬ 
tion in the course of endless generations, has be¬ 
come so powerful that species are now stereo¬ 
typed and cannot undergo advantageous changes. 

1 Life and Letters, II, p. 261. 

2 Wanderings in the Great Forests of Borneo, London, 1904. 
English translation, pp. 209-16. 



For the same reason acquired characters cannot 
now be transmitted to offspring. Beccari imag¬ 
ines that everything was different in early ages 
when, as he supposes, life was young and heredity 
weak. In this assumed “ Plasmatic Epoch ” the 
environment acted strongly upon organisms, 
evoking the responsive changes which have now 
been rendered fixed and immovable by heredity. 

Even the hypothesis proposed as a substitute 
for Natural Selection by so distinguished a bot¬ 
anist as Carl Nageli turns out to be most unsat¬ 
isfactory the moment it is examined. The idea 
of evolution under the compulsion of an internal 
force residing in the idioplasm is in essence but 
little removed from special creation. On the sub¬ 
ject of Nageli’s criticisms Darwin wrote, 1 Au¬ 
gust 10, 1869, to Lord Farrer:— 

“ It is to me delightful to see what appears a mere 
morphological character found to be of use. It pleases 
me the more as Carl Nageli has lately been pitching into 
me on this head. Hooker, with whom I discussed the 
subject, maintained that uses would be found for lots 
more structures, and cheered me by throwing my own 
orchids into my teeth.” 



It is interesting to put side by side passages 
from two letters 2 written by Darwin to Hooker, 
one in 1845 at the beginning of their friendship, 

1 More Letters, II, p. 380. 

2 L. c., I, p. 39. The passages here quoted are put side by side 
by the editors of this work. 



the other thirty-six years later, a few months be¬ 
fore Darwin’s death. The first shows the instant 
growth of their friendship: “Farewell! What 
a good thing is community of tastes! I feel as if 
I had known you for fifty years. Adios.” 

The second letter expresses at the end of Dar¬ 
win’s life the same feelings which find utterance 
ever and again throughout the long years of his 

“ Your letter has cheered me, and the world does not 
look a quarter so black this morning as it did w T hen 
I wrote before. Your friendly words are worth their 
weight in gold.” 

The friendship with Asa Gray began with a 
meeting at Kew some years before the publica¬ 
tion of Natural Selection. Darwin soon began 
to ask for help in the work, which was ultimately 
to appear as the Origin. The following letter to 
Hooker, June 10, 1855, shows what he thought 
of the great American botanist:— 

“ I have written him a very long letter, telling him 
some of the points about which I should feel curious. 
But on my life it is sublimely ridiculous, my making 
suggestions to such a man.” 1 

The friendship ripened very quickly, so that on 
July 20, 1856, Darwin gave Asa Gray an account 
of his views on evolution, 2 and on September 5 
of the following year a tolerably full description 3 

1 More Letters , I, p. 418. Asa Gray’s generous reply is printed 
on p. 421. 

2 Life and Letters , II, p. 78. 

8 L. c., pp. 119, 120. 



of Natural Selection. From this latter letter 
Darwin chose the extracts which formed part of 
his section of the joint essay published July 1, 

Asa Gray’s opinion on first reading the Origin 
was expressed not to Darwin but to Hooker in 
a letter written January 5, 1860:— 

“ It is done in a masterly manner. It might well 
have taken twenty years to produce it. It is crammed 
full of most interesting matter—thoroughly digested— 
well expressed—close, cogent, and taken as a system it 
makes out a better case than I had supposed pos¬ 
sible. ...” 

After attending to Agassiz’s unfavorable 
opinion of his book, he continues: “ Tell Darwin 
all this. I will write to him when I get a chance. 
As I have promised, he and you shall have fair 
play here. ...” 1 A little later, when on Jan¬ 
uary 23, he w T rote to Darwin himself, Asa Gray 
concluded: “ I am free to say that I never learnt 
so much from one book as I have from yours.” 2 

It is impossible to do justice on the present 
occasion to the numerous letters in which Darwin 
expressed his gratitude for the splendid manner 
in which Asa Gray kept his word and “ fought 
like a hero in defense.” 3 At a time when few 
naturalists were able to understand the drift of 
Darwin’s argument, the acute and penetrating 
mind of Asa Gray had in a moment mastered 
every detail. Thus Darwin wrote on July 22, 

1 Life and Letters, II, p. 268. 

2 L. c., p. 272. 

3 L. c., p. 310. 



1860, concerning the article in the Proceedings 
of the American Academy for April 10:— 

“ I can not resist expressing my sincere admiration 
of your most clear powers of reasoning. As Hooker 
lately said in a note to me, you are more than any 
one else the thorough master of the subject. I declare 
that you know my book as well as I do myself; 
and bring to the question new lines of illustration and 
argument in a manner which excites my astonishment 
and almost my envy! . . . Every single word seems 

weighed carefully, and tells like a 32-pound shot.” 1 

Some weeks later, on September 26, 1860, 
Darwin again expressed the same admiration, 
and stated that Asa Gray understood him more 
perfectly than any other friend:— 

“ . . . You never touch the subject without making 

it clearer. I look at it as even more extraordinary 
that you never say a word or use an epithet which does 
not express fully my meaning. Now Lyell, Hooker, 
and others, who perfectly understand my book, yet 
sometimes use expressions to which I demur.” 2 

Darwin also sent 3 Asa Gray’s defense of the 
Origin to Sir Charles Lyell, whom he was ex¬ 
tremely anxious to convince of the truth of evolu¬ 
tion. Asa Gray’s religious convictions pre¬ 
vented the full acceptance of Natural Selection. 
He was ever inclined to believe in the Providen¬ 
tial guidance of the stream of variation. He also 
differed from Darwin in the interpretation of 
all instincts as congenital habits. 4 

1 Life and Letters, II, p. 326. 2 L. c., pp. 344, 345. 

3 More Letters, I, p. 169. 

4 Life and Letters, III, p. 170. 



The same close intimacy and mutual help be¬ 
gun in the preparation of the Origin was con¬ 
tinued in Darwin’s later botanical works. Thus 
Darwin owed his Climbing Plants to the study 
of a paper by Asa Gray, and he dedicated 
his Forms of Flowers to the American botanist 
“as a small tribute of respect and affection.” 
Concerning some of the researches which after¬ 
ward appeared in this book, Darwin wrote: 1 “ I 
care more for your and Hooker’s opinion than 
that of all the rest of the world, and for Lyell’s 
on geological points.” 

Another great name, that of Huxley, is espe¬ 
cially associated in our minds with the defeat of 
those who would have denied that the subject was 
a proper one for scientific investigation. In the 
strenuous and memorable years that followed the 
appearance of the Origin the mighty warrior 
stands out as the man to whom more than to any 
other we owe the gift of free speech and free 
opinion in science,—the man so admirably de¬ 
scribed by Sir Ray Lankester at the Linnean 
celebration, “ the great and beloved teacher, the 
unequaled orator, the brilliant essayist, the un¬ 
conquerable champion and literary swordsman— 
Thomas Henry Huxley.” 

Comparing the friendships to which Darwin 
owed so much, Lyell was at first the teacher but 
finally the pupil,—unwilling and unconvinced at 
the outset, in the end convinced although still 

1 Life and Letters, III, p. 300. 



unwilling; Hooker in England and Asa Gray in 
America were the two intimate friends on whom 
he chiefly depended for help in writing the Origin 
and for supports to its arguments; Huxley was 
the great general in the field where religious con¬ 
victions, expressed or unexpressed, were the 
foundation of a fierce and bitter antagonism. 


An unnecessary bitterness was imported into 
the early controversies in England, because of 
the personality of the scientific leaders in the 
attacks on the Origin. Of these the chief was 
the great comparative anatomist, Richard Owen. 
In spite of his leading scientific position, this re¬ 
markable man withdrew from contact with his 
brother zoologists, living in a self-imposed isola¬ 
tion which tended towards envy and bitterness. 
The same unavailing detachment had been car¬ 
ried much further by the great naturalist W. J. 
Burchell, who, as from a watch-tower, looked 
upon the world he strove to avoid with an ab¬ 
sorbed and jealous interest. Professor J. M. 
Baldwin has shown how inevitable and inexorable 
is the grip of the social environment: the more 
we attempt to evade it the more firmly we seem 
to be held in its grasp. 

In the first years of the struggle Owen’s bitter 
antagonism made itself felt in the part he took 
as “ crammer ” to the Bishop of Oxford, and in 



his anonymous article in the Edinburgh Review 
for April, 1860. But Owen could not bear to 
remain apart from the stream of thought when 
there was no doubt about the way it was flowing, 
so that in a few years he was maintaining some 
of the chief conclusions of the Origin , although 
retracting nothing, but rather keeping up his bit¬ 
ter attacks upon Darwin. This treatment re¬ 
ceived from one who was all affability 1 when they 
met was naturally resented by Darwin, whose 
feelings on the subject are expressed in the fol¬ 
lowing passage from a letter to Asa Gray, 2 July 
28, 1862:— 

“ By the way, one of my chief enemies (the sole one 
who has annoyed me), namely Owen, I hear has been 
lecturing on birds; and admits that all have descended 
from one, and advances as his own idea that the oceanic 
wingless birds have lost their wings by gradual disuse. 
He never alludes to me, or only with bitter sneers, and 
coupled with Buff on and the Vestiges .” 

In the historical sketch added to the later edi¬ 
tions of the Origin , Owen is the only writer who 
is severely dealt with. In this introductory sec¬ 
tion Darwin said that he was unable to decide 
whether Owen did or did not claim to have orig¬ 
inated the theory of Natural Selection. 3 

About twelve years after the appearance of 
the Origin another opponent, St. George Mivart, 

1 “ Mrs. Carlyle said that Owen’s sweetness always reminded 
her of sugar of lead.” Life and Letters of T. H. Huxley, 
London, II, p. 167. 

2 More Letters , I, p. 203. 

3 Origin of Species, 6th ed., p. xviii. 



produced something of the same bitterness as 
Owen and for a similar reason. Thus Darwin 
wrote 1 to Hooker, September 16, 1871, as fol¬ 
lows :— 

“ You never read such strong letters Mivart wrote 
to me about respect towards me, begging that I would 
call on him, etc., etc.; yet in the Q. Review [July, 1871] 
he shows the greatest scorn and animosity towards 
me, and with uncommon cleverness says all that is most 
disagreeable. He makes me the most arrogant, odious 
beast that ever lived. I can not understand him; I 
suppose that accursed religious bigotry is at the root 
of it. Of course he is quite at liberty to scorn and 
hate me, but why take such trouble to express something 
more than friendship? It has mortified me a good 

On other occasions at a much later date I have 
myself observed that there was something pecu¬ 
liar about the poise of Mivart’s mind, which 
seemed ever inclined to pass with abrupt transi¬ 
tion from the extreme of an unnecessary effusive¬ 
ness to an unnecessarily extreme antagonism. 

Mivart’s attack, contained in his book The 
Genesis of Species , was effectively dealt with 
by Chauncey Wright in the North American 
Review for July, 1871. Darwin was so pleased 
with this defense that he obtained the author’s 
permission for an English reprint, 2 and with fur¬ 
ther additions it was published as a pamphlet by 

1 More Letters, I, p. 333. See also Life and Letters, III, 
p. 147. 

2 The pamphlet was published at Darwin’s expense. For his 
keenly appreciative letter to the author see Life and Letters, 

III, p. 145. 



John Murray in 1871. A copy presented by 
Darwin to the late J. Jenner Weir and now in 
the Library of the Hope Department of Oxford 
University Museum contains an interesting holo¬ 
graph letter referring to the pamphlet and bear¬ 
ing upon the controversy that followed upon the 
appearance of Mivart’s book. This letter is, by 
kind permission of the Darwin family, now made 

44 Down, 

44 Beckenham, Kent. 

64 Oct. 11, 1871. 

44 My dear Sir 

44 1 am much obliged for your kind note & invitation. 
I sh^ like exceedingly to accept it, but it is impossible. 
I have been for some months worse than usual, & can 
withstand no exertion or excitement of any kind, & in 
consequence have not been able to see anyone or go 
anywhere.—As long as I remain quite quiet, I can do 
some work, & I am now preparing a new and cheap 
Edit 11 of the Origin in which I shall answer Mr. 
Mivart’s chief objections. Huxley will bring out a 
splendid review on d° in the Contemporary R ., on 
November 1st. 

44 1 am pleased that you like Ch. Wright’s article. It 
seemed to me very clever for a man who is not a 
naturalist. He is highly esteemed in the U. States 
as a Mathematician & sound reasoner. 

44 I wish I could join your party.— 

44 My dear Sir 

44 Yours very sincerely 

44 Ch. Darwin.” 1 

Chauncey Wright speaks of presenting, in his 
review of Mivart, considerations “ in defense and 

1 The letter is addressed to J. Jenner Weir, Esq., 6 Haddo 
Villas, Blackheath, London, S. E. 



illustration of the theory of Natural Selection. 
My special purpose,” he continues, “ has been to 
contribute to the theory by placing it in its proper 
relations to philosophical inquiries in general.” 1 
This able critic in America and Henry Fawcett 
in England represent a class of thinkers who have 
taken and still take a very important part in up¬ 
holding the theory of Natural Selection. It is not 
necessary to be a biologist in order to compre¬ 
hend the details and the bearings of this theory. 
They were at the very first understood by able 
thinkers who were not scientific men or who fol¬ 
lowed some non-biological science, when natural¬ 
ists themselves were hopelessly puzzled. And at 
the present time such support is of the highest 
importance when within the limits of the sciences 
most nearly concerned the intense and natural 
desire to try all things is not always accompanied 
by the steadfast purpose to hold fast that which 
is good. 


The greatest change in evolutionary thought 
since the publication of the Origin was wrought, 
after Darwin’s death, by the appearance of that 
wonderful and beautiful theory of heredity, 
which looks on parents as the elder brother and 
sister of their children. In this theory, itself 
an outcome of minute and exact observation, 

1 Life and Letters , III, pp. 143, 144. 



Weismann raised the question of the hereditary 
transmission of acquired characters, the very 
foundation of Lamarckian evolution. Darwin 
accepted such transmission, and it was in order 
to account for “ the inherited effects of use and 
disuse, &c.,” 1 that he thought out his marvelous 
hypothesis of pangenesis. If such effects be not 
transmitted pangenesis becomes unnecessary and 
Weismann’s simpler, more convincing, and bet¬ 
ter supported hypothesis of the continuity of the 
germ-plasm takes its place. It is impossible on 
the present occasion to speak in any detail of the 
controversy which has raged intermittently dur¬ 
ing the past twenty years on this fascinating sub¬ 
ject. I will, however, briefly consider a single 
example of the error into which, as I believe, 
Darwin was led by following the Lamarckian 
theory of hereditary experience. I refer to the 
interpretation which he suggests for feelings of 
“ the sublime,” applying this term to the effect 
upon the brain of a vast cathedral, a tropical for¬ 
est, or a view from a mountain height. Thus, 
writing to E. Gurney, July 8, 1876, Darwin said 
on this subject:—“. . . possibly the sense of 
sublimity excited by a grand cathedral may have 
some connection with the vague feelings of terror 
and superstition in our savage ancestors, when 
they entered a great cavern or gloomy forest.” “ 
An interesting account is given by Romanes 3 

1 See the letter to Huxley, July 12 (1865?), in Life and Letters. 

2 Life and Letters, III, p. 186. 

3 Ibid., pp. 54, 55. See also I, pp. 64, 65. 



of Darwin’s own experiences of this feeling, re¬ 
lating how he at first thought that they were most 
excited by the magnificent prospects surveyed 
from the summits of the Cordilleras, but after¬ 
wards came down from his bed on purpose to 
correct this impression, saying that he felt most 
of the sublime in the forests of Brazil. 

We may first observe that the remarkable feel¬ 
ings induced by such experiences are very far 
from unpleasant, as we should expect them to be 
on the theory which refers them to the apprehen¬ 
sions and dangers of our primitive ancestors. 
Thus, on May 18 , 1832 , when the first impres¬ 
sions of a Brazilian forest were freshest in Dar¬ 
win’s mind, he wrote to Henslow, telling him of 
an expedition of 150 miles from Rio de Janeiro 
to the R. Macao. 

“ Here I first saw a tropical forest in all its sublime 
grandeur—nothing but the reality can give any idea 
how wonderful, how magnificent the scene is. . . . 

I never experienced such intense delight. I formerly 
admired Humboldt, I now almost adore him; he alone 
gives any notion of the feelings which are raised in 
my mind on first entering the tropics.” 1 

Furthermore, how are we to account on any 
such hypothesis for the similarity of the feelings 
excited by the forest, where enemies might lurk 
unseen, and the mountain peak, the very spot 
which offers the best facility for seeing them? It 
is also difficult to understand why the terrors of 
primitive man should be specially associated with 

1 Life and Letters , I, pp. 236, 237. 



caves or with the most magnificent forests on the 
face of the earth. There is no valid reason for 
believing that any less danger lurked amid trees 
of ordinary size or lay in wait for him by the 
riverside, in the jungle, or the rock-strewn waste. 
In the midst of life he was in death in every sol¬ 
itary place that could afford cover to an enemy; 
on the mountain top probably least of all. 

The feelings inspired by the interior of a cathe¬ 
dral are especially instructive in seeking the ex¬ 
planation of the psychological effect. We may 
be sure that the brain effect is here produced by 
the unaccustomed scale of the esthetic impression. 
A cathedral the size of an ordinary church would 
not produce it. However intensely we may ad¬ 
mire, the sense of the sublime is not excited or 
but feebly excited by the exterior of a cathedral, 
nor does it accompany the profound intellectual 
interest aroused by the sight of the pyramids. 
The thrill of the sublime, in the sense in which the 
term is here used, is, I do not doubt, the result of 
surprise and wonder raised to their highest power 
—a psychological shock at the reception of an 
esthetic visual experience on an unwonted scale, 
—vast as if belonging to a larger world in which 
the insignificance of man is forced upon him. It 
is not excited by the pyramids which are in form 
but symmetrical hills of stone, nor does the ex¬ 
terior of any building afford an experience suf¬ 
ficiently remote to produce the feeling in any high 



W. J. Burchell, in one of his letters 1 to Sir 
William Hooker, points out that the feelings of 
awe and wonder aroused in a Brazilian forest are 
not to be expected in those to whom the sight is 
familiar. As regards the depth and nature of 
the effects produced by the experiences here re¬ 
ferred to, it would be very interesting to com¬ 
pare the savage with the civilized man, the uned¬ 
ucated with the educated mind. That the results 
are intimately bound up with the psychological 
differences between individuals—in part inherent, 
in part due to training and experience—is well 
illustrated in a story told by the late Charles 
Dudley Warner, who took two English friends 
to see for the first time the Grand Canyon of 
the Colorado. When they reached the point 
where the whole prospect—boundless beyond im¬ 
agination—is revealed in a moment of time, one 
of his friends burst into tears, while the other 
relieved his feelings by unbridled blasphemy. 

The remarkable psychological effects of a 
grandeur far transcending and far removed from 
ordinary experience may be compared to the 
thrill 2 so often felt on hearing majestic music, a 
thrill we do not seek to explain as a faint, far-off 
reminiscence of dread inspired by the savage war- 
cry. I do not doubt that an explanation of the 
sublime based on the terrors of our primitive an- 

1 Preserved in the Library at Kew, but, I believe, as yet unpub¬ 

2 Darwin spoke of his backbone shivering during the anthem 
in King’s College chapel. Life and Letters , I, p. 49; see also 
p. 170. 



cestors is an example of the mistaken interpre¬ 
tations into which even Darwin was led by fol¬ 
lowing the hypothesis of Lamarck. 


One of the most recent attempts to defend the 
Lamarckian doctrine of the hereditary transmis¬ 
sion of acquired characters is contained in the 
important Presidential Address of Mr. Francis 
Darwin to the British Association at Dublin 
(1908). In this interesting memoir the author 
expresses his belief that such transmission is im¬ 
plied by the persistence of the successive develop¬ 
mental stages through which the individual 
advances toward maturity. Following Hering 
and Richard Semon he is disposed to explain the 
hereditary transmission of these stages by a 
process analogous to memory. It is interesting 
to observe that this very analogy had been 
brought before Charles Darwin, but failed to sat¬ 
isfy him. He wrote 1 to G. J. Romanes, May 29, 
1876 :— 

1 More Letters, I, p. 364. See also the following sentence in 
a letter on Pangenesis, written June 3, 1868, to Fritz Muller: “ It 
often appears to me almost certain that the characters of the 
parents are ‘photographed’ on the child, only by means of 
material atoms derived from each cell in both parents, and devel¬ 
oped in the child.” More Letters, II, p. 82. The following 
passage in a letter to Sir Joseph Hooker, February 28, 1868, is 
also of great interest: “When you or Huxley say that a single 
cell of a plant, or the stump of an amputated limb, has the 
‘ potentiality ’ of reproducing the whole or ‘ difluise an influence,’ 
these words give me no positive idea;—but when it is said that 
the cells of a plant, or stump, include atoms derived from every 
other cell of the whole organism and capable of development, I 
gain a distinct idea.” Life and Letters , III, p. 81. 



“ I send by this post an essay by Hackel attacking 
Pan. and substituting a molecular hypothesis. If I 
understand his views rightly, he would say that with 
a bird which strengthened its wings by use, the forma¬ 
tive protoplasm of the strengthened parts became 
changed, and its molecular vibrations consequently 
changed, and that these vibrations are transmitted 
throughout the whole frame of the bird, and affect 
the sexual elements in such a manner that the wings 
of the offspring are developed in a like strengthened 
manner. . . . He lays much stress on inheritance 

being a form of unconscious memory, but how far this 
is a part of his molecular vibration, I do not under¬ 
stand. His views make nothing clearer to me; but this 
may be my fault.” 

Should it hereafter be proved that acquired 
characters are transmitted, I can not but think 
that the interpretation will be on the lines of 
Charles Darwin’s hypothesis of Pangenesis. But 
the probability that any such result will be estab¬ 
lished, already shown to be extremely small, has 
become even more remote in the light of the re¬ 
cent investigations conducted by Mendelians and 

For the transmission of all inherent qualities, 
including the successive stages of individual de¬ 
velopment, Weismann’s hypothesis of the con¬ 
tinuity of the germ-plasm supplies a sufficient 
mechanism. I remember, more than twenty 
years ago, asking this distinguished discoverer 
how it was that the hypothesis arose in his mind. 
He replied that when he was working upon the 
germ-cells of Hydrozoa he realized that he was 
dealing with material which was most carefully 



preserved as if of the most essential importance 
for the species. If the efficient cause of the 
stages of ontogeny resides in the fertilized ovum 
—as we cannot doubt—Weismann’s hypothesis 
satisfactorily accounts for their hereditary trans¬ 
mission. For the portion of the ovum set aside 
to form the germ-cells from which the next gen¬ 
eration will arise is reserved with all its powers 
and includes the potentiality of these stages no 
less than the other inherent characteristics of the 

It is, I think, unfortunate to seek for analogies 
—and vague analogies they must always be— 
between heredity and memory. However much 
we have still to learn about it, memory is, in its 
physiological side, a definite property of certain 
higher cerebral tissues,—a property which has 
clearly been of the utmost advantage in the strug¬ 
gle for life and bears the stamp of adaptation. 
Compare, for instance, the difficulty in remem¬ 
bering a name with the facility in recognizing a 
face. Adaptation would appear to be even more 
clearly displayed in the unconscious registration 
in memory and the instant recognition of another 
individual as seen from behind or when partially 
concealed. Such memory is quite independent 
of the artistic power. Without any intelligent 
appreciation of what is peculiar to another indi¬ 
vidual, his characteristic features are stored up 
unconsciously so that when seen again he is in¬ 
stantly recognized. 



One other consideration brought forward by 
Mr. Francis Darwin may be briefly discussed. 
It is well known that plants have the power of 
adjusting themselves to their individual environ¬ 
ment, and that such adjustment may beneficially 
take the place of a rigid specialization. The 
static condition of plants renders this power espe¬ 
cially necessary for them, and the hereditary 
transmission of the results of its exercise espe¬ 
cially dangerous. Where the seed falls, there 
must the plant grow. The parent was limited to 
one out of many possible environments; the off¬ 
spring may grow in any of them, and for one 
that would hit off the precise conditions of the 
parent and would benefit by inheriting the 
parental response, numbers would have to live in 
different surroundings and might be injured by 
the hereditary bias. 

Mr. Francis Darwin calls attention to the 
leaves of the beech, which in the interior, shaded 
parts of the tree possess a structure different 
from that exhibited in the outer parts more freely 
exposed to light. The structure of the shaded 
leaves resembles that apparently stereotyped in 
trees permanently adapted to shade, and Mr. 
Francis Darwin is inclined to regard the fixed 
condition as a final result of the hereditary trans¬ 
mission of the same response through a large 
number of generations. 

The development of shade foliage in the beech 
is, I presume, a manifestation of a power widely 



spread among animals and probably among plants 
also, a power of producing a definite individual 
adaptation in response to a definite stimulus. 
To stereotype the result would be to convert a 
benefit to the individual into an injury to the 
species. The beech in a very shady place would 
presumably develop the maximum of the shade 
foliage. How disadvantageous would the hered¬ 
itary bias be to its offspring that happened to 
grow in more exposed situations. But, it is 
argued, in plants subject to the fixed condition 
we do meet with the fixed structure, just as if 
repetition had at length produced an hereditary 
result. The answer to this argument seems to 
me to be complete. When conditions are uni¬ 
form and no power of individual adaptation is 
required, Natural Selection, without attaining 
the power, would produce the fixed result in the 
usual way. If, however, a species already pos¬ 
sessing the power, ultimately came to live perma¬ 
nently in one set of conditions and thus ceased 
to need it, the power itself, no longer sustained 
by selection, would sooner or later be lost. 



It is interesting to note that the term “ Muta¬ 
tion ” appears at one time to have suggested itself 
to Darwin 1 in order to express the evolution or 

1 This seems clear from the following passage in a letter 
written February 14, 1845, to Rev. L. Blomefielcl (Jenyns): 
“Thanks for your hint about terms of ‘mutation,’ etc.; I had 



descent with modification of species, by no means 
implying change by large and sudden steps as in 
the usual modern acceptation of the term. In¬ 
deed, the words “ mutable,” “ mutability,” and 
their opposites have never been employed with 
the special significance now attached to “ muta¬ 
tion.” Every one believes in the mutability of 
species, hut opinions differ as to whether they 
change by mutation. 

It is a mistake to suppose that Darwin did not 
long and carefully consider large variations, or 
“ mutations,” as supplying the material for evo¬ 
lution. Writing to Asa Gray as early as August 
11, 1860, he said 1 of great and sudden vari¬ 
ation :— 

“ I have, of course, no objection to this, indeed it 
would be a great aid, but I did not allude to the subject, 
for, after much labor, I could find nothing which satis¬ 
fied me of the probability of such occurrences. There 
seems to me in almost every case too much, too complex 
and too beautiful adaptation in every structure to 
believe in its sudden production.” 

In the twenty years between 1860 and 1880 we 
find that Darwin was continually brought back 
to this subject by his correspondents, and by re¬ 
views and criticisms of his work. Scattered over 

some suspicions that it was not quite correct, and yet I do not 
yet see my way to arrive at any better terms. It will be years 
before I publish, so that I shall have plenty of time to think 
of better words. Development would perhaps do, only it applied 
to the changes of an individual during its growth.” More Letters, 
I, p. 50. 

1 Life and Letters, II, pp. 333, 334. 



this period we find numbers of letters in which he 
expressed his disbelief in an evolution founded on 
“ sudden jumps ” or “ monstrosities,” as well as 
on “ large,” “ extreme,” and “ great and sudden 
variations.” Out of many examples I select one 
more because of its peculiar interest. The Duke 
of Argyll had criticised Darwin’s theory of Nat¬ 
ural Selection as though it had been a theory 
of mutation, an interpretation repudiated by 

The Duke of Argyll in his address 1 to the 
Royal Society of Edinburgh, December 5, 1864, 
had said:—“ Strictly speaking, therefore, Mr. 
Darwin’s theory is not a theory of the Origin of 
Species at all, but only a theory on the causes 
which lead to the relative success and failure of 
such new forms as may be born into the world.” 
In a letter to Lyell (January 22, 1865), Darwin 
wrote concerning this argument of the Duke’s:— 

“ I demur ... to the Duke’s expression of 4 new 
births.’ That may be a very good theory, but it is not 
mine, unless he calls a bird born with a beak 1-100th of 
an inch longer than usual 4 a new birth ’; but this is 
not the sense in which the term would usually be under¬ 
stood. The more I work the more I feel convinced it 
is by the accumulation of such extremely slight varia¬ 
tions that new species arise.” 2 

I desire again to state most emphatically that, 
during the whole course of his researches and re¬ 
flections upon evolution, Darwin was thoroughly 

1 Scotsman, December 6, 1864. 

2 Life and Letters, III, p. 33. 



aware of the widespread large variations upon 
which the mutationist relies. He had the mate¬ 
rial before him, he formed his judgment upon it, 
and on this memorable day it seems specially 
appropriate to show how extraordinarily sure his 
scientific instincts were wont to be. This will 
be made clear by a few examples of the solution 
which Darwin found for problems which at the 
time had either not been attempted at all or had 
been very differently interpreted. 

Darwin’s explanation of coral islands and 
atolls, at first generally accepted, was afterwards 
called in question. Finally, the conclusive test 
of a deep boring entirely confirmed the original 
theory. Perhaps the most remarkable case is 
that of the permanence of ocean basins and con¬ 
tinental areas, a view which Darwin maintained 
single-handed in Europe, although supported by 
Dana in America, against Lvell, Forbes, Wal¬ 
lace, Hooker, and all others who had written on 
the subject. Darwin considered it mere waste 
of time to speculate about the origin of life; 
w r e might as well, he said, speculate about the 
origin of matter. Nothing hitherto discovered 
has shaken this opinion, which is expressed al¬ 
most in Darwin’s words in Professor Arrhenius’ 
recent work . 1 In the fascinating subject of geo¬ 
graphical distribution we now know that Darwin 
anticipated Edward Forbes in explaining the 
alpine arctic forms as relics of the glacial period, 

1 Worlds in the Making. English translation, London, p. 190. 



while he interpreted the poverty of Greenland 
flora and the reappearance of north temperate 
species in the southern part of South America as 
results of the same cause. Almost as soon as the 
facts were before him in Wollaston’s memoirs, 
Darwin had interpreted the number of wingless 
beetles in oceanic islands as due to the special 
dangers of flight. He anticipated H. W. Bates’ 
hypothesis of mimicry, but drove it from his mind 
because he did not feel confident about the geo¬ 
graphical coincidence of model and mimic. Long 
before the Origin appeared Darwin had thought 
over and rejected the idea that the same species 
could have more than a single origin or could 
arise independently in two different countries— 
a hypothesis very popular in later years, but, I 
believe, now entirely abandoned. 

I should wish to advance one consideration be¬ 
fore concluding this section of my address. Cer¬ 
tain writers on mutation seem to hold the view that 
Natural Selection alone prevents large variations 
from often holding the field and leading to great 
and rapid changes of form. Such a view is not 
supported by the history of species which inhabit 
situations comparatively sheltered from the 
struggle, such as fresh water, caves, certain 
islands, or the depth of the ocean. Organisms 
in these places tend to preserve their ancestral 
structure more persistently than in the crowded 
areas where Natural Selection holds more potent 




Darwin fully recognized the limit to the results 
which can be achieved by the artificial selection 
in one direction of individual variations. Thus 
he wrote, 1 August 7, 1869, to Sir Joseph 

44 1 am not at all surprised that Hallett has found 
some varieties of wheat could not be improved in cer¬ 
tain desirable qualities as quickly as at first. All 
experience shows this with animals; but it would, I 
think, be rash to assume, judging from actual experi¬ 
ence, that a little more improvement could not be got 
in the course of a century, and theoretically very 
improbable that after a few thousands [of years’] rest 
there would not be a start in the same line of variation.” 

The conception of evolution hindered or for a 
time arrested for want of the appropriate varia¬ 
tions is far from new. The hypothesis of organic 
selection was framed by Baldwin, Lloyd Mor¬ 
gan, and Osborn to meet this very difficulty, as 
expressed in the following paragraph quoted 
from the present writer’s address to the Amer¬ 
ican Association for the Advancement of Science 
at the Detroit meeting, October 15, 1897:— 

44 The contention here urged is that natural selection 
works upon the highest organisms in such a way that 
they have become modifiable, and that this power of 
purely individual adaptability in fact acts as the nurse 
by whose help the species . . . can live through 

1 More Letters, I, p. 314. 



times in which the needed inherent variations are not 
forthcoming.” 1 

It has already been shown that Darwin entirely 
recognized the limits which the variations now 
called “ fluctuating ” may set to the progress 
achieved by artificial selection, and that he ad¬ 
mitted the necessity of waiting for a fresh “ start 
in the same line.” In this respect he agreed with 
modern writers on mutation; but differed from 
them, as has been already abundantly shown, in 
the magnitude assigned to the variations form¬ 
ing the steps of the onward march of evolution. 
His observation and study of nature led him to 
the conviction that large variations, although 
abundant, were rarely selected, but that evolu¬ 
tion proceeded gradually and by small steps,— 
that it was “ continuous,” not “ discontinuous.” 

In his presidential address 2 to the British As¬ 
sociation at Cape Town in 1905, Sir George 
Darwin brought forward the following argument 
from analogy against the “ continuous transfor¬ 
mation of species ”:— 

“ In the world of life the naturalist describes those 
forms which persist as species; similarly the physicist 
speaks of stable configurations or modes of motion of 
matter; and the politician speaks of States. The 
idea at the base of all these conceptions is that of 
stability, or the power of resisting disintegration. In 
other words, the degree of persistence of permanence 
of a species, of a configuration of matter, or of a State 

1 Development and Evolution. J. M. Baldwin, New York, 1902, 
p. 350. 

3 Report British Association } 1905, p. 8. 



depends on the perfection of its adaptation to its sur¬ 
rounding conditions.” 

After maintaining that the stability of states 
rises and declines, culminating when it reaches 
zero in revolution or extinction, and that the 
physicist witnesses results analogous with those 
studied by the politician and the historian, the 
author continues:— 

“ These considerations lead me to express a doubt 
whether the biologists have been correct in looking for 
continuous transformation of species. Judging by 
analogy we should rather expect to find slight con¬ 
tinuous changes occurring during a long period of 
time, followed by a somewhat sudden transformation 
into a new species, or by rapid extinction.” 1 

I do not, of course, doubt that there is reality 
in the analogy between the evolution of states 
and of species, hut it is not, I submit, close 
enough to justify the author’s reasoning from 
one to the other. The communities of the social 
Hymenoptera present much closer analogies with 
political states, and yet even here it would be 
unjustifiable to infer that the evolution of insect 
societies has been discontinuous. 

1 The following footnote is appended to Sir George Darwin’s 
address:—“ If we may illustrate this graphically, I suggest that 
the process of transformation may be represented by long lines 
of gentle slope, followed by shorter lines of steeper slope. The 
alternative is a continuous uniform slope of change. If the 
former view is correct, it would explain why it should not be 
easy to detect specific change in actual operation. Some of my 
critics have erroneously thought that I advocate specific change 
per saltum.” 

In reply to this note it may be pointed out that " per saltum 
evolution ” or “ discontinuous evolution ” differs from “ continu¬ 
ous evolution ” only in the steepness of the slope of change. 



The analogy seems to me far looser between the 
changes of configuration of matter witnessed by 
the physicist and the modification of a species as 
a result of the struggle with its organic environ¬ 
ment. The essential characteristics by which the 
evolutionary history of the organic world di¬ 
verges widely from that of the inorganic is very 
clearly stated in the following brief passage from 
a letter 1 written by Charles Darwin to Sir Jo¬ 
seph Hooker, on November 23, 1856, just three 
years before the publication of the Origin : — 

“ Again, the slight differences selected, by which a 
race or species is at last formed, stands, as I think can 
be shown (even with plants, and obviously with animals), 
in a far more important relation to its associates than 
to external conditions. Therefore, according to my 
principles, whether right or wrong, I can not agree 
with your proposition that time, and altered conditions, 
and altered associates, are 4 convertible terms.’ I look 
at the first and last as far more important, time being 
important only so far as giving scope to selection.” 


That the Origin of Species , which Darwin de¬ 
scribed as undoubtedly the chief work of his life , 2 
should have been bitterly attacked and misrepre¬ 
sented in the early years of the last half century, 
is quite intelligible; but it is difficult to under¬ 
stand the position of a recent writer who main¬ 
tains that the book exercised a malignant influ- 

1 Life and Letters, II, p. 87. 

2 Life and Letters of Charles Darwin, I, p. 86. 



ence upon the interesting and important study 
of species and varieties by means of hybridism. 
As regards these researches its appearance, we 
are told, “ was the signal for a general halt 1 
upon them Natural Selection “ descended like a 
numbing spell 2 and if we are still unsatisfied 
with his fertility in metaphor the author offers a 
further choice between the forty years in the wil¬ 
derness, 3 and the leading into captivity. 4 

Francis Galton, in his address as a recipient 
of the Darwin-Wallace medal on July 1st last, 
recalled the effect of the Linnean Society Essay 
and the Origin. The dominant feeling, he said, 
was one of freedom. This liberty was offered to 
the student of hybridism as freely as to any other. 
No longer brought up against the blank wall of 
special creation, he could fearlessly follow his re¬ 
searches into all their hearings upon the evolution 
of species. And this had been clearly foreseen 
by Darwin when, in 1837, he opened his first 
note-book and set forth the grand program which 
the acceptance of evolution would unfold. He 
there said of his theory that “ it would lead to 
study of . . . heredity,” that “ it would lead 
to closest examination of hybridity and genera¬ 
tion.” In the Origin itself the admirable re¬ 
searches of Ivolreuter and Gartner on these very 
subjects received the utmost attention and were 

1 Report British Association, 1904, p. 575. 

8 L. c., p. 576. 

8 MendeVs Principles of Heredity , W. Bateson, 1902, p. 104, 

4 L. c., p. 208. 



brought before the world far more prominently 
than they have ever been either before or since. 
Furthermore, the only naturalist who can be de¬ 
scribed as a pupil of Darwin’s was strongly ad¬ 
vised by him to repeat some of Gartner’s experi¬ 
ments . 1 It is simply erroneous to explain the 
neglect of such researches as a consequence of 
the appearance of the Origin and the study of 
adaptation. So far from acting as a “ numbing 
spell ” upon any other inquiry, adaptation itself 
has been nearly as much neglected as hybridism, 
and for the same reason—the dominant influence 
upon biological teaching of the illustrious com¬ 
parative anatomist Huxley, Darwin’s great gen¬ 
eral in the battles that had to be fought, but not 
a naturalist, far less a student of living nature. 

The momentous influence of the Origin upon 
the past half century, as well as that strange lack 
of the historic sense which alone could render pos¬ 
sible the comparisons I have quoted, require for 
their appreciation the addition of yet another 
metaphor to the series we have been so freely 

The effect of the Origin upon the boundless 
domain of biological thought was as though the 
sun had dispelled the mists that had long en¬ 
shrouded some vast primeval continent. It 
might then perhaps be natural for some primitive 

1 Darwin’s letter of December 11, 1862, to John Scott, contains 
the following words: “If you have the means to repeat Gartner’s 
experiments on variations of Verbascum or on maize (see the 
Origin ), such experiments would be preeminently important.” 



chief to complain of the strong new light that was 
flooding his neighbor’s lands no less than his own, 
thinking in error not inexcusable at the dawning 
of the intelligence of mankind, that their loss 
must be his gain. 

And now in my concluding words I have done 
with controversy. 

Fifty years have passed away, and we may he 
led to forget their deepest lesson, may be tempted 
to think lightly of the follies and the narrow¬ 
ness, as they appear to us, of the times that are 
gone. This in itself would be a narrow view. 

The distance from which we look back on the 
conflict is a help in the endeavor to realize its 
meaning. Huxley’s Address on The Coming of 
Age of the Origin was a pasan of triumph. Tyn¬ 
dall, his friend, further removed from the strug¬ 
gle by the nature of his life-work, realized its 
pathos when he spoke in his Belfast Address of 
the pain of the illustrious American naturalist 
who was forced to recognize the success of the 
teachings he could not accept,—the naturalist 
who dictated in the last year of his life the 
unalterable conviction that these teachings were 

I name no names, but I think of leaders of 
organic evolution in this continent and in Europe, 
—sons of great men to whom the new thoughts 
brought the deepest grief, men who struggled 
tenaciously and indomitably against them. And 
full many a household unknown to fame was the 



scene of the same poignant contrast, was torn by 
the same dramatic conflict. 

We have passed through one of the world’s 
mighty bloodless revolutions; and now, standing 
on the further side, we survey the scene and are 
compelled to recognize pathos as the ruling 

The sublime teachings which so profoundly 
transformed mankind were given by Him who 
came not to bring peace on earth but a sword. 
And so it is in all the ages with every high cre¬ 
ative thought which cuts deep into “ the general 
heart of human kind.” It must bring when it 
comes division and pain, setting the hearts of the 
fathers against the children and the children 
against the fathers. 

The world upon which the thoughts of Dar¬ 
win were launched was very different from the 
world to which were given the teachings of Gal¬ 
ileo and the sublime discoveries of Newton. The 
immediate effect of the first, although leading to 
the bitter persecution of the great Italian, was 
restricted to the leaders of the Church; the influ¬ 
ence of the second was confined to the students of 
science and mathematics, and was slow in pene¬ 
trating even these. Nor did either of these high 
achievements of the human intellect seriously 
affect the religious convictions of mankind. It 
was far otherwise with the teachings of the Origin 
of Species; for in all the boundless realm of phi¬ 
losophy and science no thought has brought with 



it so much of pain, or in the end has led to so 
full a measure of the joy which comes of intel¬ 
lectual effort and activity as that doctrine of 
Organic Evolution which will ever be associated, 
first and foremost, with the name of Charles 
Robert Darwin. 





The indebtedness of Botany to Charles Dar¬ 
win extends beyond his formulation of the theory 
of the origin of species by Natural Selection. 
His historical position in plant physiology and 
in plant ecology is one of first rank, which these 
phases of Botany have often gratefully acknowl¬ 
edged. As for the theory of Natural Selection, 
its relation to the development of modern plant 
morphology is still more fundamental. It is true 
that about ten years before the appearance of 
the Origin of Species, Hofmeister had given to 
modern plant morphology its first great impulse 
in his demonstration of the essential relationships 
among higher plants; but the announcement of 
the theory of Natural Selection suggested a 
modus operandi for the plant phylogeny that 
may be said to have been established. Among 
plants, the facts and an outline of phylogeny 
for the application of any theory of descent had 
been secured, so that Natural Selection came to 
plant morphology at the psychological moment. 
It is no wonder that it was received by plant mor- 





phologists with eagerness, and that it stimulated 
tremendously the type of investigation initiated 
chiefly by Hofmeister. Whether Natural Selec¬ 
tion stands or falls as an adequate explanation of 
the origin of species, there can never be any doubt 
as to the breath of life it infused into the young 
science of phylogenetic plant morphology. 

I am in no position to state whether from the 
standpoint of Botany the theory of Natural Se¬ 
lection presents any more difficulties or probabil¬ 
ities than it does from the standpoint of Zoology. 
The literature of the theory in its application to 
animals is so vast, and has become so special, that 
no botanist can he expected to compass it intelli¬ 
gently. The present series of papers may make 
this situation clear; and yet I cannot presume to 
speak for botanists in general, among whom there 
is great diversity of opinion. I can only express 
the opinion of an individual botanist who has had 
some experience in dealing with the facts that 
enter into the construction of phylogenies. 


When the botanist confines his attention to a 
wide-ranging genus of numerous species, as the 
genus Aster in North America, for example, the 
origin of these species by Natural Selection 
would seem to be an adequate explanation of the 
situation. The variations are endless and in 



every direction, the intergrades are innumerable, 
the habitats are exceedingly diverse, and Natural 
Selection would seem to necessitate just the re¬ 
sult observed. In fact, the greatest American 
student of the genus, after a prolonged effort to 
detect and define the boundaries of its species, 
gave it as his private opinion that “ there are no 
species in Aster.” Of course this must be under¬ 
stood as an expression of despair rather than of 
belief, hut it emphasizes the situation. With the 
wide-ranging genera showing this condition, it 
was not difficult to imagine that the sharp differ¬ 
ences among isolated species are to be explained 
by the breaking up of their continuity; and so all 
species were swept into the category of Natural 

On the other hand, when the botanist came to 
enlarge the horizon of his observation, and in¬ 
cluded the whole phylogeny of some great group 
of plants, or even the phylogeny of the whole 
plant kingdom, he began to have doubts as to the 
adequacy of Natural Selection as an explanation 
of all the changes. ITe has learned to regard this 
selection as a factor that perpetuates and perhaps 
develops certain characters, and that eliminates 
others; but he cannot discover how it can really 
originate new characters. The genus Aster, for 
example, is defined by a definite group of char¬ 
acters; and the species may be regarded as the 
selected variants of these same characters. The 
pattern changes, as in the kaleidoscope, but noth- 



ing new has entered into any combination. But 
when the Aster boundary is crossed, and still 
more when the boundaries of Composite and 
then of Angiosperms are crossed, absolutely new 
characters are met on every hand; and still the 
phylogenetic connections seem convincing. For 
example, perhaps no plant morphologist doubts in 
these days that at least some of the Gymnosperms 
are phylogenetically related to ancient ferns. The 
distinguishing mark between the two groups is 
the absence of seeds in the one and their presence 
in the other. The seed and all that goes with it 
is a new character, and how selection could have 
originated it, is a question at whose answer even 
scientific imagination balks. It is evident that 
the ovules of Gymnosperms are related by de¬ 
scent to the sporangia of ferns in some way, but 
so extensive a change does not seem to come 
within the possibilities of Natural Selection. We 
have relatively primitive ovules, but they are 
enormously different from fern sporangia; and 
we can imagine how selection may have trans¬ 
formed these ovules into those of more advanced 
type, for this is only manipulating a structure 
already in existence and is adding nothing new. 
The leaves of sporophytes, the vascular system, 
the root system are further illustrations of the 
same kind. Absolutely unrepresented in the 
lower groups, they are new, complex, and fully 
functioning structures when we meet them first. 
Of course lost records and an inconceivable lapse 



of time are the usual answers, but they do not 
save us from doubt. 

In brief, by the botanist who has brought to¬ 
gether a wide range of material, natural selection 
might be accepted as having variously arranged 
a group of established characters, and in this 
sense given rise to what we call species; but it 
could not be accepted so easily as originating 
such new characters as distinguish great groups. 
In a certain sense, of course, there is nothing new, 
or else there would be no phylogeny; but as we 
use the word character , it often appears as a new 
thing in passing from one great group to another 
one presumably derived from it. 


To the botanist, the greatest immediate diffi¬ 
culty with Natural Selection has probably come 
from the idea of adaptations associated with it. 
For a time he was captivated with the idea, and 
much botanical literature testifies to the fact. 
As he then understood it, nature selected those 
forms that are best adapted to their environment, 
and destroyed those that are less adapted. This 
meant that the characters of the forms selected 
for survival must show some fitness for the envi¬ 
ronment, and great ingenuity was displayed in 
explaining this fitness. Then came the new sub¬ 
ject ecology and its associate experimental mor¬ 
phology, and the old explanations began to 



For example, the character of thorns was said 
to be selected because their presence was a pro¬ 
tection against grazing animals. Now it is 
known that thorns chiefly prevail among plants 
in regions peculiarly free from grazing animals; 
and that even if the grazing animals are present 
the thorns do not appear in the early stages of the 
plant, when they are most needed. Conversely, 
the plants chiefly attacked by grazing animals are 
singularly free from thorns. Experimental work 
has shown that many thorns are a response to 
poor nutrition, and that they may or may not be¬ 
come an established character. 

The elaborate stinging hairs of the nettle rep¬ 
resent a character that according to this view 
was built up by Natural Selection, with adapta¬ 
tion as the principle of selection. Now it is 
known that the nettle is indifferent to their pres¬ 
ence and gets along without them. 

It is a well-known fact that many seeds, espe¬ 
cially those of arid regions, develop a testa so 
hard that it interferes with the breaking through 
of the embryo. In fact, it is becoming evident 
that if selection is working in these cases it is 
working towards “ over-adaptation.” 1 

A difficulty is also presented by such structures 
as the velamen of the aerial orchids, as well as 
by the water-conducting vessels of the vascular 
system. In both of these cases the structures do 

1 This situation has been developed by the recent studies of 
the germination of seeds and spores by Dr. William Crocker of 
the University of Chicago. 


not perform their very important functions until 
the cells are dead. Just how a group of dead 
cells, performing a mechanical function, could 
have been built up by Natural Selection, is hard 
to imagine; and yet, in the case of the vascular 
system its presence is a fundamental distinction 
between two great divisions of the plant king¬ 

A striking illustration of the change of view 
that plant structures are necessarily useful be¬ 
cause they have been selected on account of adap¬ 
tation has been developed by a very recent inves¬ 
tigation of extra-floral nectaries, 1 which included 
an examination of 100 species of plants growing 
in the Botanic Gardens of Buitenzorg, Java. 
The view in reference to many of these extra¬ 
floral nectaries has been that they attract ants, 
which in turn defend the host plant from its ene¬ 
mies. Hence we have such a category of plants 
as myrmecophiles, or “ ant-loving plants.” Dar¬ 
win himself naturally believed in myrmecophiles, 
and Kerner included them among his illustrations 
of protection against “ unbidden guests.” Now 
it appears that any such use for these remark¬ 
able organs is untenable; and there are many 
facts that suggest that they have no definite pur¬ 
pose that could be laid hold of as an adaptation. 
The secretion often begins late in the life of the 
plant, so that any protection it affords is lacking 

1 Nieuwenhuis von Uxkull-Giildenbandt, M.: “ Extraflorale 

Zuckerausscheidungen und Ameisenschutz,” Ann. Jard. Bot. Bui¬ 
tenzorg, II, 6; pp. 195-327. 1907. 



when most needed. In some cases the secretion 
begins at a very early stage of the plant and soon 
fails, leaving the maturing and adult plants un¬ 
protected. The nectaries secrete spasmodically 
and are often dry; and the nectar of many forms 
is avoided by ants and other animals. There is 
no relation between mutilated flowers, ants, and 
extra-floral nectaries. Most mutilated flowers 
produce as many seeds as those that are not; and 
the honey-seeking ants are not combative and do 
not attack other insects visiting their host. If 
these extra-floral nectaries have been developed 
and perpetuated by Natural Selection, it is an 
illustration of the selection of harmful structures, 
for they often attract insects of all kinds, which 
damage the plant in various ways. The investi¬ 
gation showed that individual plants which se¬ 
crete little or no nectar are less harmed by insects 
than are those that produce nectar. 

It is such work that is playing havoc with the 
“ adaptations ” of botanical literature, and is 
forcing botanists to see in these various structures 
inevitable responses to conditions that have noth¬ 
ing to do with adaptation. It would be going 
too far to say that such results destroy absolutely 
all faith in the selection and development and fix¬ 
ing. of adapted structures, but they do tend to 
weaken faith and to demand that every claimed 
case shall be subject to rigid experimental inves¬ 
tigation. That there must be selection no one 
pretends to deny, so far as I know, but when the 



selection includes unfavorable as well as favor¬ 
able characters, it seems to have lost its motive. 

And still, behind all this uncertainty as to the 
selection and perpetuation of small variations, as 
to whether this kind of indiscriminate selection 
can result in anything so definite as distinct spe¬ 
cies, there is clearly evident the large fact of the 
evolution of the plant kingdom, which has be¬ 
come a more difficult problem than ever before. 
To observe and explain the small results, which 
are the only kind that can be brought under the 
absolute control of modern investigation, seems 
to result in obtaining a measuring rod too short 
to apply to general phylogeny; and the more con¬ 
fusing are our experimental results, the larger 
becomes the error that is multiplied by the gen¬ 
eral application. 

So far as I am acquainted with the opinions 
of botanists whose work has to do with structures 
and phenomena involved in evolution, there seems 
to be a general feeling that Natural Selection 
does not select individual plants on the basis of 
some small and better adapted variation, and so 
build up a character, which with its associates 
will gradually result in a closely allied new spe¬ 
cies; but that its selection of individuals seems 
to hold no relation to their useful characters. On 
the other hand, there is general conviction that 
Natural Selection determines what species shall 
survive, simply by eliminating those that do not. 
Applying this to a general phylogeny, Natural 



Selection becomes a factor of enormous impor¬ 
tance; for the species that survive determine, 
within limits, the species to be produced. 


A general illustration of this point of view may 
be taken from the phylogenetic relationships 
among Gymnosperms. This ancient group 
stands among plants as one of remarkable rigid¬ 
ity. Land plants should be more plastic than 
land animals, for they must remain fixed in a 
given environment, while animals can shift their 
environment when the pressure of change comes. 
A striking contrast between the taxonomic char¬ 
acters used by zoologists and those used by bot¬ 
anists is brought out here. Among botanists, the 
taxonomic characters in most general use are 
those that respond with least promptness or not 
at all to changing environment; while among 
zoologists, as I am informed, the taxonomic char¬ 
acters in most general use largely fall in the cat¬ 
egory of so-called “ adaptation ” characters, 
which had far better be called “ response ” char¬ 
acters. For this very reason, I can easily imag¬ 
ine that there should be more supporters of Nat¬ 
ural Selection among zoologists than among bot¬ 

Be this as it may, Gymnosperms seem to be 
about the least plastic of land plants, certainly 
the least plastic of any great group. Even the 



number of chromosomes, which in some groups 
of plants may vary from species to species, seems 
to be practically a fixed number in the whole 
assemblage. There seems to be among them lit¬ 
tle or no visible response in nature to changing 
conditions of the most extreme kinds. It would 
seem that selection among these relatively inva¬ 
riable forms can hardly be more than the accident 
of crowding. Certainly one can lay hold of no 
kind of variation in nature that even suggests 
the coming characters of another species, much 
less of another genus or family. And yet the 
group as a whole shows that certain distinct evo¬ 
lutionary tendencies have been worked out in a 
progressive way. Students of the group may 
differ as to the details of the phylogenetic his¬ 
tory, but there is no difference of opinion as to 
its general features. Some of these general fea¬ 
tures may be instructive in this connection. 

The plant which produces the female sex or¬ 
gans, known as the female gametophyte, is not 
only in the midst of an ovule invested by a thick 
integument, but is also directly inclosed by the 
heavy wall of the megaspore that produced it. 
If any structure is shut away from the influences 
of a changing environment, it would seem to be 
this one. And yet, through the whole series of 
Gymnosperms, this gametophyte shows a pro¬ 
gressive transformation. In the most primitive 
forms it matures as a relatively large mass of 
tissue, and late in its history the female sex organs 



(archegonia) appear. In the first stage of its 
development it consists of a large number of free 
nuclei; in the second stage walls appear and a 
tissue is formed; and in the last stage this tissue 
grows and finally produces the archegonia with 
their egg. The constant tendency throughout 
the whole group is to produce the female sex 
organs earlier and earlier in the history of the 
gametophyte. A series can be arranged illus¬ 
trating the appearance of the sex organs at what 
might be called the mature stage of the gameto¬ 
phyte, at one extreme; then their appearance at 
earlier and earlier stages of the tissue develop¬ 
ment, until they appear with the first formation of 
walls; and finally, at the other extreme, the eggs 
appear at the stage of free nuclei, so that no sex 
organs are formed. This progressive slipping 
back of the egg in the ontogeny of the gameto¬ 
phyte holds no relation to any advantage that can 
he detected. Certainly it holds no relation to 
any advantage in fertilization, for that is a pro¬ 
longed process among Gymnosperms, and the 
pollen tube containing the sperms may live for a 
season or two in the tissues of the ovule. Taking 
the group as a whole, this is not a sporadic 
change, occurring here and there; hut the two 
extremes I have given are the two extremes of 
the Gymnosperm phylum. This kind of progres¬ 
sive change is beyond the reach of experiment, 
and its explanation is beyond the reach of imagi¬ 
nation as yet. 



The same kind of progressive change is shown 
also in the embryo of Gymnosperms. In the 
most primitive condition, the first stage of em¬ 
bryo formation is extensive free nuclear division 
within the fertilized egg; after this, walls are 
formed and the egg becomes filled with tissue, 
the proembryo. Throughout the Gymnosperm 
series there is a steady reduction of the amount 
of free nuclear division, and with it a reduction 
of the amount of proembryonic tissue, so that 
finally it occupies a very small portion of the fer¬ 
tilized egg. All this change has taken place fur¬ 
ther from outside influences than the change in 
the gametophyte, for the embryo is imbedded in 
the gametophyte. 

It may be claimed that these are not the char¬ 
acters that taxonomists use in distinguishing spe¬ 
cies. This is true, but they are just the charac¬ 
ters that distinguish great groups, and represent 
the advancement of the plant kingdom as a whole. 
It so happens that both of the progressive 
changes noted as occurring among Gymnosperms 
culminate among Angiosperms. 

The male gametophyte of Gymnosperms 
shows a similar progressive change, not so steady, 
but none the less evident. Its few cells are con¬ 
tained within the resistant wall of the pollen 
grain which produces it. In the more primitive 
condition the vegetative cells are variable in num¬ 
ber, but evident; but there is a persistent tend¬ 
ency to eliminate them, which reaches comple- 



tion in certain Gymnosperms, and is a constant 
feature of Angiosperms. 

It may be said that in all these cases we are 
dealing with structures that have ceased to be 
useful, and therefore are being gradually elim¬ 
inated. No one can say how useful they are, but 

that they are functional. But 
there is a striking illustration of another sort 
among Gymnosperms. The suspensor is a con¬ 
spicuous organ of the embryo in this group, with 
a development apparently out of all proportion 
to its usefulness. In fact, it is a most exagger¬ 
ated structure, often becoming closely coiled on 
account of its extreme length. One would sup¬ 
pose that this would be the first structure 
eliminated, or at least curtailed, if usefulness de¬ 
termines suppression. But the suspensor of 
Gymnosperms shows no symptom of suppression 
throughout the whole group, and still among the 
heterosporous Pteridophytes below and the An¬ 
giosperms above, where the same conditions pre¬ 
vail, it shows no such unusual development. 

Several illustrations could be taken from Gym¬ 
nosperms, all of them fundamental in the struc¬ 
ture and progress of the group, and none of them 
in use by taxonomists. My claim is that it may 
be one thing to pass from species to species within 
the limits of a small natural group; and a very 
different thing to pass from one great group to 
another. I do not doubt that the characters of 
a genus may have been juggled in a variety of 

no one can deny 



ways to form what we call its species, and that 
one of these ways may have been Natural Selec¬ 
tion, with or without adaptation. Our problem, 
however, includes more than the origin of species. 
All of our observation and experimental work in 
this field is immensely important in demonstrat¬ 
ing the theory of descent, and in showing how the 
final diversity of species is reached; but the meth¬ 
ods for securing this final diversity may not apply 
and probably do not apply to the establishment 
of the assemblages of different characters that 
distinguish the great groups, and that any study 
of phylogeny shows to have been wrought out 
by steady and progressive change through all im¬ 
aginable changes of environment. Species have 
been likened to the individual waves that appear 
on the surface of a choppy sea; if so, the deep- 
seated changes to which I refer, and which phy¬ 
logeny makes so evident, may be likened to the 
great oceanic currents, whose movement and 
direction proceed with no relation to the choppy 




By isolation, segregation or separation as a 
factor in evolution, we mean the failure of a por¬ 
tion of one group or species to interbreed freely 
with the rest of its kind. Such failure is due to 
the presence of some harrier which prevents free 
intermingling of individuals or to some condition 
or group of conditions which sets certain indi¬ 
viduals off from the mass of their kind. Through 
separations of this sort race distinctions arise, 
and in time by the same means the more profound 
modifications which mark what w r e call species. 
The occasion of divergence in most cases is found 
in geographical separation, the “ raiimliche Son- 
derung,” on which such strong emphasis has been 
justly laid by Moritz Wagner. It may again 
be a separation of some other kind, as segrega¬ 
tion, through the occupation of different tracts 
within the same general area, or seasonal separa¬ 
tion, as when flowers bloom or animals mate at 
different times of the year. There are also forms 
of physiological segregation. Self-fertilized 
plants mate with their neighbors irregularly or 
by chance, the pure species standing alongside of 



hybrids or quasi-hybrids. Dr. Shull informs us 
that several such cases occur in the flora of Cali¬ 
fornia. A race or species of higher animals may 
develop dislikes or infertilities with forms other¬ 
wise nearly related. Caton tells us that this is 
true of deer, which will not cross with other spe¬ 
cies unless “ demoralized,” or relieved of race 
antipathy, by enforced association. 


Free interbreeding tends to unify or obliterate 
forms which are fertile with each other. Isola¬ 
tion in any form tends to check this process, and 
hence in negative fashion works to create new 
forms based on distinctions arising through nat¬ 
ural variation and retained through heredity. 
From this fact arises the rule that closely related 
forms or nascent species do not as a rule inhabit 
or rather breed in the same area. This proposi¬ 
tion has been termed by Dr. J. A. Allen “ Jor¬ 
dan’s Law of Geographical Distribution.” 

The law or generalization has been stated as 

“ Given any species (or kind) in any region, the near¬ 
est related species (or kind) is not to be found in the 
same region, nor in a remote region, but in a neigh¬ 
boring district separated from the first by a bar¬ 
rier of some sort, or at least by a belt of country, 
the breadth of which gives the effect of a barrier.” 

This law holds good as a general rule among 
animals. The only exceptions yet indicated are 



found among plants in which cross-fertilization 
is not general, among Protozoa and other low 
forms in which specific distinctions are unknown 
or at least obscurely shown, in cases of isolation 
other than geographical, and in a few cases which 
seem to be explainable on the ground of re- 
invasion. It is possible that species once thor¬ 
oughly separated through some form of geo¬ 
graphical segregation may later invade the terri¬ 
tory, the one of the other, without crossing or 
hybridization. This seems likely to occur among 
plants, and it is possible among migratory ani¬ 
mals also. Taking the world over, re-invasion is 
probably not a rare phenomenon, although in 
most cases the invading species may fail to estab¬ 
lish itself. In the case of animals dependent on 
man, we find sometimes a form of political segre¬ 
gation, which may lead to the separation of races 
without actual physical barriers. The races of 
sheep in England, for example, go by counties. 
The artificial boundary of a county is a barrier 
to man, rather than to the sheep. In all forms 
of artificial selection, a corresponding degree of 
artificial segregation is always implied and, with¬ 
out segregation, selection has no effectiveness in 
race-forming. Nothing, for example, can be 
done for the race improvement of fishes, unless 
these can be segregated in artificial ponds, away 
from the unselected mass of the species. 




Isolation, as a factor in evolution, represents 
the failure of a species to unify itself or to main¬ 
tain a homogeneous character among its mem¬ 
bers. Within a unified species, each member will 
be fertile with any other of the opposite sex. In 
time, the descendants of any one may cross with 
descendants of all the others, thus bringing all 
individuals to that degree of common relation¬ 
ship implied by membership in a common species. 
Wherever inter-crossing is checked along any 
line, a part of the individuals will be set off from 
the mass, and here divergence at once begins. 
One cause of divergence may lie in the fact that 
in each isolated group there is some original de¬ 
viation from the average of the common stock, 
thus giving at the start some slight difference in 
heredity. But this is purely hypothetical and it 
is not probable in any special case. Other and 
apparently more potent causes of divergence lie 
in the difference of experiences to which each 
group is exposed. The stress of the struggle for 
existence is never quite the same in different lo¬ 
calities, and the nature of selection must vary 

That notable differences obtain in time, even 
in pure stocks, and when there is no visible reason 
for change, is clearly shown in the experience of 
stock breeders. Of this, a typical example will 
suffice. Darwin tells us that the two flocks of 



Leicester sheep, those of Mr. Buckley and of Mr. 
Burgess, were “ purely bred from the original 

years.” There is 
not a suspicion of a single instance of deviation 
from the pure Bakewell Leicester breed in either 
flock. Yet after fifty years the difference in the 
flocks of sheep is so great that they “ have the 
appearance of being quite different varieties.” 
In nature, as in domestication, individuals of the 
same race, animals or plants, prevented from 
inter-crossing for a long time, present at least the 
appearance of distinct varieties or species. A 
study of the weeds of the world, as they have 
spread from place to place, should show this fact 
in interesting fashion. It can also be shown by 
a comparative study of dogs or horses. Mr. 
Vernon Bailey tells me that in the pouched 
gophers and other rodent groups each valley has 
its individual peculiarities, those shown in the 
skulls as well as in the forms or colors of the ani¬ 
mals. All these variations, too small to justify 
the use of technical names, form the beginnings 
of difference in subspecies. With more perfect 
isolation these characters would soon assume 
greater importance. They seem to indicate the 
beginning of species-forming. 

So far as species in nature are concerned, we 
can account for the origin of none of them, except 
on the ground of the presence of some forms of 
isolation. In those groups of animals or plants 
which have been most studied, subspecies or vari- 

stock of Mr. Bakewell for fifty 



eties are recognized only as a geographical lim¬ 
itation can be shown. 

The known facts fully justify the statement 
by Dr. A. E. Ortmann that:— 

“ The four factors named, variation, inheritance, 
selection, and separation, must work together to form 
different species. It is impossible to think that one of 
these should work by itself, or that one could be left 

To use a convenient analogy, the movement of 
organic evolution may be compared to the course 
of a stream. Isolation is the rocky ledge which 
does nothing, but whose resistance must deter¬ 
mine the direction of the river’s flow. Selection 
is the force that drives the stream along, and vari¬ 
ation and heredity lie inherent in the nature of the 
stream of life itself. All of these are necessary 
in bringing about the final result, whatever that 
may be. With these there are doubtless other 
facts, extrinsic and intrinsic, but in this world of 
varied contour and of prodigal reproduction, no 
organism, whatever its heredity or its variations, 
can escape these limiting environmental condi¬ 
tions. Whatever takes part in the final result 
must be a factor in evolution, whether it be an 
initial factor in variation or not. 

In the belief of the writer, the minor differ¬ 
ences which separate species and subspecies 
among animals and plants, in so far as these are 
not traits of adaptation (and most of them are 
clearly not such), owe their existence to some 



form of isolation or segregation. By the effect of 
some form of barrier the members of one group 
are prevented from interbreeding with those of 
another minor group or with the mass of the 
species. As a result, from difference of parent¬ 
age, or difference in selection, or from difference 
in the trend of development, whatever its cause, 
local peculiarities arise. “ Migration,” says Dr. 
Coues (and by this he means the shifting of hab¬ 
itation), “holds species true; localization lets 
them slip or, rather, localization leaves them in 
differing conditions in the general process of av¬ 
eraging up the mass of the species. The peculi¬ 
arities of the parents in an isolated group become 
intensified by in-breeding. These peculiarities 
become modified in some continuous direction by 
the selection induced by the characteristics of 
the local environment. They may possibly be 
changed, as some have imagined, in one way or 
another, by germinal reactions induced by impact 
of environment. It may be that change of envi¬ 
ronment sometimes excites germinal variation. 
In any event, a new form is sooner or later inev¬ 
itable if the segregation is complete. This new 
form is never coincident in range with the parent 
species, nor with any other closely cognate or 
germinate form. Neither is it likely to be found 
in some remote part of the earth. The details 
of its distribution will be determined by the na¬ 
ture of the organism and by its relation to its 
environment. The struggle for existence is a 



very different matter in different parts of the 
world of life. The competition with like forms, 
the struggle with unlike forms, the compromise 
with hard conditions of life, all these change at 
every angle, and the character of Natural Selec¬ 
tion changes with them. The individual animals 
are mobile, as plants are not. They shift about 
and occupy their range more perfectly, while in 
plants their pollen and their seed have great ad¬ 
vantages over animals. With a plant everything 
depends on where its seed is dropped. Where 
an animal is born or hatched is a matter of rela¬ 
tive indifference. With plants, some seed is sure 
to reach almost every available point within the 
range of the species, while the vast majority of 
seeds never have a chance to germinate. All 
these, and every other point of difference, be¬ 
tween one group of organisms and another, affect 
the nature and relative value of the different fac¬ 
tors in divergence. They tend also to obscure 
the laws of distribution. But no law is invali¬ 
dated by the occurrence of exceptions which come 
under some other rule or law. 

The obvious immediate factor in the splitting 
apart of races or species is, therefore, in all 
groups, that of isolation. Behind this lies the 
primal factor of variation, continuous or discon¬ 
tinuous. Fluctuation, saltation or mutation, all 
these are one for the purposes of our present dis¬ 
cussion. With these come the factor of heredity 
and the factor of selection, to which we must 



ascribe all adaptive changes and apparently no 
others. Selection alone does not produce new 
species, although it may continuously modify old 
ones. Usually related species become modified 
in parallel fashion by selection. Through adap¬ 
tations to special surroundings, selection may 
produce convergence of characters, often of such 
a character as to give a semblance of real homol¬ 
ogy. The selection of the desert gives the horned 
toad resemblance to the cactus; this deceives no 
one. But it may give one cactus a deceptive 
resemblance to another which is forced to adapt 
itself to exactly the same conditions. 

It is not often that one species is distinguished 
from another by adaptive characters, or by any 
conceivable difference in fitness to the same con¬ 
ditions in life. In this regard all are fit, and the 
process of natural selection holds each one close 
to its possible limit so long as conditions remain 



The formation of different breeds of sheep 
through isolation and unconscious selection in the 
different counties of England, as elsewhere de¬ 
scribed by the writer, is apparently exactly par¬ 
allel with the formation of species in nature. The 
formation and fixing of new breeds or races 
through conscious selection is exactly parallel 
with this, except that in conscious artificial selec- 



tion the destruction of the less fit is more drastic 
than in nature and the segregation of the garden 
or the flock is more perfect than is ever found in 
field or forest. There are no natural barriers so 
effective as those which may be reared in field or 

The existence of cognate or “ geminate spe¬ 
cies,” as I have elsewhere called them, the one 
representing the other on opposite sides of some 
barrier, has been long recognized by naturalists. 
In a general way such species agree with each 
other in all the respects which usually distinguish 
species within the genus. Their differences ap¬ 
pear in minor regards, characters of degree, or 
proportion; traits which we may safely suppose 
to be of more recent origin than the ordinary 
characters marking off species within the group. 

Illustrations of geminate species of birds, 
mammals, fishes, reptiles, snails, crustaceans, in¬ 
sects, trees, flowers, are well known to students 
of these groups. 

To take familiar examples, each well separated 
island in the West Indies has its own form of 
golden warbler. Each island in the East Indies 
has its own forms of reptiles, monkeys, snails, and 
fresh water fishes. Each island in Hawaii has 
its own species of each genus of Drepanine birds; 
each forest its own type of land snails. Each of 
the three groups of rookeries in Bering Sea has 
its own species of fur seal. Each section of the 
Isthmus of Panama has its geminate species of 



fishes, representing nearly every genus or sub¬ 
genus of the shore-water of Mexico. Each floral 
region of the northern hemisphere has its char¬ 
acteristic form of most of the widespread genera 
of trees or shrubs. Wherever a distinct barrier 
exists, geminate species may be found on the 
two sides of it, unless for one reason or another 
one of these forms has failed to maintain itself 
in the struggle for existence. If the barrier is 
imperfect, the two species are likely to intermin¬ 
gle, giving an intergradation of forms. The 
absence of such connecting series is the only dis¬ 
tinction between a species and a subspecies or 
geographical variety which many naturalists rec¬ 
ognize. A subspecies that lives permanently 
in the same region coincident in range with the 
species from which it springs is unknown in 


Assuming that this view of the relation of geo¬ 
graphical distribution to species-forming is a cor¬ 
rect one, it is interesting to note the attitude of 
Darwin in regard to it. 

It is clear that Darwin had the basal concep¬ 
tion of the views here set forth. His own work 
in South America and that of Wallace in the 
East Indies yielded similar conclusions, although 
with Darwin geographical studies were subordi¬ 
nated to other forms of evidence of the transfor¬ 
mation of species. Isolation Darwin considered 



mainly in its static aspects, not as a necessary or 
at least not a separate factor in evolution. 
“ Each species,” he says, “ has been produced 
within one area and has migrated as far as it 
could.” This statement may be taken as the 
central fact of our knowledge of geographical 
distribution. The distribution of each species 
covers the earth except in so far as it is unable to 
reach distant parts through barriers, or as it has 
been unable to maintain itself in regions which 
it has reached—or as it has, through selection and 
isolation, been changed in some part of its range 
into a different species. In this case as else¬ 
where selection and segregation must work to¬ 
gether, the one producing adaptive divergence or 
adaptive convergence, the other non-adaptive 
divergence alone. 

Darwin quotes from Wallace that “ every spe¬ 
cies has come into existence coincident in space 
and in time with a pre-existing closely allied spe¬ 
cies.” This coincidence is attributed, bv Darwin 
and Wallace, to “ descent with modification.” 
The language quoted is perhaps obscure, but the 
meaning of Wallace is clearly a recognition of 
the mutual relations of geminate species. 

Darwin further states: “ I do not doubt that 
isolation is of considerable importance in the for¬ 
mation of new species.” He goes on to say that: 
“ On the whole I am inclined to believe that large¬ 
ness of area is of more importance, especially in 
the production of species which will prove capa- 



ble of enduring for a long period and of spread¬ 
ing widely.” But he regards past isolation as a 
factor in this case also, for he says:— 

“ Moreover, great areas, though now continuous 
owing to oscillations of level, will often have recently 
existed in a broken condition so that the good effects 
of isolation will generally to a certain extent have 

“ In isolation in a small area, conditions will tend 
to be uniform, so that natural selection will tend to 
modify all the varying species throughout the area in 
the same manner in reference to the same conditions.” 

He goes on to show that in isolation, inter¬ 
crossing with outside individuals will be pre¬ 
vented; that individuals will be freed from outside 
competition, a condition favorable or “ giving 
time ” for “ improvement,” that is, for adaptive 

It will be noticed that Darwin uses the word 
“ isolation ” in its literal meaning of island-resi¬ 
dence, and that he does not extend it to include 
segregation or separation by barriers. Yet a 
mountain lake or a river basin may be just as 
much isolated in a biological sense for its water 
animals as an island is for its land inhabitants. 
Darwin makes no effort to separate two sets of 
facts. The one is that a great continent or a 
great sea or a great river will contain at any 
point more species than a small continent, a small 
sea, or a small river basin. This is because the 
large area offers freer access for many different 
types of organisms. Its less perfect barriers 



favor reinvasion, and each group will have some 
representatives in all available locations. The 
other fact is that the forms in the small area tend 
to be more sharply defined. They are better spe¬ 
cies, from the point of view of taxonomy, and the 
causes of their existence can be better traced. In 
our current studies of evolution, we are of neces¬ 
sity more analytical than Darwin. We would 
view as separate factors elements which to him 
were simply phases of Natural Selection. In 
artificial selection, segregation or isolation was 
taken by Darwin for granted. Natural Selec¬ 
tion was to Darwin the same cause or factor re¬ 
lated to natural processes. In his chapter on 
Geographical Distribution, Darwin shows an 
essentially modern grasp of the subject, though 
without analysis of the reasons why variations in 
distribution naturally persist. 

Darwin savs:— 

44 The preservation of favorable variations and the 
rejection of injurious variations, I call Natural Selec¬ 
tion. Variations neither useful nor injurious would be 
unaffected by natural selection, and would be left a 
fluctuating element.” 

It is clear that the completed process of Nat¬ 
ural Selection as here indicated implies segrega¬ 
tion also, especially if we are to explain how those 
forms bearing “ fluctuating elements ” are to be 
coordinated as species. It is, moreover, certain 
that in most groups, probably in all, the charac¬ 
ters that distinguish species are these elements, 



neither useful nor injurious. Unless we use 
“ Natural Selection ” to cover both processes, as 
Darwin certainly would have done, we must as¬ 
sign to selection the preservation and intensifi¬ 
cation of adaptive characters, and to segregation 
the seizing and fixing of the non-useful, usually 
fluctuating, element. It is, however, a fact well 
known to breeders that these indifferent or non¬ 
useful characters are often or generally more per¬ 
sistent in heredity than the traits which are 
plainly adaptive. The slight traits which mark the 
races of men are in themselves, often not ob¬ 
viously, valuable in the struggle for existence. 
They are mostly ineradicable in such selective 
breeding as history offers. In like manner the 
dusky face, and other marks of Hampshire sheep, 
persist after the adaptive traits of the original 

modified by selection 
in the direction we regard as sheep improvement. 
But fine or coarse, fat or lean, Hampshire sheep 
are still Hampshires. 

In Darwin’s view, isolation or segregation was 
doubtless a feature of Natural Selection, not to 
be set off against the latter as a separate factor 
in descent. It is very plain from Darwin’s own 
words, as well as from the explicit statement of 
Francis Darwin, that his main contention was for 
the reasonableness of the idea of the origin of spe¬ 
cies through descent with modification. What 

breed have been enormously 

were the causes of modification, was to him a sec¬ 
ondary matter. But he was convinced of the 



existence of one such cause, and this one he set 
forth in most effective fashion. Without selec¬ 
tion, the other life-forces known in his day could 
not be imagined to lead to any evolutionary re¬ 
sults. We are to-day in the same condition. If 
we exclude selection from our category of forces, 
we imagine an evolution without motive force, an 
evolution which would bring about no result. 
But in Darwin’s mind, Natural Selection was the 
cognate of artificial selection. At bottom they 
were to him the same thing, and segregation a 
necessary element in both. 

Natural Selection was contrasted to supernat¬ 
ural selection or special creation, a theory by 
which knowable facts were referred to unknow¬ 
able causes, operations wholly unimaginable in 
application to details. At present, we have 
ceased to set off selection as against creation. 
We agree that all processes are alike natural or 
alike supernatural, if we consider them in their 
philosophic aspects. 

The origin of a species is as natural as the for¬ 
mation of a snow bank, and both are resultants of 
forces and conditions within the range of our ob¬ 
jective study. 


As compared with Darwin, the investigator of 
to-day has more facts at his disposal; better in¬ 
struments of precision; less need to heed the 
opposition of ignorance and bigotry; and greater 



need for analysis of scientific conceptions. Under 
these conditions, while not departing in essentials 
from the position of Darwin, we are forced to 
bring forward isolation as one of the separate 
factors in the origin of species, and the factor on 
which the great and growing science of animal 
and plant geography mainly depends. 

Nearly a decade after the publication of the 
Origin of Species 3 Dr. Moritz Wagner set forth 
the factor of isolation, and showed in convincing 
fashion its fundamental relation to the problem 
of the origin of species. 

Wagner showed plainly that in the study of 
the evolution of any form we need to know where 
it lived, what it did, how it was bounded, and 
what was its relation to other forms, geographic¬ 
ally as w r ell as morphologically. “ For me,” he 
says, “ it is the chorology of organisms, the study 
of all the important phenomena embraced in the 
geography of animals and plants, which is the 
surest guide to the knowledge of the real phases 
in the process of the formation of species.” 

The work of Wagner, a most necessary sup¬ 
plement to that of Darwin, has never received the 
attention it deserves. This is due in part to the 
fact that most of our investigators do not travel. 
They know little of animal or plant geography at 
first hand. They have had nothing to do with 
species as living, varying, reproducing, adapting, 
and spreading groups of organisms. Another 
reason lies in Wagner’s own attitude of opposi- 



tion to Darwinism. He substituted separation, 
“ raiimliche Sonderung,” for Natural Selection 
itself, and denied the potency of the latter factor. 
The two became in his philosophy competing, not 
cooperating, elements, and this threw on isolation 
the impossible task of accounting for all the phe¬ 
nomena of adaptation. We may not ascribe 
to Natural Selection the “ Allmacht,” or limit¬ 
less power, which some Neo-Darwinians have 
ascribed to it, but on the other hand, those who 
reject it as a factor in organic evolution can 
give no rational explanation of the universality 
of adaptive organs and adaptive traits; no clue 
to the most universal characters of organic nature 
as it is. 

Certain writers urge that neither selection 
nor isolation are factors in evolution, hut rather 
elements in speciation or species-forming, a proc¬ 
ess defined as something distinct from evolution. 
Selection and isolation, as obstacles in the stream 
of life, help to split the on-moving group of or¬ 
ganisms into different categories or species; but 
the impulse of the forward movement is internal, 
and the changes of evolution proper affect groups 
as a whole, and are not concerned with splitting 
them up into species. 

This view may be questioned in two ways. It 
may be untrue as to fact, or it may be a matter 
of words only. As a matter of fact, we know 
nothing of evolution in vacuo , of progress in life 
without relation to environment. All forms of 



life, we know, are split up into species, with 
adaptation to external conditions traceable in 
every structure. We know of no way in which 
organisms can become adapted to special condi¬ 
tions except by the progressive failures of those 
not adaptable. Hence we know of no organism 
which has escaped or can escape from the influ¬ 
ence of selection. In like manner, as the world 
is covered with physical barriers, no organism 
can escape the form of evolutionary friction 
which prevents uniformity in breeding. There 
must be some degree of “ raumliche Sonderung,” 
even in a drop of water. 

To admit these facts, and yet to say that selec¬ 
tion and isolation are not factors in evolution, 
w r ould appear to make the matter a mere question 
of words. If by evolution we mean the theoret¬ 
ical progress of life, in vacuo, the effects solely 
of forces intrinsic in organisms, then extrinsic 
forces or extrinsic obstacles are of course not fac¬ 
tors in such evolution. If we mean by evolution, 
the actual life movements of actual organisms, on 
this actual earth, then forces and obstacles are 
alike factors in modifying change, and both spe- 
ciation and adaptation as well necessary parts of 
the process. 

We admit the primary necessity of variation 
and of heredity, but we can conceive of no case 
of actual animal or plant in the forming of which 
selection and isolation have not played each a 
large and persistent part. Among the factors 



everywhere and inevitably connected with the 
course of descent of any species, variation; hered¬ 
ity, selection, and isolation must appear; the first 
two innate, part of the definition of organic life, 
the last two extrinsic, arising from the necessities 
of environment, and not one of these can find 
leverage without the presence of each of the 
others. Isolation as the factor longest over¬ 
looked, though to the field naturalist the most 
conspicuous of the four, must be advanced to the 
post of honor beside the others, not instead of 
any of them. 




I trust that my colleagues in this symposium 
will not suspect me of any intention disrespectful 
to them if I speak of my own small contribution 
to it as the voice of one crying in the wilderness. 
I do not mean to imply by the Scriptural phrase 
that the cytologist has to announce the coming of 
a new gospel of heredity or of evolution. He is, 
to say the least, as much in need of light as are 
others. I wish only to suggest the somewhat iso¬ 
lated position of the subject assigned to me, deal¬ 
ing, as it mainly must, with matters with which 
Darwin’s own work was not very directly con¬ 
cerned, and which in their detailed aspects belong 
mainly to the post-Darwinian period. With the 
notable exception of the provisional hypothesis 
of pangenesis Darwin made no systematic at¬ 
tempt to correlate his own conclusions with those 
towards which cell-research was already tending 
in his day; and pangenesis was rather a specula¬ 
tive construction than an induction from known 
cytological facts. Nevertheless my intrusion 
into this circle may perhaps be justified on two 
grounds. One is the keen interest in the inter- 




nal mechanism of heredity everywhere shown by 
Darwin in his remarkable chapter on pangenesis 
and attested by many passages in his private let¬ 
ters. The other is the now general admission 
that the mechanism over which Darwin so long 
pondered is to be sought in the organization of 
the germ-cells. 


Of the original hypothesis of pangenesis I shall 
say but a few words. Darwin says in one of his 
letters that he had considered it for upwards of 
five-and-twenty years. It is easily the most ab¬ 
stract and speculative portion of all his writings. 
It was published against the advice of his trusted 
friend and counselor, Huxley, who had himself 
many years earlier written one of the first and 
ablest reviews of the cell-theory that appeared in 
our language. Darwin predicted that pangene¬ 
sis would be called a mad dream; and on its pub¬ 
lication the hypothesis was, in fact, received for 
the most part with hostile criticism or scanty ap¬ 
preciation. In its original form it has been gen¬ 
erally abandoned; though one of its principal 
postulates, remodeled by De Vries to form the 
hypothesis of “ intracellular pangenesis,” is still 
accepted by some biological thinkers. It is none 
the less deeply significant that so great and saga¬ 
cious a naturalist, one whose life was so largely 
given to the study of the external aspects of 



heredity and evolution, should have found him¬ 
self irresistibly driven to look below the surface 
of these phenomena and should have made so 
carefully wrought an attempt to picture their 
physical foundations to his mental vision. His 
deep-seated conviction that sooner or later the 
phenomena would have to be attacked from this 
side is revealed in a letter written to Sir Joseph 
Hooker, in 1868, where he declares, “ I feel sure 
that if pangenesis is stillborn it will, thank God, 
at some future time reappear, begotten by some 
other father and christened by some other name.” 
That this prediction still awaits fulfilment need 
not here concern us. What is significant is the 
attitude towards the general problem that it re¬ 
veals. And the modern cytologist, therefore, de¬ 
spite his failure to find support for Darwin’s par¬ 
ticular conception, has a right to feel that his 
efforts to analyze the cellular mechanism of 
heredity would be viewed with sympathetic inter¬ 
est by the great naturalist could he follow their 
progress at the present time. 

Pangenesis was put forward many years after 
Virchow had pronounced his celebrated apho¬ 
rism Omnis cellula e cellula ” (which Darwin 
quotes), and a full decade after the eminent Ger¬ 
man pathologist had insisted on the “ eternal 
law ” of genetic continuity by cell-division. Dar¬ 
win nevertheless admitted this law unreservedly 
only in the case of plants, and went no further 
than to recognize its wide prevalence among ani- 



mals. In both cases he assumed that in addition 
to the powers of division cells multiply by means 
of minute germs or “ gemmules,” which are 
thrown off by the somatic cells, collected from all 
parts of the body to form the sexual elements, and 
are “ ultimately developed into units ” (cells) 
like those from which they were originally de¬ 
rived. 1 Pangenesis thus comprised two princi¬ 
pal postulates, both of which had been in a meas¬ 
ure foreshadowed by the speculations of Bonnet, 
Buffon, and even earlier writers. One is the 
particulate or meristic assumption that particular 
hereditary traits are represented in the germ-cell 
by discrete and specifically organized particles, 
the “ gemmules ” or “ pangens,” that are capable 
of self-perpetuation by growth and division with¬ 
out loss of their specific character. The second 
assumption is that the gemmules are cell-germs 
originally produced by the somatic cells; and by 
this Darwin sought to explain the transmission 
of somatogenic or acquired characters. How 
have these two assumptions fared with the prog¬ 
ress of modern studies on the cells? 

1 The development of the gemmules was supposed to depend on 
their “ union with other partially developed or nascent cells, which 
precede them in the regular course of growth.” Darwin does 
not make it quite clear whether he assumed that the gemmules 
actually grow into new cells. Many passages (like the one placed 
in quotation marks in the text above) seem open to no other 
interpretation; but in the case of plants, accepting the universality 
of division in them, he concluded that “ the gemmules derived 
from the foreign pollen do not become developed into new and 
separate cells, but penetrate and modify the nascent cells of 
the mother plant.” This process, he says, is almost identical with 
a fertilization of the ceils of the mother plant by gemmules 
derived from the foreign pollen. 



The first has been accepted by many acute bio¬ 
logical thinkers as almost a logical necessity, and 
has been developed, especially by Weismann, into 
one of the most ingenious and elaborate specula¬ 
tive constructions to be found in the whole his¬ 
tory of biology. Its logical grounds need not 
here be analyzed. I will only emphasize the fact 
that the conception did not grow out of actual 
studies on the cell, but was an imaginative con¬ 
struction, based on the facts of variation and 
heredity. It may be true; but for the present we 
can only regard it as a kind of symbolism, anal¬ 
ogous in some respects to the molecular-atomic 
symbolism of physical science, hut of far more 
doubtful validity. Those who find such a sym¬ 
bolism useful will encounter no positive obstacle 
in the known cytological facts—they may even 
find in them a certain amount of indirect support 
—but the assumption remains unverified, and is 
probably unverifiable. 

The second postulate of pangenesis is wholly 
unsupported by either experimental or cytolog¬ 
ical evidence. There is not a particle of evidence 
to show that in the higher forms of life cells pro¬ 
duce gemmules or that the germ-cells are built 
up by the aggregation of such bodies derived 
from the somatic cells. The most fundamental 
contribution of cell-research to the theory of he¬ 
redity is the law of genetic continuity by cell- 
division. Cells arise only by the division of pre¬ 
existing cells. And the stream of growth and 



division by which the continuity of organization 
is maintained seems clearly enough to be genetic¬ 
ally irreversible. It flows forward from germ¬ 
cell to germ-cell in endless succession. It is peri¬ 
odically diverted from the germ-stream to form 
the bodies of successive generations of individ¬ 
uals. These are made of the same stuff as the 
stream from which they flow. In each genera¬ 
tion the germinal stuff runs through the same 
series of transformations; hence that reappear¬ 
ance of the same traits in successive generations 
that we call heredity. 

This conclusion loses nothing of its force by 
reason of the fact that in a sexual reproduction 
or regeneration the whole body may be repro¬ 
duced from a fragment, from a small group of 
cells, or even from a single cell, of the soma. 
These cells, too, have arisen by division in un¬ 
broken descent from the germ-cell; they, too, 
have been made from the same original stuff; and 
they, too, hand on by division to their descendants 
the specific tradition of their lineage. It is true 
that these cells and the germ-cells alike grow by 
the intussusception of matter from without, that 
the cell-substance is built from, and its activities 
modified and controlled by, materials that have 
been elaborated by other cells. But the whole 
force of the evidence goes to show that their fun¬ 
damental basis is determined by genetic contin¬ 
uity with that of their predecessors, that some¬ 
thing is handed on by division which holds 



the cell true to its specific type and builds the 
incoming food-stuff s into the characteristic fabric 
of the species. I need not dwell on a conception 
with which we are all so familiar. Some of the 
specific applications of the doctrine may have 
proved unacceptable, but the advances in our 
knowledge of the cell are ever adding weight to 
the fundamental principle of germinal continuity 
for which so many eminent investigators, from 
Remak and Virchow to Nussbaum and Weis- 
mann, have contended. And this principle ob¬ 
viously affords the true standpoint from which 
the phenomena of heredity and development 
must be viewed. 

From this standpoint we are confronted with 
four principal questions, which I shall in the 
briefest possible way attempt to consider. (1) 
What is the physical basis of heredity? (2) How 
is it transmitted from cell to cell? (3) In what 
way does it play its part in the determination of 
the hereditary characters? (4) How may it be 
so modified as to give rise to new heritable char¬ 
acters ? 


It is now universally admitted that the physical 
basis of heredity is contained in the germ-cell. 
Is this basis formed by the entire living energid, 
or may we distinguish in the cell a particular 
species-substance or idioplasm, that is at least 
theoretically separable from the other cell-con- 



stituents? This question has not yet been an¬ 
swered with certainty. The cell-system forms 
an enormously complex moving equilibrium, 
which must in one way he regarded as a single 
and indivisible unit. From this point of view it 
may justly be maintained that the basis of hered¬ 
ity and of the vital activities generally is repre¬ 
sented by the cell-system in its totality. But 
such a position, philosophically correct though it 
may be, cuts us off from the possibilities of exact 
analysis. We have every right to inquire in what 
way the energies of cell-life are distributed in the 
system and how they are related; and the ques¬ 
tion whether certain elements of the system may 
possess an especial and primary significance for 
the determination of the cell-activities forms a 
legitimate part of this inquiry. 

I stand with those who have followed Oscar 
Hertwig and Strasburger in assigning a special 
significance to the nucleus in heredity, and who 
have recognized in the chromatin a substance that 
may in a certain sense be regarded as the idio¬ 
plasm. This view is based upon no single or 
demonstrative proof. It rests upon circumstan¬ 
tial and cumulative evidence, derived from many 
sources. The irresistible appeal which it makes 
to the mind results from the manner in which it 
brings together under one point of view a multi¬ 
tude of facts that otherwise remain disconnected 
and unintelligible. What arrests the attention 
when the facts are broadly viewed is the unmis- 



takable parallel between the course of heredity 
and the history of the chromatin-substance in the 
whole cycle of its transformation. In respect to 
some of the most important phenomena of hered¬ 
ity it is only in the chromatin that such a par¬ 
allel can be accurately traced. It is this sub¬ 
stance, in the form of chromosomes, that shows 
the association of exactly equivalent maternal 
and paternal elements in the fertilization of the 
egg. In it alone do we clearly see the equal dis¬ 
tribution of these elements to every part of the 
body of the offspring. In the perverted forms 
of development that result from double fertili¬ 
zation of the egg and the like it is only in the 
abnormal distribution of the chromatin-substance 
by multipolar division that we see a physical coun¬ 
terpart of the derangement of development. 
Only in the chromatin-substance, again, do we 
see in the course of the maturation of the germ- 
cells a redistribution of elements that shows a 
parallel to the astonishing disjunction and redis¬ 
tribution of the factors of heredity that are dis¬ 
played in the Mendelian phenomenon. 

These are perhaps the most striking of a mul¬ 
titude of facts that point towards the chromatin 
as the embodiment of specific primordia of deter¬ 
mination. We may he sure that the microscope 
reveals to us but part of the story; but that which 
we see is not for this reason less significant. Ex¬ 
periment has taught us, it is true, that the role of 
the nucleus in determination cannot be regarded 



as an exclusive one. It is certain that specific 
factors of determination also exist in the proto¬ 
plasm of the egg; it is possible that the same may 
be true of the spermatozoon. Experiment has 
demonstrated in the clearest manner that many 
features of the early development, among them 
some of the most important, are immediately de¬ 
termined by conditions in the egg-protoplasm 
without direct action of the nucleus. But this 
fact can be rightly estimated only when the whole 
genesis of the egg has been taken into account. 
The researches of recent years have proved that 
the egg undergoes a long process of development 
during its ovarian history and in the process of 
maturation, in the course of which the greater 
part of its protoplasmic substances are formed 
and ultimately segregated in a particular config¬ 
uration. It has thus become more than probable 
that some at least of the determinative conditions 
in the protoplasm of the fertilized egg are of sec¬ 
ondary origin—that they are the outcome of an 
antecedent development in which the nucleus has 
played its part. Important formative protoplas¬ 
mic materials are known to be of nuclear origin. 
It is possible that all may have such an origin. 
But even if we do not go so far as this, even if we 
admit that the determinative factors of the nu¬ 
cleus constitute but one element in an activity 
that properly belongs to the living energid as a 
whole, we still can not close our eyes to the plain 
record that is written in the history of the nuclear 



substance. I doubt whether any one holds the 
view, which some of the opponents of the chro¬ 
matin hypothesis have endeavored to force upon 
its adherents, that the nucleus enjoys a complete 
“ monopoly of heredity.” To what extent the 
chromatin embodies primary factors of deter¬ 
mination remains to be shown hv further re¬ 
search. We are still too ignorant of the physio¬ 
logical relations of the nucleus and cytoplasm to 
be justified in any attitude of dogmatism on this 
question. But as a matter of evidence the con¬ 
clusion that chromatin does embody such factors 
seems at least a probable one. As a means of 
practical inquiry it is, I believe, a good working 
hypothesis, without which we should be deprived 
of one of our most effective instruments for the 
analysis of the mechanism of heredity. And re¬ 
cent research has, I think, clearly shown that, far 
from being exhausted as some of its critics would 
have us believe, this hypothesis is steadily open¬ 
ing new possibilities of inquiry. 


Accepting the idioplasm hypothesis, in the 
sense I have indicated, what do we know of its 
mode of transmission? We mav answer with 
assurance that it is transmitted from cell to cell 
by division; and we may still safely assume, I 
think, in most cases by mitotic or karyokinetic 
division, though the direct or amitotic process may 
play a larger role than was formerly supposed. 



We can but glance at one or two of the most 
significant features of karyokinetic division. The 
most striking and telling of these is the contrast 
so often shown between the distribution of the 
nuclear and of the protoplasmic elements. With 
certain exceptions in the phenomena of matura¬ 
tion, which only bring fresh support to the general 
principle, nuclear division is both quantitatively 
and qualitatively exactly equal. Protoplasmic 
division is often both quantitatively and qualita¬ 
tively unequal, separating substances that have 
been proved by precise experiment to be of dif¬ 
ferent physiological value. But more than this, 
the formation and division of chromosomes effect 
not merely a mass-division of the chromatin but 
an equal meristic division of its whole substance; 
and as Wilhelm Roux first urged, we can find no 
meaning in the whole elaborate process if the 
chromatin be not composed of qualitatively dif¬ 
ferent elements that require equality of distribu¬ 
tion. That such is really the constitution of the 
chromatin can no longer be doubted by any who 
are familiar with the evidence. If the chromo¬ 
somes be not actually persistent individuals, as 
Rabl and Boveri have maintained, they must at 
least be regarded as genetic homologues that are 
connected by some definite bond of individual 
continuity from generation to generation of 
cells. And the evidence has steadily accumulated 
to show that the chromosomes exhibit definite 
qualitative differences. In many animals and 



plants constant differences of size, in some cases 
also of form, are shown among the chromosomes. 
Specifically different classes of chromosomes can 
in some cases be distinguished, which show con¬ 
stant and characteristic peculiarities of behavior 
in respect to some of the most important opera¬ 
tions of the cell. The probability is increasing 
that individual chromosomes possess a particu¬ 
lar significance for the development of particular 
characters. It has become probable that sexual 
dimorphism in general is determined by a differ¬ 
ence of nuclear constitution between the sexes. 
In some groups of animals the sexes differ in 
respect to one or more particular chromosomes. 
In a more general way, Boveri’s experiments 
have proved that abnormal combinations of chro¬ 
mosomes lead to falsified forms of development; 
and these observations give the strongest reason 
to believe that normal development is dependent 
upon the normal combination of the chromo¬ 

All these facts are pointing in the same direc¬ 
tion. They render the conclusion almost irre- 
sistible, not only that the chromatin-substance is 
involved in heredity, but that the chromosomes 
are composed of specifically different materials, 
the ensemble of which is essential to normal devel¬ 
opment. It is obvious that the beautiful mechan¬ 
ism of karyokinesis is perfectly adapted for the 
meristic division and equal distribution of these 
materials. The energies that lie behind the for- 



mation and action of the karyokinetic figure con¬ 
stitute a puzzle for which, as it seems to me, no 
adequate solution has yet been found. But the 
effect of its action gives us good reason to regard 
it as the most important instrument by which the 
nuclear substance is handed on with its integrity 
unimpaired from generation to generation of 


Our third question involves the problem of dif¬ 
ferentiation, which is inseparable from that of 
cell-metabolism in general, since it involves the 
mode of interaction of nucleus and protoplasm. 
It is a significant fact that visible structural dif¬ 
ferentiation affects the protoplasmic substance in 
far greater degree than the nuclear. Both in 
their structure and in their modes of activity the 
most important characteristics of different kinds 
of cells are found in the protoplasm. To some 
extent, no doubt, the nuclei of different tissues 
show certain characteristic peculiarities, and these 
can in a measure be correlated with the function 
of the cells. It is nevertheless obvious that the 
most characteristic features of the muscle-cell, 
the nerve-cell, or the gland-cell are displayed in 
the protoplasmic rather than the nuclear sub¬ 
stances. And this again falls into line with the 
view that the nucleus is the main conservative 
element of the cell-system, the protoplasm the 
plastic element through the modifications of 



which the cell adapts itself to the performance of 
the varied special conditions of cell-life. 

In considering the problem of differentiation 
we are therefore led to inquire in what manner 
the nucleus may be conceived to operate in the 
determination of specific modes of protoplasmic 
change. De Vries and many of his followers 
have supposed that control of the cell is effected 
by an actual migration of organized gemmules or 
pangens from nucleus to protoplasm. But do 
we really need to employ the pangen symbolism 
in the consideration of this question? It seems a 
sufficient basis for our practical attack on the 
problem to assume that the control of the cell- 
activities is at bottom a chemical one and is 
effected by soluble substances that may pass from 
nucleus to protoplasm or from protoplasm to 
nucleus. Certainly it is to such a view that very 
many of the chemical and physiological studies 
in this field are now unmistakably pointing. The 
opinion is gaining ground that the control of de¬ 
velopment is fundamentally analogous, perhaps 
closely similar, to the control of specific forms of 
physiological action by soluble ferments or en¬ 
zymes. Experiment has established the fact that 
certain forms of development are thus controlled 
by substances, the “ hormones,” that may be ex¬ 
tracted from the cells that produce them, and 
upon injection into the body call forth their char¬ 
acteristic results. Such an effect, for instance, 
is the development of the cock’s comb in the hen 



upon injection of testic-extract and its recession 
to the characteristic female condition upon cessa¬ 
tion of the injections, as recently described by 
Walker. Analogous phenomena are seen in the 
well-known effects of thyroid extracts, or in the 
effect upon the mammary glands of injection of 
extracts of the fetus, as described by Starling 
and Lane-Claypole. 

We are thus led to something more than a sus¬ 
picion that the factors of determination, and 
therefore of heredity, are at bottom of chemical 
nature. It is a well-known fact that correspond¬ 
ing tissues of different species often show char¬ 
acteristic chemical differences; and to some extent 
the same is known to be true of the germ-cells. 
The conclusion thus becomes highly probable that 
the characteristic differences of metabolism be¬ 
tween different species, including those involved 
in development, are traceable to initial chemical 
differences in the germ-cells. In so far as the 
chromatin theory expresses the truth, the pri¬ 
mary basis of these differences may he sought 
in the nuclear substance. There is good reason 
to believe that some at least of the enzymes are 
of nuclear origin. It seems a promising hypoth¬ 
esis that the chromosomes may be regarded as 
self-perpetuating magazines of specific sub¬ 
stances, similar in nature to the enzymes or their 
chemical antecedents, that play an essential role 
in the determination of the cell-activities, includ¬ 
ing those involved in development. From this 



point of view the fertilization of the egg might 
almost be compared to an intracellular injection 
of enzymes. 

The apparent simplicity of such an hypothesis 
should not delude us into the belief that it touches 
the root of the matter. It presupposes a specific 
“ organization ” of the chromosomes of which we 
know nothing, and upon which must depend the 
perpetuation of their characteristic chemical con¬ 
stituents. In this direction we are thrown back 
upon purely speculative constructions which it 
would be unprofitable to follow out here. But 
so far as the hypothesis goes it seems to offer a 
really practical point of attack for the chemical 
study of differentiation and heredity. In the 
Mendelian phenomenon we see a synthesis, split¬ 
ting apart, and recombination of determinative 
factors that is singularly like that of chemical ele¬ 
ments or radicals. In the Mendelian hereditv 
of color, for instance, the orderly resolution by 
the germ-cells of compound pigment-producing 
factors into simpler ones, their recombination to 
form new compounds, the intensification or dilu¬ 
tion of color by specific and separable factors, the 
production of particular colors by mixing to¬ 
gether factors which are singly incapable of pro¬ 
ducing color—in all this we see a series of oper¬ 
ations that show an astonishing similarity to the 
procedure of the chemist in his laboratory. That 
such things are possible in the case of relatively 
simple characters, such as colors, gives strong 



ground for the belief that similar operations are 
concerned in the production of more complex 
characters. Those who hesitate to draw such a 
conclusion may well reflect upon the remarkable 
effects of the “ internal secretions ” of the en¬ 
zymes and hormones, and upon the extreme sus¬ 
ceptibility of the developing embryo to even very 
slight chemical changes in the surrounding me¬ 
dium. It is my belief that in the direction here 
indicated lie the greatest possibilities of future 
investigations upon the cell, and that in the union 
of cytology and biochemistry lies our greatest 
hope of future advance. 


Lastly, if we accept the working hypothesis 
that the primordia of determination are chemical 
in nature, how may we conceive them to be so 
modified as to produce new characters ? It seems 
to me that this question may well be reversed; for 
the wonder is, not that the idioplasm changes, but 
that it adheres so stubbornly to its type. It may 
as well be admitted that both our cytological and 
our chemical knowledge in this direction is prac¬ 
tically nil. It is well, further, to speak a word 
of caution at this point. We must not forget 
that some of the most acute and thoughtful of 
naturalists have in recent years expressed the 
conviction that the ultimate control of develop¬ 
ment is not to be sought in the physico-chemical 
properties of the germ-cells, but in an indwelling 



“ entelechy ” or “ elan de la vie,” a power of un¬ 
known nature, that may, in the last analysis, be 
psychical in nature. But, profoundly interest¬ 
ing as some of these vitalistic speculations are, we 
are bound to hold fast to the physico-chemical and 
mechanistic hypothesis of heredity until the pos¬ 
sibilities of observation and experiment in this 
direction have been exhausted. If there be a 
physico-chemical basis of heredity we should ex¬ 
pect to find it capable of modification by physico¬ 
chemical agencies; and so much, at least, is known 
to be the fact. It has been abundantly demon¬ 
strated that both the body-cells and the germ- 
cells react to changes of the environment by def¬ 
inite physiological and morphological changes. 
Many experimenters have demonstrated the ex¬ 
treme susceptibility of the discharged eggs or 
spermatozoa to even very slight chemical and 
physical stimuli. We can not doubt that they are 
equally sensitive to stimuli while still within the 
body, and at every stage of their development. 
The almost unique experiments of MacDougal 
on the higher plants seem to show that direct 
chemical treatment of the germ-cells may pro¬ 
duce definite and irreversible effects upon the off¬ 
spring. Those of Tower on the insects, though 
less direct, are hardly less convincing. 

Though we may not fully understand the man¬ 
ner in which the germ-cells are modified, there is 
no inherent improbability or difficulty in the con¬ 
ception that such modifications will produce bias- 



togenic variations or mutations that are inherited, 
permanently or temporarily. We can readily 
understand that the constitutional effects of tem¬ 
perature, food, moisture, and similar general 
agencies of the environment may manifest them¬ 
selves in definite changes that reappear in follow¬ 
ing generations because the germ-cells have been 
directly affected in the same way as the somatic 
cells. It is natural to suppose that the idioplasm 
possesses a slight instability of chemical or molec¬ 
ular composition that results in corresponding 
fluctuations or indefinite variations of the adult, 
which may or may not be inherited. We find no 
difficulty in the conception that the idioplasm 
may undergo considerable, sudden, and irre¬ 
versible changes which produce mutations of 
greater or less degree. We can comprehend how 
particular constituents of the idioplasm may 
change without affecting others, thus giving rise 
to mutations in respect to only a single character 
or a particular group of characters. We can con¬ 
ceive the idioplasm as undergoing a slow secular 
change that results in continual divergence in 
many directions or in a definite orthogenetic line 
of transformation. But in respect to the trans¬ 
mission of acquired characters the old difficulty 
confronts us to-day as formidable as when it was 
first fairly revealed to us through the argument 
of Weismann. What is really difficult to com¬ 
prehend, what I think we can not really conceive 
if pangenesis be discarded, is how the idioplasm, 



or the germ-cell as a whole, can be a storehouse of 
specific and detailed somatic impressions which 
cause the reappearance of similar somatic effects 
in generations to come. 

Darwin’s ingenious attempt to picture such a 
process was a legitimate speculation, worked out 
with a power and insight that should stir enthu¬ 
siasm in even the most skeptical of critics. More 
than this, it still remains, as I think, the only in¬ 
telligible hypothesis of the transmission of ac¬ 
quired characters, as Darwin understood the 
phrase. But it finds to-day little or no real sup¬ 
port in the results of observation and experiment. 
Attempts have been made to substitute for Dar¬ 
win’s migrating gemmules soluble internal secre¬ 
tions—hormones or other substances—that are 
produced by the various organs and transmitted 
to the reproductive organs through the fluids of 
the body. Heredity has been compared, and 
with justice, to an “ organic memory and this 
has been assumed to he a property of the organ¬ 
ism as a whole, irrespective of the distinction be¬ 
tween germ-cells and soma. It has been urged 
that the heredity of acquired characters is more 
readily conceivable if the increments of change 
be small and extended through long periods of 
time. Any or all of these tilings are possible; 
but let us not deceive ourselves. Does any of 
these assumptions really lessen the difficulty or 
give us a clear mental picture of what must occur 
if the heredity of acquired characters be a fact? 



I do not see how. Inability to form a clear 
a priori conception of the process has in itself no 
validity as an argument against the fact, if fact 
it be. The progress of biological discovery has 
repeatedly transformed apparent a priori impos¬ 
sibilities into everyday realities. And if exper¬ 
iment shall really demonstrate the transmission 
of somatogenic modifications the cytologist has 
no fundamental obstacle to interpose. The 
mechanism that his studies have revealed will ac¬ 
count for the transmission of all forms of ger¬ 
minal modifications, however they may be caused. 
The question involved is not of the transmission 
of the idioplasm or of the germ-cell, but of its 
interaction with the soma; and this is not an 
a priori question, but one of fact. Let us admit 
freely that such an interaction as Darwin as¬ 
sumed may be a real and potent factor in hered¬ 
ity, though it gives no hint of its existence in the 
visible apparatus of the cell. In the present 
defective state of our knowledge we may well 
grant that there may be many a thing between 
germ-cell and body that is not yet dreamed of in 
our biological philosophy. But has the trans¬ 
mission of acquired characters, in the strict and 
proper sense of that much abused phrase, been 
demonstrated? If in closing I venture to ques¬ 
tion this, I pray that my sins be not visited upon 
the study of the cells, but upon a failure to dis¬ 
cover the demonstration in other fields of inquiry. 




Any serious consideration of the diversity of 


organisms, of the complexity of the qualities they 
bear, of the relationships they sustain, and of the 
character of the stresses under which they exist 
with relation to the environmental setting, leads 
inevitably to the conclusion that their evolution¬ 
ary development must have been affected by 
many modifying agencies; that the origination, 
or activation of their qualities or characters may 
not be ascribed to any single causal force or guid¬ 
ing factor; and that the course of heredity from 
generation to generation has been determined 
by many tilings beside the simple inertia of prim¬ 
itive initial qualities of protoplasm. 

When we join in the accepted generalization 
that the qualities and forms of organisms now 
existent are the net result of the action of envi- 
ronic forces upon ancestral structures, selective 
as well as initiatory, we implicate a much larger 
group of conceptions than that embodied in the 
present thesis, since it is the intention to confine 
discussion to the possibilities that arise when liv- 



ing or self-generating matter transmits its spe¬ 
cialized characters from one generation to an¬ 
other in the germ-cell, and displays its periodic 
somatic expansions in ontogeny. 

Within this definite and restricted field, exact¬ 
ness and clearness of comprehension of the rela¬ 
tions involved will depend directly upon the thor¬ 
oughness with which we may be able to connect 
our conceptions with the physico-chemical proc¬ 
esses of organisms. 

The more important external, direct, or phys¬ 
ical factors, the influence of which induces adjust¬ 
ments and engages the activities of protoplasm, 
include radiant energy in its various phases, and 
the chemical structure of the medium, substratum 
or substances coming into contact with the living 
matter and included with its intake and output. 
These agents interlock intimately with the parts 
of the self-generating protoplasmic machine, fur¬ 
nishing building material, energy in various 
forms, catalysts, and control reactions in a man¬ 
ner so intimate that it is impossible to think of 
living matter free from its environic setting. 

Now if we set about the calibration of the quan¬ 
titative relation of any of these factors to living 
matter, or attempt an estimation of the qualita¬ 
tive effect, we will find that, with respect to any 
given strain of organisms or any individual, the 
constellation of specific activities, processes or 
functions, grouped in the plant are adjusted in 
such manner that they proceed at the most advan- 



tageous rate with relation to each other within, 
for example, some narrow range of temperature. 
In our easy acceptance of the obvious, we are apt 
to assume that these optimal conditions are fur¬ 
nished by the native habitats of plants, or in other 
words, the place they happen to occupy in their 
movements about the world when they are called 
to our attention. Now, on the one hand, plants 
simply are found in areas they have been able to 
reach, and “ native habitats ” may by no means 
offer the optimal conditions, a condition of affairs 
of which more than a hint is furnished bv the 
irruption of weeds, followed by a development 
of a vigor unknown within the previous range of 
the species. On the other, the reminder is neces¬ 
sary that no one habitat may furnish the optima 
for the accomplishment of all of the processes 
involved in the ontogeny and reproduction of the 
individual, and all environic relations include 
groups of compromises and of adjustments that 
put the capacity of the living matter to the ut¬ 
most stresses it may hear. 

Two main considerations arise when attention 
is directed to the behavior of the organism as it 
encounters the external factors in unusual inten¬ 
sities, an experience which has been countlessly 
repeated and which is one of the eliminating fac¬ 
tors in selection. The first concerns the mechan¬ 
ism of the adjustment of the individual to alter¬ 
ing environment, and the second, the possibilities 
of transmission of the effects of the adjustment 



to the progeny, both in functional capacity and 
accompanying structure. 


Let us take, for example, a plant standing in 
the open in a habitat in which it is firmly estab¬ 
lished, and introduce some modifications of wide 
range of the insolation, which may or may not 
register with anything previously encountered by 
this individual. The primary or direct effect of 
the change will undoubtedly be a modification of 
the reaction-velocities of some of the chemical 
processes so that metabolism and all of the life- 
phenomena dependent upon it will undergo alter¬ 
ations in rate, cell-division, chromosomatic invo¬ 
lution, catalyptic action involving respiration, 
intake and excretion, and finally growth also. 
A secondary effect accompanying these changes 
will be due to the irritability of the living matter 
by which sudden changes in almost any external 
factor will exercise a releasing or unloosing ac¬ 
tion. Outward manifestations of such action are 
seen in the various thermotropic and heliotropic 
movement of leaves, and while there seems to be 
a disposition on the part of some physiologists to 
eliminate metabolic activities from the realm of 
irritable reactions, yet it does not seem justifiable 
upon present evidence. 

Whether an irritational phase intervenes or 
not, when an environmental factor undergoes 



rapid alteration, the activities affected soon as¬ 
sume a fairly steady rate, determined directly by 
the reaction velocities of the substances con¬ 
cerned, and the change goes no further than that 
of a purely physiological, or, strictly speaking, 
physico-chemical, accommodation. If the change 
in question is introduced in the developmental 
period of the individual, the members and organs 
mature may take on unusual structures 
and assume aberrant or variant forms, while if 
the resting seed or spore is germinated under 
altered conditions, all purely irritational re¬ 
sponses are eliminated and the entire individual 
may show a more or less atypic ontogenetic pro¬ 

This somatic variability in response to environ¬ 
ment is a matter of common observation, but de¬ 
viations of this character are of hut little impor¬ 
tance in heredity unless they or their effects are 
repeated in successive generations. This trans¬ 
mission of somatogenically induced characters is 
the cause of our confusion and the source of our 
doubts, constituting as it does the essence of the 
controversy as to the 44 heredity of acquired char¬ 
acters.” On the one hand Weismannists predi¬ 
cate an isolated current of heredity coursing from 
germ-cell to germ-cell, yielding qualities that 
direct ontogeny, but receiving nothing in return 
except nutrition and continuance, while on the 
other hand a by no means voiceless constituency 
presses for the acceptance of the conclusion that 



every wave of variability and every impress of 
the environment upon the soma are communi¬ 
cated from it to the germ-plasm upon which it 
becomes forever indelibly engraved. When to 
this claim there is added the assumption that while 
the effect of a single external impression may be 
very slight, its repetition, rhythmically or other¬ 
wise, would finally cumulate to produce appre¬ 
ciable and lasting effects, we have a conception 
difficult to prove or disprove, especially since it 
is a well-established fact that repetition of stimu¬ 
lation does give cumulative effects in both irrito- 
motility and variability. The whole question, 
however, resolves itself into the comparatively 
simple inquiry as to the physiological connections 
and correlations of the soma and germ-plasm. 

It is well known that not all of the various 
organs or tracts of tissue are directly affected 
alike by any external factor, a result due to the 
essential differences of the cells composing them. 
Thus an arid atmosphere or intense insolation 
would affect leaf activities chiefly, while unusual 
soil concentrations would influence roots only. 
The various members of the root and shoot are 
in close correlation, however, and the activity, 
growth, and mode of development of organs not 
directly acted upon by the factors mentioned may 
be profoundly influenced by the altered products 
of the organs that are affected. Thus the wound¬ 
ing of a root is reflected by changes in the shoot, 
the removal of one of the parts of a compound 



leaf causes adjustments in the remaining ones, 
and instances might be multiplied almost indef¬ 
initely to show that effects produced in one part 
are quickly and forcefully transmitted to other 
parts of the soma. It matters not for the pres¬ 
ent whether the means of communication be spe¬ 
cial tracts, nervous mechanisms, chains of cata¬ 
lytic reactions, or what other method of com¬ 


Similar communications between the egg and 
soma are to be encountered. In some of the car- 
potropic and gametropic movements of seed- 
plants, the accomplishments of definite stages in 
the development of the embryo-sac and fertiliza¬ 
tion, result in impulses to stems and peduncles 
several centimeters distant, producing move¬ 
ments and morphogenic alterations of a very 
striking character. Without further enlarge¬ 
ment on this theme it is to be said that the securest 
foundation is laid for the conclusion that well- 
defined correlations exist in the plant by which 
secondary effects of the action of external factors, 
or of morphogenic or embryonic procedure, 
may he freely communicated from one part of 
the soma to another, and from the egg to the 

With such a substantial substratum of estab¬ 
lished facts, we now turn to the problem as to 
the communication of effects from the soma to the 



egg or sperm, in such manner that these effects 
would be transmitted to succeeding generations. 

The most obvious and the most primal relation 
between the soma and the egg is the nutritive one, 
and a review of the evidence offered by Pictet 
and others leads to the conclusion that the char¬ 
acter of the building material supplied to the egg 
as varied by environmental influences may work 
changes that pass from one generation to an¬ 
other, so that it is indubitably established that the 
egg is not isolated and possessed of such highly 
developed selective power that it may avoid the 
intrusion of unusual substances. 

The experiments of Oscar Riddle, S. H. and 
S. P. Gage , 1 in which it was shown that Sudan 
III, a dye, fed to a hen, results in the coloration 
of the yolk of her eggs, and that the chicks 
hatched from such eggs take up the dye from the 
yolk, which finds a lodgment in their own fatty 
tissues, are of special interest in this connection. 

Actual available evidence does not warrant us 
in predicating any other form of influence of in¬ 
ternal region upon the germ-plasm as it takes 
form and special activity in the egg and sperm, 
beyond that of physio-chemical processes orig¬ 
inating in the soma. Alterations in these proc¬ 
esses which might affect the egg and be registered 
in its hereditary activities might occur at any 
stage of the ontogeny without direct reference to 
the time intervening between the reception of the 

1 Science, 28 : 494 . 1908 . 



stimulus and the reception of a possible impress 
by the egg. 

Concerning the results from repetition of 
stimuli in a series of generations, about the only 
facts at hand are those obtained from a study 
of variability as affected by nutrition, in which 
it is found that more favorable conditions of nu¬ 
trition increase the range, and that further in¬ 
creases accumulate with the continuance or repe¬ 
tition of the optimal conditions with relation to 
successive generations. The foregoing may be 
taken as a fair representation of the physiolog¬ 
ical basis of the possibilities by which alterations 
in the soma might be impressed upon the germ- 
plasm and transmitted to successive generations, 
and a description of the authenticated observa¬ 
tions and well-ordered experiments which have 
been made by skilled workers in dealing with this 
subject during the last few decades would form 
no mean record. It would entail a historical re¬ 
view far too voluminous for the present occasion. 
However, among other general features it appears 
that plants moved to habitats and to cultivated 
fields to the northward and southward have been 
seen to take on a seasonal rhythm in accordance 
with the new climatic conditions encountered. 
Unusual temperatures and foods have caused 
marked alterations in structure, markings, com¬ 
position of the body, periodicity of reproduction 
and range of adjustment and endurance in both 
plants and animals, but in all of these cases the 



alteration gradually disappeared when the induc¬ 
ing conditions were removed, except in a few 
instances in which it could not be demonstrated 
that the germ-plasm had not been directly 

Butterflies, moths, fishes, crustaceans, birds, 
guinea pigs, rabbits, trees, fungi, cereals, and 
bulbous plants have all been drawn into the ex¬ 
perimental field with a remarkable unanimity of 
negation in so far as the somatogenic induction 
of characters was solely concerned, which might 
he fully transmissible to successive generations 
not under the influence of the exciting factors. 
Temperature, light, food, and composition of the 
medium or substratum all have been tested in 
their various effects. Only when the germ-plasm 
has been acted upon simultaneously with the 
soma has any well-defined reappearance of in¬ 
duced characters in succeeding generations been 
noted, and of the earlier results those of Stand- 
fuss and Fischer seem most notable, since in ex¬ 
periments with Vanessa and Arctia the applica¬ 
tion of special temperatures or the modification 
of nutritive conditions induced the formation of 
aberrant characters in some of the offspring. The 
new qualities were displayed in varying degree, 
and maintained their distinctive appearance in 
the products of hybridization with the parental 
strain. There seems to be some doubt among 
zoologists acquainted with these forms as to the 
significance of these results. It is not clear as 



to the manner in which the formation of the new 
characters was induced. The experimental agen¬ 
cies employed affected both the soma and the 
germ-plasm segregated in the reproductive ele¬ 
ments, and no interpretation of the facts would 
justify the conclusion that the aberrant qualities 
were somatogenically acquired. 

While failure has attended all efforts to dem¬ 
onstrate the continued inheritance of impressions 
received by the body alone, a number of arrange¬ 
ments are found in nature which seem to demand 
such action for their explanation. Among these 
certain rudimentary organs, and also co-adapta¬ 
tions in which simultaneous specialization occur¬ 
ring in two or more members of the body has 
made for increased fitness, are difficult of inter¬ 
pretation without the interposition of somatic 



Meanwhile the possibility of influencing hered¬ 
ity by agencies acting directly upon the germ- 
cells has awakened the keenest interest among 
biologists. The relations of soma and germ- 
plasm make it difficult to induce changes in the 
body without affecting the reproductive elements, 
while it is possible to devise experimental meth¬ 
ods by which the egg or sperm alone may be sub¬ 
jected to modifying agencies. This has been 
done with such success that some very important 


Fig. 1. Leptinotarsa undecimlineata, normal form. 

Fig. 2 . Form derived from L. undecimlineata through the application of the 
climatic conditions. For convenience this form has been called angustovittata be¬ 
cause it most closely resembles a species described by Jacoby, butitdiffers from 
angustovittata in many characters considered important by the systematists. 
[From Plate 16, Investigation of Evolution in Chrysomelid Beetles of the genus 
Leptinotarsa. Carnegie Institution, Publication No. 48, 1903. After Tower.] 

Figs. 3, 4. Normal mitosis of nuclei in cells of plant. 

Figs. 5, 6, 7 , 8. Irregularities of mitosis in cells of onion roots resulting from 
exposure to radium. [After Gager.] 



conclusions may be founded upon the evidence 
obtained. The results of the work by Tower, in 
which beetles of the genus Leptinotarsa were 
subjected to various combinations and alterations 
in climatic conditions in a series of experiments 
carried on for a period of more than twelve years, 
have recently been available and far surpass in 
importance anything previously obtained from 
animals. The value of the evidence is greatly 
enhanced by its repetition, by the fact that pedi¬ 
greed cultures were used and conditions so regu¬ 
lated that an accurate analysis of the effects of 
the various climatic factors could be made. 

Professor Tower finds that:— 

“ Not only members of the genus Leptinotarsa, but 
also of allied genera can be directly modified by the 
application of intense environmental stimuli to the 
germinal material. The use of temperature and 
moisture in unusual degrees of intensity has given rise 
to a number of forms and modified characters. Some 
notion of the extent of these modifications is gained 
from the two following illustrations. In Plate I, 
Figure 1, is shown the normal form of L. undecimline- 
atci, and in Figure 2, a race derived from it by the 
application of low temperature and low relative humid¬ 
ity. This new form resembles in some respects Jacoby’s 
species L. angustovittata , and breeds true. It matters 
not whether this new form is a species, race, elementary 
species, or a nightmare to the systematist, the important 
point is, that as the result of subjecting the germinal 
material to certain conditions at a fixed point in its 
development, that the eggs thus treated, when fertilized 
by normal male germs, gave the form shown, which 
breeds true without subsequent segregation of charac- 

1 26 


ters. In this case both structural and color char¬ 
acters are modified. 

44 Many other illustrations might be given of the 
entire change in the coloration of body, both in larvae 
or adult, of the modifications of parts and of particular 
portions of the body or of individual color marks. These 
arise, some from the treatment of the male germinal ma¬ 
terial, some from treatment of the female germinal sub¬ 
stance, others from a treatment of both germinal ma¬ 
terials to the conditions of experiment. In some of 
the modifications thus induced, the full expression of 
the change is attained at once in the individuals that 
develop from the treated germs, and in others it 
requires one, two, three or more generations to attain 
the full expression of the modified attribute. It does 
not make any difference whether the full development of 
the modification is attained at once, or after the lapse 
of several generations, the behavior is the same, in that 
there is no regression or reversion to the parental con¬ 

44 In my published work I have given some of the 
results derived from the application of external factors 
at one stage of the germ cells. Eggs that have been 
subjected to the conditions of experiment immediately 
before the maturation period, have given the results 
now in print and it was from eggs so treated that the 
race illustrated in this statement came. Analysis of 
the results from these experiments shows a number of 
interesting points. 

44 First: Not all of the germ-cells are modified, but 
only a varying proportion of them, which may indicate 
one of two things; either that there are differences 
between the eggs in their capacity for modification, or 
that only certain eggs were in the proper stage for 
modification, at the time of the application of the experi¬ 
mental conditions. Second: The results are sometimes 
modifications all in one direction, at others they are in 
many directions, two, three or more different forms 
arising from the same experiment. Third: The mod- 



ifications in some characters stand apart from the condi¬ 
tion of the parents without intergrades, at other times 
the same modifications have intergrades; some charac¬ 
ters, as far as known, never have intergrades and some 
always show them, and there is no place where one can 
draw a line and say that on one side all are discontinu¬ 
ous variations and on the other side they are continuous. 
Fourth: The modifications produced never, as far as 
known, segregate the characters in subsequent genera¬ 
tions, indicating a condition different from hybrids. In 
this respect my results are like those of MacDougal 
with plants.” 

Obviously the subjection of an entire organism 
to the influence of an enveloping factor implies 
also its action upon the soma as well as upon the 
germ, and while necessarily the possibility of 
some secondary or parallel inductions are not 
entirely eliminated, yet an examination of the 
detail of the experiments points unerringly to 
the conclusion that the major effect is due to the 
action of the external agency on the egg or sperm. 
The soma is indeed the most immediate environ¬ 
ment and medium of the germ-plasm, and its 
activities must interlock most intricately with 
those of the egg and sperm, in what manner has 
already been suggested. 


Somewhat easier of analysis are the effects 
produced by such forms of energy as radiation 
of known character and measured wave-length 
as illustrated by the results secured by the use of 
X-rays, Roentgen rays, and radium emanations. 



In general it may be said that such forms of 
energy retard growth and compel an incomplete 
differentiation of tissues when applied to an indi¬ 
vidual before maturity, producing serious delete¬ 
rious effects if applied afterward. When eggs 
or sperm are treated by these agents, the most 
profound disturbances may ensue in the primary 
divisions, and the ontogeny of individuals aris¬ 
ing from a fertilization, either component in 
which has been subject to such action, shows a 
destruction of correlations and great disturbances 
in symmetry, according to the most recent tests 
of MacGregor with frogs. In most of these 
cases the disturbances were so great that the indi¬ 
viduals concerned were incapable of reproduc¬ 
tion, and nothing further concerning their effect 
on heredity was possible. The fact that the re¬ 
sults were of the same general character, whether 
the egg or sperm was subjected to the action of 
the experimental agency, whether held in the re¬ 
productive tracts of the animal or wholly free, is 
a matter of some importance, since it eliminated 
the intervention of the soma as a possible source 
of modification of the results. 

Recently Dr. C. S. Gager has completed an 
extensive study of the influence of radium on 
plants so applied that the elements subjected to 
its action survived and were capable of reproduc¬ 
tion. An examination of the effects on the nu¬ 
cleus as well as the structure of the soma was 
made with some highly interesting results. 



When the root tips of the onion (Allium cepa) 
were exposed for different periods of time to rays 
from radium bromide of various degrees of activ¬ 
ity, profound alterations were induced in the 
mitoses of the cells. In nearly all cases the 
passage of the chromosomes to the poles of the 
spindle proceeded with great irregularity. Fre¬ 
quently one or two chromosomes would remain 
behind near the equator of the spindle, failing 
completely to take part in the organization of the 
daughter nuclei (Plate I, Fig. 6). At times 
several chromosomes or portions of chromosomes 
would remain at one side of the spindle, or be 
carried beyond the poles (Fig. 8), or again be 
drawn out as if subjected to considerable tension 
(Fig. 5). In one instance, after the main cell- 
division was nearly completed, a small secondary 
spindle, in tardy telephase, was observed at one 
side of the cell (Fig. 7 ). 

From these results it was seen that the radium 
treatment afforded a method by which chromatin 
elements might be eliminated from reproductive 
cells, and if these are the carriers of certain spe¬ 
cific characters, as indicated by the researches of 
Wilson, then a ready means of suppression or 
substitution of characters would be afforded. In 
addition to these distinctly radical effects, the 
chromatin might be modified so as to form the 
basis of characters not hitherto expressed by 
the organism. 

Proceeding on this basis, Gager exposed to 



radium rays the egg and sperm-cells of carefully 
pedigreed Onagra biennis at various periods of 
their development, both before and during fertil¬ 
ization. Plants grown from the seeds produced 
under this influence varied profoundly from their 
parents. Old characters disappeared, and new 
ones became evident. The treatment followed 
by heritable alterations was one in which the pol¬ 
len grains were exposed for twenty-four hours to 
rays from radium of 1,500,000 activity, con¬ 
tained in a sealed glass tube. Thus only the 
X-rays and possibly the more penetrating of the 
Beta-rays were effective. The three individuals 
with thick, leathery leaves, which resulted from 
this treatment of the pollen, have already pro¬ 
duced a second generation in which the new char¬ 
acters are seen to be reproduced, and, while await¬ 
ing the continuance of this work, it may be as¬ 
sumed with fair certainty that the atypic strain 
will continue its development parallel to the pa¬ 
rental one. 

Other striking departures in ontogeny were 
secured by exposure of the pollen and the ovary 
before and after fertilization, and also by treat¬ 
ment of maturing seeds, which were not transmis¬ 
sible. Some slight modification of the technique 
might well secure more extensive results and also 
permit an analysis of the difference, if any, be¬ 
tween somatogenic and oogenic inductions and 
also illuminate the matter of the appearance of 




The idea that solutions of various kinds might 
be introduced into the plant, and that modifica¬ 
tions of the ontogenetic procedure might be thus 
brought about, has been in the minds of many 
workers in the laboratory. Developing inflor¬ 
escences have been excised and set in vessels con¬ 
taining salt solutions, and in other cases sub¬ 
stances were applied to cut surfaces of the vege¬ 
tative parts of the reproductive organs without 

This in part was suggested to Darwin by vege¬ 
table galls, and in the first chapter of the Origin 
of Species (page 7) we find him saying:— 

44 Such facts as the complex and extraordinary out¬ 
growths which invariably follow from the insertion of 
a minute drop of poison by a gall-producing insect, 
show us what singular modification might result in the 
case of plants from a chemical change in the nature of 
the sap.” 

That his interest in this matter was continued 
is evidenced by the following from Life and 
Letters :— 

44 Shortly before his death, my father began to 
experimentise on the possibility of producing galls arti¬ 
ficially. A letter to Sir J. D. Hooker (November 3, 
1880) shows the interest he felt in the question:— 

44 4 I was delighted with Paget’s Essay. 1 I hear 

1 Disease in Plants, by Sir James Paget. Gardeners' Chronicle , 




that he has occasionally attended to this subject from his 
youth. ... I am very glad he has called attention to 
galls: this has always seemed to me a profoundly in¬ 
teresting subject; and if I had been younger would take 
it up.’ 

“ His interest in this subject was connected with his 
ever-present wish to learn something of the causes of 
variation. He imagined to himself wonderful galls 
caused to appear on the ovaries of plants, and by these 
means he thought it possible that the seed might be 
influenced, and thus new varieties arise. He made a 
considerable number of experiments by injecting 
various reagents into the tissues of leaves, and with some 
slight indications of success.” 1 

In response to a request for a more detailed 
account of work that may have been done on this 
subject by the elder Darwin, Professor Francis 
Darwin writes under date of November 27, 

“ I am sorry that I can give you no further informa¬ 
tion about the experiments on galls. My recollection 
is that we tried only injections with leaves and stems, 
and that no actual experiments were made on ovaries. 
I have never looked at his notes and do not know where 
they are at this moment, but I feel pretty sure that no 
definite results were obtained. I think acetic or formic 
acid was used in the experiments.” 

In the course of my extensive cultures dealing 
with mutations, the theoretical conclusions of 
DeVries as to the pre-mutation period came up 
for serious consideration, and in order to obtain 
some evidence upon this point, as well as to test 
the assumption that the actual changes upon 

1 Life and Letters of Charles Darwin, by F. Darwin, II, p. 517, 
1905. New York. 


T. T. Upper and lower aspects of rosette of (Eiiothera biennis. 

1). D. Rosette of derivative resulting from ovarial treatment with zinc sulphate. 



which mutation rests ensue previous to the reduc¬ 
tion divisions leading to the formation of the 
reproductive nuclei, some new methods of experi¬ 
mentation were developed. Among other opera¬ 
tions, solutions of sugar, calcium, potassium, and 
zinc were injected by the use of hypodermic 
syringes into the developing ovaries of Raiman- 
nia, one of the evening primroses, early in 1905, 
with the result that out of the several hundreds 
of seeds borne by the treated ovaries sixteen in¬ 
dividuals were found to be notably atypic, among 
other characters lacking the trichomes which are 
so conspicuous with the parental form. These 
reproduced themselves in the second and third 
generations, coming true to the newly assumed 

The same method was tried with Oenothera 
biennis (Plate II), the common evening prim¬ 
rose of waste lands in eastern United States, with 
the result that two individuals were found among 
the seedlings which were different from the par¬ 
ents in a series of characters so distributed 
through the ontogenetic period that the deriva¬ 
tives 1 could be recognized by the first two leaves, 
while the cotyledons were still waxing. This 
form is now being cultivated at the Desert Lab¬ 
oratory in the fifth generation, and is being 
thrown against the climatic selective factors in 
the mountain plantations at various altitudes. 

1 The derivatives, lettered D in Plate II, are to be compared 
with the typical young plants, lettered T. 



These two successes had been scored by the use 
of crude instruments, entire lack of information 

Schematic section of ovule showing action of reagent, intro¬ 
duced into ovary, mi, micropyle, P, egg, a, antipodal nuclei, i, 
inner integument. The reagent is taken up by the micropylar 
cells, and also follows the stream of nutritive material around 
the inner integument to the neighborhood of the antipodal cells. 



as to the mechanical action of the reagents, and 
with plants offering an ovarial structure most 
difficult to deal with. In the development of the 
method, non-corrosive syringes of glass with gold 
needles and an extended list of substances were 
employed, while a selection of species was made 
in which the reagents could be brought into con¬ 
tact with the egg apparatus with proportionately 
least damage to its somatic structures. The sub¬ 
stitution of dyes for the substances to be used 
was found useful in making out the mechanical 
results of an injection. Since these operations 
inevitably resulted in the destruction of a large 
number of ovules, it was found most convenient 
to work with forms which are characterized by 
many-seeded ovaries. By this development of 
technique, more important results capable of def¬ 
inite analysis were secured and a fair basis for a 
theoretical explanation gained. 

Many progenies representing genera in widely 
separated families are now under observation, but 
announcement of results beyond those of a year 
ago will be confined to Penstemon. 

Penstemon wrightii is a species well marked 
and readily separable from its nearest relatives, 
which alone of the genus inhabits the slopes 
around the Desert Laboratory. It is, therefore, 
growing under perfectly undisturbed conditions. 
Various injections of zinc, calcium, and iodine 
into the young ovaries were made when these 
structures were not more than 3 mm. long and 



two-thirds of that diameter. A large number of 
the ovaries were killed by this treatment, but 
many matured. The percentage of germination 
in the species has been found to be low, however, 
and of the few hundreds of seeds sown, not more 
than a fifth germinated, and a few were killed by 
drought. Eighty individuals grew to make ma¬ 
ture rosettes during 1908. Sixty of these pro¬ 
gressed so far as to bloom during the season, and 
of these, twenty offered such material departures 
from the parental form as to be readily distin¬ 
guishable by visitors who had not critically ex¬ 
amined any member of the genus, or, indeed, had 
but little knowledge of plants. These twenty 
derivatives showed eight distinct types, one of 
which was represented by five individuals, one by 
four, two by three, one by two, and three by one. 
One type resulted from treatments with iodine, 
calcium, and zinc; four types came from a treat¬ 
ment of two reagents, two from iodine alone, and 
two from calcium alone. The revolution of the 
corolla segments, the absence of the stiff clump 
of trichomes from the lower lip, increase in vis¬ 
cidity, mottling of the flower, and adhesion of leaf 
bases resulting in perfoliation, are some of the 
distinguishing marks of the new forms. Of these 
characters some are already displayed by other 
members of the genus, while some of the progres¬ 
sive and retrogressive changes seem to be taken 
before any relative had moved in the same direc¬ 



Briefly summarizing the results of the investi¬ 
gations cited it may be taken as safely established 
that individually acquired or induced characters 
or modifications of existing qualities may he 
transmitted from one generation to another prac¬ 
tically unchanged. The assumption that organ¬ 
isms may make direct fitting or adaptive re¬ 
sponses of the soma to environmental factors, 
which may be impressed on the germ-plasm and 
transmitted to successive generations, has not 
been confirmed by actual observation or experi¬ 
mental tests. 

This tentative conclusion that somatogenic 
characters are not transmitted is one with which 
the following facts must always be taken into 
account: A —the physiological mechanism of or¬ 
ganisms, particularly of the seed-plants, is one 
which offers direct means of communication be¬ 
tween the soma and the germ-plasm in the form 
of reproductive elements, and which might per¬ 
mit the making of enduring impressions on 
embryonic tissues during ontogeny, or their 
effective communication to the egg, or sperm; 
B —the experimental and cultural test of the 
effect of repetition of the action of external agen¬ 
cies upon the soma in inducing hereditary alter¬ 
ation has not yet been seriously attempted, and 
may indeed include the crucial requisite of the 
whole matter; C —a great number of structures 
and functions sustain the closest adaptive relation 
to environic forces, and important correlations 



are found among or between organs in a manner 
difficult of explanation upon any ground except 
that of simultaneous somatogenic induction. 


The modification of heredity brought about by 
the direct action of various agencies upon the 
germ-plasm is now safely established, and the 
available results are sufficient to justify some few 
generalizations as to the mechanism of the 
change. The most important evidence as to the 
nature of the disturbances which may ensue in 
reproductive elements comes from the work of 
Gager, who found that the action of radium 
might eliminate definite chromatin elements dur¬ 
ing the mitoses of the egg and pollen, and, fur¬ 
thermore, that some of the eggs fertilized by 
pollen subjected to such irradiation produced a 
progeny in which qualities different from those of 
the parental strain were exhibited. It is not 
proven, of course, that the atypic strain was de¬ 
rived from a fertilization into which one less or 
one more chromosome entered, and possible dis¬ 
turbances of the autolytic action of the cell might 
well be as important as the departures from nor¬ 
mal mitotic procedure. The well-known influ¬ 
ence of temperatures upon these processes and 
also the readiness with which unusual substances 
might be thrown into the cytoplasm in the ordi¬ 
nary course of nutrition, suggests that the plant 



would be susceptible to modification in the stage 
between the reduction divisions and fertilization. 

This conclusion is borne out by my own results 
in which solutions were introduced into the ovary 
during this stage. The extent of the treatments, 
together with the diversity of results, makes pos¬ 
sible an analysis of other features. Thus the in¬ 
duction of more than one form by the use of a 
single reagent suggests either that different chro¬ 
matin elements were affected in the separate 
ovular reactions, or that unlike parts of the chains 
of catalytic action were interrupted or disturbed 
by the introduced substances. Some of the com¬ 
pounds used are inimical to enzymatic action, or 
may be capable of a negatively catalytic effect, 
or might indeed set up unusual splitting proc¬ 
esses, a state of affairs distinctly favorable to the 
last named alternative. 

Not only may irradiation and the introduction 
of unusual substances occur naturally to the mod¬ 
ification of heredity in plants, but the climatic 
factors may, as in Tower’s experiments, exercise 
an influence upon the reaction velocities of va¬ 
rious parts of the metabolic series, or by varia¬ 
tions in humidity, regulate the excretion or reten¬ 
tion of active substances. All of these possibilities 
must be taken into account in attempts at expla¬ 
nation of bud-sports or bud-mutations in plants. 
It is to be seen that either egg or sperm may be 
affected by experimental agencies, and that the 
results do not differ in quality or degree. Gager’s 



atypic forms were obtained by the treatment of 
pollen; my own from ovarial injections which 
might have acted upon the egg, or sperm, and 
Tower’s work was with both. 

The new forms of beetles and plants which 
have thus been called into existence sustain the 
following general relations to their environ¬ 
ment and to the strains from which they were 

1. Some of the species dealt with were growing 
in the open, and domesticated forms were not in¬ 
cluded in the experiments. 

2. The newly arisen or modified characters 
maintained their distinctive appearance when 
crossed with the parental strains; in some no re¬ 
versions have yet been shown. 

3. Discontinuous departures induced by ova¬ 
rial treatments in plants were full and constant 
within the limits of fiuctuability with the first 
generation. Similar abruptness of divergence is 
exhibited by beetles in some cases, while in others 
more than one generation, after removal from 
experimental conditions, was necessary to secure 
full expression. 

4. Many aberrations induced by irradiation in 
plants and by climatic effects in beetles were of 
the nature of closely continuous variations, the 
range of which was widened by the exciting 
agent. Some of the derivatives of Penstemon 
may prove to be of this character. The single 
derivative of Oenothera biennis obtained by ova- 



rial treatment with zinc sulphate is distinctly 
discontinuous with the parent. 

5. Some of the modifications may be regarded 
as an increase of capacities already present; some 
imply the loss of characters or structures, and 
some are acquisitions; in more than one instance 
qualities new to the genus have been taken on. 
Changes such as the mottling of a solidly col¬ 
ored flower may be regarded as a loss of a por¬ 
tion of a design, the total effect of which was a 
shaded or a self color, or it may be taken as a 
differentiation in advance. 

6. The behavior of the newly derived forms 
when subjected to natural conditions, competi¬ 
tion, and possibility of hybridization with paren¬ 
tal forms, has been extremely diverse. Some of 
the beetles have been swamped by hybridization 
with the parental form; others have displayed 
some power of endurance. The plant deriva¬ 
tives induced by ovarial treatments were weaker 
than the parent in some localities, and more en¬ 
during in others. The derivative of Oenothera 
biennis induced by a zinc sulphate ovarial treat¬ 
ment is less adapted to xerophytic conditions 
than the parent, does not readily hybridize with 
it when grown in contact, and its earlier char¬ 
acters appear to be dominant when crosses are 
made artificially. 

7. The departures obtained by the experi¬ 
mental manipulation of external exciting agen¬ 
cies bear a general similarity to the initiatory 


and modificational phenomena exhibited by or¬ 
ganisms in a state of nature, and it seems justi¬ 
fiable to conclude that the processes disturbed or 
set in motion are identical with some of those 
concerned in the main evolutionary development 
of organisms. 




No one recognizes more frankly and joyously 
than would Darwin, were he here to-day, the 
great advance which has been made in our knowl¬ 
edge of heredity since his time. His work and 
writings have pointed the way to that advance, 
and it is largely owing to a return to the experi¬ 
mental method of testing hypotheses, which Dar¬ 
win used so successfully, that the remarkable 
progress of the last decade has been made pos¬ 
sible. We do, therefore, the greatest honor to 
Darwin if we pause to consider what superstruc¬ 
ture of knowledge has been built on the founda¬ 
tions which he laid. This superstructure is, in¬ 
deed, still in the building, and it is not easy in 
all cases to distinguish between the solid structure 
of proved fact and the scaffolding of hypothesis. 
Still, the attempt should be made, and it will 
give us encouragement to discover that, notwith¬ 
standing the considerable amount of rubbish 
lying about, there is, nevertheless, good con¬ 
structive work going on here which gives prom¬ 
ise of permanency. 




The particular topic which I have been asked 
to discuss is the behavior of unit characters in 

The subject of heredity units is one to which 
Darwin gave much thought. With characteristic 
thoroughness and patience he assembled the facts 
of inheritance, reversion, bud variation, regenera¬ 
tion, and related subjects, which in his opinion 
had a common underlying cause, and with delib¬ 
eration framed a tentative hypothesis to explain 
them. This hypothesis, which he called pangen¬ 
esis, was itself short-lived, but has left a numer¬ 
ous progeny. The most important are the idio¬ 
plasm theories of Weismann and Nageli, and the 
theory of intracellular pangenesis of De Vries. 
Darwin’s hypothesis was useful because it set 
people to thinking, observing, and experiment¬ 
ing. The theories of Weismann, Nageli, and 
De Vries were attempts to bring Darwin’s fun¬ 
damental idea into harmony with facts subse¬ 
quently discovered. All these theories were 
scaffolding, not masonry. 


A conception of unit characters fundamen¬ 
tally different from Darwin’s, one which 
antedates slightly the pangenesis theory, but 
which suffered total eclipse by it, is to-day 
known as Mendel’s law. It accords so fully 
with a variety of biological facts discovered 



since Darwin’s time, that we are coming to re¬ 
gard it as the cornerstone of our knowledge of 

The romantic story of Gregor Mendel is 
known to you, how toiling long years in obscurity 
hybridizing garden-peas, he made a great dis¬ 
covery only to see it scarce noticed and soon 
forgotten. He himself, meanwhile, called to ad¬ 
minister the affairs of an ecclesiastical establish¬ 
ment, was forced to relinquish his favorite pur¬ 
suit of scientific investigation, and was thus 
unable to follow up his great discovery and force 
it upon the attention of scientists. So he died 
unhonored by his fellow-scientists and all but 
unknown to them. 

The story of how, a generation later, Mendel’s 
law was rediscovered thrice over is scarcely less . 
romantic. That the rediscoverers, having first 
established the law independently and then hav¬ 
ing discovered Mendel, should assign the honor 
unreservedly to the obscure and forgotten Abbot 
of Briinn, is a circumstance which should cause 
us long to remember and honor the names of De 
Vries, Correns, and Tschermak. 

According to Darwin’s pangenesis theory, the 
reproductive cell is made up of minute units de¬ 
rived from and representing each part or organ 
of the entire body. A few critical experiments 
instituted by Galton showed this theory to be 
untenable, and they seem to have involved in 
public esteem an adverse decision against all less 



well-known theories in which the existence of 
units in heredity was assumed. Such was the 
fate deservedly of the highly speculative theories 
of Nageli, and undeservedly of the generalization 
reached by Gregor Mendel, a scientific protege 
of Nageli. 

Mendel did not frame any complete theory of 
heredity, but observed, as the result of experi¬ 
ment, that certain characters of plants are, in 
crosses, inherited by definite proportions of the 
offspring. He framed in general terms a state¬ 
ment of what those proportions are and advanced 
a simple hypothesis to account for them. Men¬ 
del’s generalization we know to-day as Mendel’s 
law, and his hypothesis as the theory of unit 

By a unit character in the sense of Mendel’s 
law, we mean any quality or part of an organism, 
or assemblage of qualities or parts, which can be 
shown to be transmitted in heredity as a whole 
and independently of other qualities or parts. 
Thus Mendel found that the starchy char¬ 
acter of the seed of some varieties of garden- 
peas, which makes the seeds round and smooth 
when dried, is a quality which may by suitable 
crosses be replaced by a sugary character, causing 
wrinkling of the seed on drying. This change of 
the seed character through crossing may be 
brought about without essential modification of 
the other parts of the pl'ant. Round and wrin¬ 
kled seed forms in peas, Mendel accordingly con- 



sidered to be alternative and interchangeable unit 

Similarly yellow color of the cotyledons in the 
seed of peas was found to be a unit character 
alternative with green color. In animals we find 
similar simple unit characters to exist. Thus in 
mammals black pigmentation is due to the pres¬ 
ence of a unit character which may be replaced 
by another changing the pigmentation to brown. 
Among horned ruminants, such as cattle and 
sheep, development of the horns depends upon 
the presence of a unit character which may be 
replaced by (or perhaps become associated with) 
another, in the presence of which horns fail to 


In cases less simple than these, a unit character 
may have more than a single manifestation, as 
where a plant having flowers of a certain color 
has also a similar but fainter coloration of the 
stem, or a mammal with black hair-pigment has 
also black skin-pigment, while one with brown 
hair-pigment has also brown skin-pigment. In 
still other cases, two or more independent unit 
characters must be present together to produce 
a single visible effect. This fact was unknown 
to Mendel. Its discovery constitutes one of the 
most recent and important advances made in our 



knowledge of heredity, and merits further con¬ 

Mendel conceived of unit characters as exist¬ 
ing always in pairs, one of which might be sub¬ 
stituted for the other by suitable crosses. We 
are now coming to realize that this is an inade¬ 
quate statement of the matter. What is paired 
is not the unit character alone, but the entire or¬ 
ganism. All its characters and parts have their 
basis in paired structures in the protoplasm of 
the individual, one member of each pair being 
derived from the mother of the individual, one 
from the father. The cytologist has visible evi¬ 
dence of this fact in the doubling of the number 
of chromosomes at fertilization, and their subse¬ 
quent reduction when the reproductive cells 
ripen; the experimental breeder has evidence of 
this duality equally convincing as regards many 
hereditary characters, but the evidence is clearest 
in the case of characters which occasionally are 
lost. It is only in such cases that we can with 
certainty identify unit characters. By compar¬ 
ing an individual which has a certain character 
with another individual which does not have it, 
we learn how much that character includes, and 
we can learn this in no other way. Experimen¬ 
tal breeding will show whether the character is 
simple, is really a unit, or is an aggregate of in¬ 
dependent units. Thus if we cross a black 
guinea-pig with one which lacks black—say a 
brown one—we obtain only black offspring, but 


these bred inter se produce both black offspring 
and brown ones, in the proportion three black 
to one brown. We thus learn that black is a 
unit character. It was contributed by one par¬ 
ent to the cross, but not by the other, and trans¬ 
mitted by the cross-bred individual to half its 
offspring, but not to the other half. This is 
Mendel’s explanation of the 3:1 ratio, now fa¬ 
miliar to every biologist. 

But if we cross the same black parent in the 
foregoing case, not with a brown individual, but 
with a white one or with a yellow one, we may 
obtain not black offspring, but wild-colored 
“ agouti ” ones, which bred inter se will produce 
agouti, black, white (or else yellow) young, with 
perhaps those of other new classes in addition. 
Such a result as this puzzled Darwin, and would 
naturally puzzle any one, but in the light of Men¬ 
del’s law T becomes capable of ready explanation. 
The production of black pigment is a process in 
which more than one unit character is concerned; 
the production of a gray coat involves more units 
still; how many, can in part be determined by a 
study of the number of classes of individuals 
occurring in the second generation from the 
cross, and the numerical proportions in which the 
individuals occur in these classes. The point 
may be made clearer by following through 
a particular case, to which Darwin makes 



Primary color-varieties 

of rabbits Constitutent factors 








Black . C—B—E 










Sooty . C—B—R 



If rabbits of various colors are turned loose 
together in a warren, the population is likely to 
revert more or less completely to the gray color¬ 
ation of wild rabbits. The foregoing is in sub¬ 
stance the statement of Darwin; and its correct¬ 
ness is fully established. 



Before going further it may be well to describe 
the color varieties of rabbits. These are exceed- 



ingly numerous, but for our purpose may be 
reduced to four fundamental color types in addi¬ 
tion to the albino or uncolored type. These four 
are gray, black, yellow, and sooty yellow. The 
last I shall for simplicity call sooty. Gray is the 
original or wild type from which the others have 
been derived. The gray fur contains both black 
and yellow pigments, but so disposed as to pro¬ 
duce a pattern on the individual hair, viz., a dark 
base and tip and in between them a band of yel¬ 
low. The lower surfaces of the body also are 
whitish. In the black variety the hair pattern is 
wanting, and the black pigment occurs through¬ 
out the length of each hair and all over the body. 
In the yellow variety black pigment is largely 
wanting throughout the coat, though present in 
the eye and, in very small quantities, in the hair. 
The presence of the hair-pattern is nevertheless 
suggested by whitish under surfaces, as in the 
gray type. The sooty type closely resembles the 
yellow, but has colored under surfaces, instead of 
white ones. Yellow and sooty correspond with 
gray and black respectively, but with a greatly 
reduced amount of black pigment in the fur, so 
that yellow predominates there. 

Let us now consider the relation of these four 
types one to the other. Gray crossed with any 
other type produces only gray offspring. Black 
crossed with yellow produces gray, but crossed 
with sooty produces black. Yellow crossed with 
sooty produces only yellow. Sooty disappears 



in crosses with any other type; it is recessive in 
the Mendelian sense with reference to all the 

Darwin explained the reversion of feral rab¬ 
bits to the gray type on two grounds: (1) “a 
tendency in all crossed animals to revert to their 
primordial state,” and (2) the action of a more 
“ natural ” environment when the animals are 
free than when they are in captivity. In reality 
neither of these conjectured reasons has anything 
to do with the case. Some varieties will under no 
circumstances give reversion, if crossed with each 
other; but reversion may be obtained as readily 
in captivity as anywhere. Reversion is due solely 
to the bringing together of certain unit char¬ 
acters, whose joint action is necessary to produce 
the observed result. 

In producing the gray coat characteristic of 
wild rabbits at least eight independent unit char¬ 
acters are involved. Other color varieties of the 
rabbit have arisen by regressive variation, i.e. by 
loss, more or less complete, of one or more of 
these unit characters. 

To illustrate the matter, let us consider the 
result of a particular experiment. Black rab¬ 
bits were crossed with light yellow (cream) 
ones, and produced wild-colored gray offspring. 
These bred inter se produced young of a variety 
of colors, but among them grays again predom¬ 
inated. All the first generation grays seemed 
to breed alike, producing young of various colors, 



but not so those of the second generation (F 2 ). 
Among these thirty-two different classes may be 
recognized, that is, thirty-two sorts which, though 
all looking alike, produce each a different assort¬ 
ment of young. These assortments are:— 

1. Gray only. 

2. Gray, and black. 

3. Gray, and white. 

4. Gray, black, and white. 

5. Gray, and yellow. 

6. Gray, black, yellow, and sooty. 

7. Gray, yellow, and white. 

8. Gray, black, yellow, sooty, and white. 

Eight other varieties produce the same sorts of 
young as these eight respectively, but in addition 
produce dilute pigmented ones of the same color 
types, i.e. blue-grays as well as grays, blue as 
well as black, cream as well as yellow, and pale 
sooty as well as sooty. Sixteen other varieties 
produce the same assortments of young as these 
sixteen, but in addition produce animals spotted 
with white in each of the several color types. 

The facts briefly stated are now before us. 
We can distinguish among the second generation 
gray rabbits thirty-two different kinds, all look¬ 
ing alike but all breeding differently. Out of 
this apparent chaos the Mendelian theory of unit 
characters brings law and order; no other ex¬ 
planation has been offered which makes anything 
but chaos out of the situation. The number of 
distinguishable classes, thirty-two, shows that 



five independently variable characters are in¬ 
volved ; the proportions in which the several sorts 
of young are produced by each class of gray 
parent confirms this conclusion. If the number 
of independent unit characters concerned were 
one greater, as it is in guinea-pigs, the total num¬ 
ber of classes of parents would be doubled to 
sixty-four; if it were one less, the number of 
classes of parents would he reduced one-half, to 

What now are the five variable unit characters 
concerned in producing the gray coat of a rab¬ 
bit and what are their relations one to another? 
In answering this question it will be necessary 
to mention a sixth unit character which contrib¬ 
utes to the result, though not itself variable. It 
will be convenient also to designate each sep¬ 
arate unit character by a letter or symbol. The 
six unit characters to which reference has been 
made are:— 

1. C, a general color factor, something necessary to 
the production of all pigment, wanting only in albinos. 

2. B, a factor for black, some substance, which acting 
upon C, produces black pigment; this is in rabbits an 
unvarying factor, though in other mammals it is often 

The four remaining factors modify the action of 
one or the other of these two; they are:— 

3. A, a pattern-factor governing the distribution of 
black on the individual hair, so that it converts black 
into gray, blue into blue-gray, and sooty into yellow. 



4. E, a factor governing the extension of black over 
the body generally; in its most extended distribution, 
black occurs on all hairs of the body, in its most 
restricted distribution (R) it scarcely extends beyond 
the eye, and the skin of the extremities, the hair being 
practically devoid of black pigment and appearing yel¬ 
low; that this factor is distinct from B, is shown by the 
fact that it can, in guinea-pigs, be dissociated from B 
and become associated with brown pigmentation. 

5. U, a factor governing the distribution of C over 
the body; if C covers the whole body (condition U), the 
whole body is pigmented; if C covers part of the coat 
only (condition S), the rest is occupied by spots of 
white. That this unit is distinct from C is shown by 
the fact that it is transmissible through animals which 
lack C, that is, through albinos. 

6. I, a factor governing the intensity of the pig¬ 
mentation. It is a modifier of C, for it affects all pig¬ 
ments alike, yellow and brown as well as black, all of 
which pigments have their common basis in C; but I is 
distinct from C 5 for it is transmissible through albinos, 
which lack C. When I is present all the pigments are 
intense; when I is absent, or rather weakened to the 
condition D, the pigmentation is dilute, as in blue and 
cream, the dilute conditions of black and yellow 

It is clear from what has just been said that 
these various factors, though separately variable, 
are not entirely independent of each other. Some 
produce no visible effects unless others are pres¬ 
ent. Thus if C alone is wanting, none of the 
others is visible. To aid in expressing the inter¬ 
relationship of the factors I think it useful to 
imitate the organic chemist and employ dia¬ 
grams. Thus a diagram might be constructed as 
follows to express the relations of the six factors 



in a reproductive cell transmitting the color char¬ 
acters of a gray rabbit:— 






It is possible that in protoplasm we have or¬ 
ganic molecules built up in some such way, and 
that regressive variations arise by dropping off 
the constituent parts of the molecule one by one. 
Certainly it is loss or extreme modification of 
factors that produces the ordinary color varia¬ 
tions. If A drops out, we have a black rabbit 
instead of a gray; if E is replaced by R, a yellow 
one is produced; if both these changes occur, a 
sooty one; if U is replaced by S, we have a 
spotted gray rabbit; if both U is replaced by S, 
and A is lost, a spotted black rabbit results; if 
C is lost, we have an albino, whose breeding ca¬ 
pacity varies with the number of other invisible 
factors which remain. 

The list of known color factors is not ex¬ 
hausted by those which I have enumerated. One 
other, a factor for brown pigmentation, Br, has 
been revealed in the case of the guinea-pig, the 
mouse, and the dog, by loss of factor B. Brown 
pigmentation then everywhere replaces black. 
This factor bears the same relation as does B to 
both C and E. Some time doubtless we shall see 



brown and cinnamon-gray rabbits produced by 
the same mutation, loss of factor B, which has 
produced brown and cinnamon-agouti varieties 
among mice and guinea-pigs. Again there must 
be in all rodents a factor Y which, acting in the 
presence of C, produces yellow pigment, but Y 
has not unmistakably revealed itself by getting 
lost. It is always present, if C is, and may rep¬ 
resent possibly a step on the road to the produc¬ 
tion of black and brown. Certainly, however, 
its distribution on the body of the rabbit is inde¬ 
pendent of the factor E, though subject to U. 
In the diagram, therefore, Y and Br will prob¬ 
ably fall into the positions shown herewith for 
the guinea-pig:— 

U B 

I / \ 

A—C—Y E 

I \ / 

I Br 

This diagram would express the interrelations 
of the color factors, as we now understand the 
matter, in a reproductive cell or gamete trans¬ 
mitting the wild type of coat. But such a 
gamete might be formed by some sixty-four dif¬ 
ferent kinds of wild-coated individuals. The 
only differences, however, between these sixty- 
four kinds of individuals would lie in whether 
they contained a single or a double dose of each 
of the factors enumerated. I therefore propose 



further to imitate the organic chemist by placing 
a subscript, 2 , after each factor doubly represented 
in the individual, i.e. after every factor in which 
the individual is homozygous, while elsewhere 
omitting it. We shall thus have a zygotic for¬ 
mula which will look like a chemical formula, and 
which will serve the same useful purpose of ex¬ 
pressing many facts clearly and in small com¬ 

The zygotic formula of the pure gray rabbit 
will then be B 2 E 2 A 2 C 2 I 2 U 2 ; the gray rabbit 
which also gives black young will be single in A, 
but otherwise identical in formula with the fore¬ 
going, viz., B 2 E 2 A C 2 I 2 U 2 , and so on through 
the list. 

The question will naturally suggest itself, how 
common are unit characters? Are all the quali¬ 
ties and parts of organisms due to them, or only 
certain kinds of qualities or parts? Such ques¬ 
tions can not at present be answered satisfac¬ 
torily. It may be pointed out, however, that we 
are already acquainted with a considerable va¬ 
riety of Mendelizing characters. These include 
in plants both structural and physiological char¬ 
acters of stem, leaf, flower, and seed. In ani¬ 
mals, where a less extensive study has as yet been 
made and where the organization is much more 
complex, the unit characters thus far identified 
relate chiefly to superficial characters, pigmenta¬ 
tion, hair-structure, and the like. Certain pecu¬ 
liar variations of the skeleton, digital variations, 



and the like, have, however, been shown to Men- 
delize, and further study will undoubtedly reveal 
the existence of additional unit characters. We 
should also bear in mind that we have no means 
of identifying unit characters except as they drop 
out of existence in certain individuals. Many 
unit characters are probably of such vital impor¬ 
tance to the organism that they cannot be dis¬ 
pensed with, for when they are lost the organism 
ceases to exist. In such cases the existence of 
unit characters, however probable, can not be 
unmistakably demonstrated by any method now 
known to us. Fragmentary as our present 
knowledge is, it is doubtful whether any category 
of organs, quantities, or parts can be mentioned 
which is not subject to Mendelian inheritance. 
If we could only discover some means of sup¬ 
pressing particular unit characters, what an in¬ 
strument for unraveling the mysteries of inheri¬ 
tance would be ours! 

Time does not suffice to discuss the mutability 
or immutability of the unit characters, the pos¬ 
sibility of new characters arising de novo, and 
other interesting but disputed questions. These 
are matters with which the second fifty years 
after Darwin will have to deal. 




Forty-three years after the Origin of Spe¬ 
cies there appeared the first part of a book by the 
Dutch naturalist, Hugo de Vries, entitled Die 
Mutationstheorie. Many other theories of evo¬ 
lution have been propounded and defended in the 
last half-century, but hardly any other has 
commanded such immediate consideration and 
received such widespread acceptance. The muta¬ 
tion theory must therefore contain certain evi¬ 
dent elements of truth. Let us consider its 
scope and some of the evidence on which it rests. 


First of all it is necessary to define mutation 
in De Vries’ sense and to show its relation to 
other evolutionary principles. Mutation in any 
strain is a change in the unhybridized germ- 
plasm of that strain which is characterized by the 
acquisition or loss of one or more unit charac¬ 
ters. There has already been presented to you 
the evidence for unit characters, a conception 
first clearly elucidated by Darwin. I think it 
may fairly be said that the mutation theory rests 
on the doctrine of unit characters and applies 




only so far as that doctrine applies. As even the 
most extreme neo-Darwinian school recognizes 
such units with their representatives (determin¬ 
ants of Weismann) in the egg, and as in evolu¬ 
tion there must be the acquisition or loss of at 
least some one character, it might be expected 
that the idea of mutation as defined above would 
find universal acceptance. But it has not done 
so. The difference of opinion relates to the gra¬ 
dient of the transition by which a new unit char¬ 
acter is introduced or an old one disappears. 
Mutation in De Vries’ sense implies the sudden 
appearance, complete in the first generation, of 
the new unit character and its germinal repre¬ 
sentative, the pangene or determinant. Muta¬ 
tion is regarded by many who call themselves 
Darwinians as an innovation and as opposed to 
Darwin’s fundamental assumptions. For the 
neo-Darwinian conceives the determinant as 
gradually changing in evolution and exhibiting 
in the adult forms of successive generations the 
same continuous series that an organ shows in its 
ontogenetic development. The view of neo- 
Darwinians is well indicated in the following 
quotation from Weismann 1 :— 

“ If I mistake not we may say at least so much that 
all variations are, in ultimate instances, quantitative, and 
that they depend on the increase or decrease of the vital 
particles, or their constituents, the molecules. . . . 

What appears to us a qualitative variation is, in reality, 
nothing more than a greater or less, a different mingling 
of the constituents which make up a higher unit, an 
1 The Evolution Theory, Vol. II, p. 151. 



unequal increase or decrease of these constituents, the 
lower units. We speak of the simple growth of a cell 
when its mass increases without any alteration in its 
composition . . . but the cell changes its constitution 

when this proportion is disturbed, when, for instance, 
the red pigment granules which were formerly present 
but scarcely visible increase so that the cell looks red. If 


there had previously been no red granules present, they 
might have arisen through the breaking up of certain 
particles—of protoplasm, for instance,—in the course 
of metabolism so that, among other substances, red 
granules of uric acid or some other red stuff were pro¬ 
duced. In this case, also, the qualitative change would 
depend on an increase or decrease of certain simpler 
molecules and atoms constituting the protoplasm-mole¬ 
cule. Thus, in ultimate instance, all variations depend 
upon quantitative changes of the constituents of which 
the varying part is composed.” 

So far Weismann. With his accustomed thor¬ 
oughness he has followed the consequences of his 
stand that quantitative changes alone are suf¬ 
ficient to account for the processes of evolution, 
although to do so he has been forced to take the 
position that the loss of certain atoms from a 
molecule is merely a quantitative change, and 
that the appearance of a new quality is quantita¬ 
tive because merely of the order of a change from 
zero to one! Weismann’s argument here degen¬ 
erates to a mere play of words. Just as good an 
argument could be made to support the assertion 
that all changes are qualitative—that 96 is qual¬ 
itatively unlike 97. But if the ideas are both 
to be retained, then it must be admitted that a 
loss of atoms from a molecule, the appearance of 



a new kind of molecule, the appearance of red 
pigment where none was, are all qualitative 
changes. Weismann’s admission that red gran¬ 
ules may arise de novo in consequence of a molec¬ 
ular change in the germ-plasm is an admission 
that an organism may undergo a qualitative va¬ 
riation, and this is a mutation. Recalling, then, 
in recapitulation, that every character of an or¬ 
ganism has a chemical basis, that a new character 
implies one or more new kinds of molecules and 
that molecular change is essentially qualitative 
and discontinuous, the conclusion seems safe that 
variations involving new characters are essen¬ 
tially discontinuous, and consequently of the 
order of mutations. 


At this time the Weismannian view and that 
of the neo-Darwinists in general is of less interest 
than that of Darwin himself. What was Dar¬ 
win’s attitude on the question whether variations 
that play a part in evolution are of the qualita¬ 
tive or the quantitative order? The answer 
seems to be simple; the question did not present 
itself to him—our formulation of the matter is 
a comparatively recent product of scientific anal¬ 
ysis. Darwin did recognize saltation as opposed 
to ordinary variability, and remarks: “ It is dif¬ 
ficult to drawn any distinct line between a vari¬ 
ation and a monstrosity.” In his Variation of 
Animals and Plants under Domestication , Dar- 



win cites cases of characteristics that he believes 
to have arisen suddenly, such as the blackness of 
the japanned peacock, jaw appendages of pigs, 
short upper jaw and hornlessness in cattle, short - 
leggedness in sheep and dogs, elongated wool in 
merinos, and downless fruit in peaches. These 
instances sufficiently indicate Darwin’s recogni¬ 
tion of saltation, and if he was led to reject it as 
the usual mode of modification of species, he did 
so because the doctrine had a crude form and car¬ 
ried with it the connotation of something terato- 
logical or pathological. But is there sufficient 
evidence that, in rejecting saltation, he regarded 
evolutionary changes in unit characters to pro¬ 
ceed always by the fourth place of decimals? 
On the contrary, his examples of variations are 
very unlike the raw material of the biometric 
school. This is a sample of his idea of variation 
in poultry:— 

“ The tarsi are often feathered. The feet in many 
breeds are furnished with additional toes. Golden 
spangled Polish fowls are said to have the skin between 
the toes well developed.” 

In the short section labeled “ Remarkable va¬ 
riations of Goats,” Darwin refers to the great 
ears of goats of the Island of Mauritius, to the 
various forms of mammae, to throat appendages, 
hornlessness, and presence or absence of toe 
glands. The entire work on Variation under 
Domestication demonstrates that Darwin fre¬ 
quently, if not usually, meant by Variation the 



acquisition or loss of unit characters. Darwin’s 
position has been sadly misrepresented by those 
neo-Darwinians who have insisted that Natural 
Selection operates only upon variations of the 
quantitative order. In the Origin of Species, 
Darwin was arguing for continuity and natural 
law, and accepted the principle “ natura non facit 
saltum ” as in accord with the new view. Con¬ 
tinuity in nature was his great argument against 
creation. “ Why,” he asks, “ should all the parts 
and organs of many independent beings, each 
supposed to have been separately created for its 
special place in nature, be so invariably linked 
together by gradated steps? ” Fifty years ago, 
we must remember, it was the battle of continu¬ 
ity against special creation that was being fought 
and not the gradual as opposed to the sudden 
appearance of a unit character. 

Recognizing, then, that the mutation theory, 
far from being opposed to Darwin’s theory of 
the origin of species, would have been welcomed 
by him, we pass with more satisfaction, on the 
occasion of this celebration, to a detailed consid¬ 
eration of some of the facts of mutation. 


The classical case of mutation is that of the 
evening primrose, named after Lamarck, but 
henceforth to be no less closely linked with the 
name of his evolutionary successor, De Vries. 



Here is a plant of characteristic form and flower 
which regularly produces a small percentage of 
offspring of strikingly different forms—sparsely 
branched instead of profusely, with brittle leaves 
instead of smooth, of stunted size and small flow¬ 
ers, with strap-shaped or with ovoidal leaves in 
place of lanceolate. The unit characters that 
appear in these peculiar progeny of lamarckiana 
do not intergrade with the corresponding charac¬ 
ters of the parents, and, on self-fertilization, are 
reproduced in successive generations. 

While the particular kind of mutation exhib¬ 
ited by Lamarck’s primrose is rare, it is common 
to find species in which an organ appears, in dif¬ 
ferent individuals, in a number of distinct forms 
constituting the so-called “ elementary species ” 
—a term that seems justified since, bred to their 
like, these forms are reproduced in successive 
generations. Striking examples of this sort have 
been found in wild violets by Doctor Ezra Brain- 
erd, and in the shepherd’s purse by Doctors 
Lotsy and Shull. Animals have been less care¬ 
fully scrutinized for elementary species; but we 
are not without instances. The true bugs and 
the straight-winged insects often show both long¬ 
winged and short-winged forms, without inter¬ 
grades. Some tiger beetles, of both sexes, appear 
either in a brown or a blue-green dress. Wheeler 
has collected over a score of pink katydids discov¬ 
ered in the United States within recent years, and 
has noted cases of pink forms of green hemip- 



tera. The same green species sometimes have a 
brown form, too. In these cases the new char¬ 
acters of pinkness and of brownness have un¬ 
doubtedly arisen suddenly and no intergrades are 
known. Of the common May beetle, I am in¬ 
formed by Professor Forbes, no less than forty- 
two forms are known from Illinois alone, several 
of them difficult to distinguish by superficial 
characters, all of them readily separated by ref¬ 
erence to the copulatory structures, which are dif¬ 
ferent in the various species and in the two sexes. 
“ These structures are so constant,” writes Pro¬ 
fessor Forbes, “that one of my assistants who 
has handled over ten thousand specimens of one 
species for determination, says that they are all 
like castings from the same mold.” There are 
features of this case that certainly look like mu¬ 
tation; particularly the large number of species 
in a small area separated by non-intergrading 
differences in one variable organ. But, as Pro¬ 
fessor Forbes suggests, there is one difficulty in 
the way of seeing how the differences could have 
arisen by mutation: the copulating organs in each 
species are mechanically adapted to each other; 
and this requires that a coincident and coadaptive 
mutation occur in the two sexes. But this is a 
true difficulty only so long as we conceive the 
entire organ to be a single unit character. There 
is, however, as little reason for so conceiving it 
as for regarding the human hand as one unit 
character instead of many units. The evolu- 



tion of mutually adapted sex organs may be 
readily conceived as follows: Let a new species 
differ from its ancestor by a character m ; then, 
in accordance with the familiar fact of sex dimor¬ 
phism in unit characters this takes in the two 
sexes the forms m and m"’. If the two sex-forms 
are incompatible the new species will come to 
nought; but if not incompatible the two modi¬ 
fied sexes may interbreed and be prevented from 
breeding with the parent species. By the addition 
of a series of new unit characters, n 3 o, p 3 etc.— 
each of which must stand the test of compatibility 
in the two sexes—a complex dimorphic organ may 
be built up by mutation. It were wearisome to 
attempt to catalogue the mutant-like variations 
that have been recorded among insects and other 
animals. The great work of Bateson, Materials 
for the Study of Variation 3 is full of instances, 
and the entomological and conchological jour¬ 
nals are full of many more. Everywhere we find, 
along with the universal quantitative variation, 
cases of qualitative, discontinuous variation in¬ 
volving entire unit characters; and these new 
characters are, probably, judging from our expe¬ 
rience with domesticated animals, inheritable. 


When we study a group of domesticated or¬ 
ganisms, such as poultry, we find the races dis¬ 
tinguished by characters that do not intergrade 



and can not be made to intergrade by crossing. 
An instance will show how these characters be¬ 
have. When a black fowl is crossed with an 
albino, of the Silky race, the offspring are black 
with a trace of red in the males. When the hy¬ 
brids are mated together they yield albinos, solid 
blacks, blacks marked with red, and typically 
colored red-and-black Games. If you keep on 
crossing together the red-ticked blacks you 
always get albinos, solid blacks, red-ticked blacks 
and Games, and nothing else. Such an experi¬ 
ence makes clear, better than any argument, the 
meaning of unit character, discontinuity, and mu¬ 
tation. Further analysis of this case shows that 
the black fowl has a unit character—melanic 
super-pigmentation—that has been added to the 
primitive Game coloration; and the albino lacks 
a unit character—the pigment forming enzyme 
—found in the ancestral plumage. Neither of 
these unit characters blends in the crossing. If 
now these unit characters of normal plumage 
color, excessive melanism, and albinism are to¬ 
day non-blending, essentially unalterable char¬ 
acters, it is probable that they have always been 
so and were so in their origin. But we have 
direct evidence as to this matter. In discussing 
the case of the black-shouldered peacock, Darwin 
concludes: “ The case is the most remarkable 
one ever recorded of the abrupt appearance of 
a new form.” If the black peacock arose sud¬ 
denly, so probably did the first black Mediterra- 



nean fowl, at a time long before records were 
kept. Again we find that human albinos appear 
suddenly, complete, and breed true like real spe¬ 
cies. We have other cases of semi-albinos of 
which the history is known. The blue-green 
Australian parakeets were first brought to Eu¬ 
rope in 1831. In 1872 an expert records seeing 
a single yellow specimen, and by 1877 they had 
become relatively common in Germany, since 
they breed true, and now they may be found in 
most bird-stores of our cities. This yellow par¬ 
akeet has lost the power of forming black pig¬ 
ment, and the new character appeared suddenly 
and completely. There is every reason for be¬ 
lieving that the yellow canary w T as thus derived 
from the green canary, the white Java sparrow 
from the gray form, and the albino fowl from a 
pigmented ancestor. The sudden origin of color 
changes is generally admitted by breeders and 
field naturalists; and many more cases of sud¬ 
denly appearing characters might be cited, such 
as hornlessness in cattle, sheep, and goats; tail¬ 
lessness in cats, dogs, and poultry; hairlessness in 
horses, cows, and dogs; spinelessness and hair¬ 
lessness in vegetative organs and fruits; fascia- 
tion of the stem and pelorism of the leaves and 
petals of many plants, and extra digits in poul¬ 
try, swine, horses, and man. These are examples, 
merely, for since man first began to domesticate 
plants and animals hundreds of new characters 
have appeared suddenly and completely and ca- 



pable of vigorous transmission. The frequency 
of such mutations depends on the number of 
individuals studied. 

Now, during the past four years I have bred, 
handled, and described over ten thousand poul¬ 
try of known ancestry. Of striking new char¬ 
acters I have observed many, some incompatible 
with normal existence; others in no way unfit¬ 
ting the individual for continued life. In the 
egg, unhatched, I have obtained Siamese twins, 
anteriorly duplex individuals with shortened 
upper jaw (like that of the niata cattle, pug 
dogs, and some carp), and chicks with thigh 
bones absent. There have been reared chicks 
with toes grown together by a web, without toe¬ 
nail or with two toe-nails on one toe; with five 
toes, six toes, seven toes, or three toes; with one 
wing lacking or both absent; with two pair of 
spurs; without oil-gland or tail (though from 
tailed ancestry) ; with neck nearly devoid of 
feathers; with cerebral hernia and a great crest; 
with feather shaft curved; with barbs twisted and 
dicotomously branched, or lacking altogether. 
Of the comb alone I have a score of forms: single, 
double, triple, quintuple, and walnut, V-shaped, 
cup-shaped, comprising two horns or four or six, 
absent posteriorly, absent anteriorly, and absent 
altogether. All of these conditions have been 
offered me without the least effort or conscious 
selection on my part, and each appeared in the 
first generation as well developed peculiarities, 



and in so far as their inheritance was witnessed 
each refused to blend when mated with a dissim¬ 
ilar form. For example, the pea X single gives a 
pea comb which in the next generation yields sin¬ 
gle and pea; cerebral hernia and no hernia give 
no hernia in the first generation, but hernia again 
in the second; taillessness may follow the Men- 
delian formula, polydactylism approaches it, and 
the color varieties illustrate it strikingly. In a 
word, while quantitative variations are never ab¬ 
sent in poultry, the sudden appearance and dis¬ 
appearance of full-fledged characters is most 
striking. Mutation as thus defined presents to 
the breeder as a common phenomenon. Fut, say 
the neo-Darwinists, your mutations are of a 
teratological sort and have nothing to do with 
species as we find them in nature. In reply I 
admit, first, that under domestication many mu¬ 
tations are preserved by man that would perish 
in nature. It is quite likely that mutations occur 
almost as frequently in nature as under domesti¬ 
cation, but the unfavorable new forms are apt 
to suffer early elimination. There remains, how¬ 
ever, a host of characters that are not detrimental 
to the individual, and such are not necessarily 
eliminated. They are teratological only in the 
sense that they are novel to the species, but they 
are of the same order as many of the specific dif¬ 
ferentia* of feral species. Take, for instance, the 
passerine birds—what are some of their striking 
qualitative characters? We find crossed bill 



(Loxia), crest (cardinal bird and jay), greatly 
elongated tail (widah bird), bare throat (bell 
bird), wattle (huia bird of New Zealand), barb¬ 
less feather shaft (paradise birds), barbs with¬ 
out barbules (emu-wren), twisted feathers (Chi- 
rocylla). The plumage may be glossy black, 
snowy white, or of broken colors. Since such 
characters have arisen suddenly, by mutation, 
in poultry it is fair to conclude that they have 
probably done so in other birds. Of course there 
are many characters found in wild birds that are 
not found in poultry, but where we have evidence 
that many characters have arisen suddenly, dis- 
continuously, it seems probable that many others, 
of the same general sort, whose origin can not 
possibly be known have arisen in the same way. 
The experimental demonstration of the mutative 
origin of many characters makes probable such 
an origin for characters beyond the pale of ex¬ 


There are many who are quite willing to admit 
that mutations do occur, but hold that the part 
they play must always be regarded as relatively 
less important than the summation of fluctua¬ 
tions. From this view the mutationist can ap¬ 
peal to the results of experiment. Does the 
breeder actually introduce new characters into 
the organic world by summating fluctuations? 
De Vries insists that the improvement that fol- 



lows selection nearly or wholly ceases after four 
or five generations, and if selection be abandoned 
the race rapidly returns to its primitive condi¬ 
tion. Such has been the experience of breeders 
of maize, sugar beets, and other crops, and of 
poultrymen who have sought to increase the egg 
yield of fowl. Permanent improvement, wher¬ 
ever made, has been effected either by hybridiza¬ 
tion with a wild form possessing the desired char¬ 
acter or by preserving a fortunate sport—a 
“ Shakespeare,” as Professor Hansen puts it. 
Such a sport is a new center from which further 
progress may start. Recognizing the futility of 
selecting merely those individuals having the old 
characters best developed, the most advanced 
breeders (as at Svalof in Sweden), have system¬ 
atized the search for single mutations in the 
midst of extensive seed plats. This law of im¬ 
provement holds for animals likewise. Four 
years ago I started several series of experiments 
to create, in poultry, new breeds by quantitative 
selection. In one of these I sought to re-create 
a uniform huff bird like the buffs that arose in 
China two thousand years ago and are the par¬ 
ents of all known uniformly red or buff breeds. 
A bird with a red-and-black plumage coloration 
of the Jungle fowl was crossed with a White 
Leghorn. The hybrids were white with red on 
the wings and breast. I then planned to breed 
together the reddest of these birds and the red¬ 
dest of their descendants until I should have 



gained uniformly red birds. The second genera¬ 
tion of the hybrids did show more red than the 
first, hut during the last two years no advance 
has been made. Again, a cock having a high 
single comb was crossed with a hen having a typ¬ 
ical low pea comb; the hybrid offspring had high 
combs with papillse placed high up on each side. 
An effort to establish by quantitative selection 
a high pea comb has failed. Dr. Castle tells me 
that his continued attempts to modify color types 
of rats by quantitative selection have of late been 
inefficacious, since regression is very strong to¬ 
ward the original types. The evolution of the 
American trotter is often cited as a clear case of 
the results of quantitative selection. Yet is it 
not true that the advances in recent years have 
been quite as much determined by the evolution 
of the sulky and certain technical improvements 
in handling the trotter and training him? The 
running record, the result of a larger selection, 
has, I understand, stood quite still for the last 
twenty years. Thus even race horses form no 
exception to the rule that selection, within given 
characters, soon reaches a period, and improve¬ 
ment must wait on the appearance of a new char¬ 
acter by mutation. 

This conclusion, far from being opposed to 
Darwin, would doubtless have been cordially ac¬ 
cepted by him, as certain passages in his writings 
indicate. 1 After describing the early improve¬ 
ment of the gooseberry, he says:— 

1 Compare the instance given at p. 48. 



“ The ‘ London ’ gooseberry (which, in 1852, had al¬ 
together gained 333 prizes) has, up to the present year 
of 1875, never reached a greater weight than that at¬ 
tained in 1852. Perhaps the fruit of the gooseberry 
has now reached the greatest possible weight, unless, in 
the course of time, some new and distinct variety shall 

De Vries could not have put it better. 


But, it is objected, the origin of characters by 
mutation can not account for adaptation as well 
as quantitative selection; and adaptation is the 
preeminent fact in nature. There is no good 
reason for drawing such a contrast. For the 
theory of mutation is nowhere incompatible with 
that of Natural Selection; there may just as well 
be, there just as truly is, a selection among dis¬ 
continuous variations as among quantitative va¬ 
riations. In the modern classification of varia¬ 
tions selection has come to be associated with 
quantitative variations; but Darwin did not al¬ 
ways so associate it, as I have tried to show. Any 
variation, of any kind or degree, must stand the 
test of fitness to survive. If it can not meet the 
test it must be eliminated. In a field I had 300 
young fowl, of which twenty per cent were of 
mixed colors, and eighty per cent were either 
white or black. Twenty-four of these birds were 
killed by crows, and all the dead were either 
white or black excepting one spotted white and 
buff. The solid colors are mutants; being con - 



spicuous on the grass they were relatively unfit 
to survive, and so they were eliminated. Again 
the elevation of the tail feathers by the hen is 
essential to successful coupling with the male; 
but this is impossible in rumpless hens, and they 
must all be infertile except for an operation. 
The wingless cock could successfully couple only 
with bantam hens, as without wings he could not 
balance himself while treading larger hens. 
These examples suffice to show how unadaptive 
mutations tend quickly to be eliminated. On 
the other hand, the split spur, the extra toe, the 
varied forms of comb, the frizzled and silky 
forms of plumage, even the absence of the oil- 
gland seem, under the conditions of the poultry 
yard, to offer no important impediment to sur¬ 
vival and propagation. We may conclude, con¬ 
sequently, that selection will act on mutations as 
well as on graduated variations, eliminating the 
unfit and letting survive favorable mutations or 
such as are merely neutral. But, granted that 
the unfit mutations are eliminated, can such a 
case of close adaptation as is exhibited by the 
leaf butterflies (Kallima and the rest) result from 
a series of mutations? Does not the very per¬ 
fection of the adaptation indicate that the final 
touches have been of the quantitative order? 
Not at all. The perfection of the result may be 
due to a combination of adaptive unit characters. 
Bateson, who examined thirty-eight individuals 
from one locality, finds that they fall into four 



discontinuous groups with respect to the colora¬ 
tion of the under side of the wings, a 3 “ leaf- 
veinings ” absent or nearly so, ground nearly 
plain; b } ground without veins but with promi¬ 
nent black speckled spots; c , veins strong, no 
blotches; d, with blotches, with or without veins. 
Here at least three unit characters appear; dark 
lines (veins), black speckled spots, and blotches; 
but one or all may be absent from a given wing. 
Between presence and absence of the character 
no intergrades occur except possibly in the case 
of “ nearlv absent ” veins. There is reason for 
concluding that even in Kallima new characters 
arise fully formed, and that these are numerous 
enough to affect all the detail of the pattern. If 
the combination of pattern characters is pro¬ 
tective, no doubt it will preserve many individ¬ 
uals from elimination. 

There is, moreover, still another way in which 
mutations may become adaptive; and that is by 
their possessor selecting a habitat that tits its 
organization. At the risk of encroaching on the 
subject of adaptation, assigned to another, I may 
give an illustration. The whole surface of the 
earth is scattered over with spores and seeds of 
plants and the resistant eggs and gemmules of 
various lower animals. Only if conditions are 
propitious will they hatch or germinate. Some 
years ago a dam broke at Cold Spring Harbor 
in February and drained a lake of eighty years’ 
standing. In the Spring a luxurious terrestial 



vegetation sprang up on the lake bottom from 
seeds lying dormant there. One Winter a ditch 
was dug through a salt marsh, where the only 
higher plant was a species of marsh grass— 
Spartina. The black peat cut from the ditch 
was piled in a ridge by its side so high that it was 
no longer covered by the tide. In the Spring 
various roadside weeds sprang up along the 
ridges, forming striking lines of vegetation run¬ 
ning athwart the marsh. In these cases the 
germs were present, but failed to germinate until 
conditions suitable to their organization inter¬ 
vened. So, in general, there are abundant means 
of dissemination, and for almost every character 
there is a situation for which it is best suited. In 
that situation the new character will prove itself 
adapted to its environment. 


The notion of mutation, when fully grasped, 
solves two difficulties which formerly confronted 
evolutionists. The first difficulty is the swamp¬ 
ing effect of intercrossing. If the usual result 
of crossing a new character with its absence were 
a blend of the two conditions, then the difficulty 
would be a real one. But even in wild species 
any unit character typically fails to blend when 
crossed with its absence. The unit characters of 
violets, shepherd’s purse, and spots of beetles are 
experimentally tested instances. The characters 



of domesticated organisms behave in the same 
way, as illustrated by poultry. Unit characters, 
then, in so far as they refuse to blend, will not 
be swamped by intercrossing, but will reappear 
intact in a predictable proportion in successive 

The second difficulty which the mutation doc¬ 
trine solves is discontinuity between species. 
Species differ in the presence or absence of cer¬ 
tain unit characters. These unit characters are 
typically discontinuous in their origin. Hence 
it is futile to look for intergrades; as well might 
one look for intergrades between carbon monox¬ 
ide and carbon dioxide. Species are discontin¬ 
uous because specific characters are discontin¬ 
uous; and specific characters, in so far as they are 
unit characters, are discontinuous because the 
molecular changes upon which they depend are 

It is rash at the threshold of any new science 
to accept any one hypothesis to the exclusion of 
others. The president of our Association has 
taught us our duty toward multiple hypotheses. 
As in the newer chemistry transitions between 
molecules are becoming a recognized possibility, 
so it can not he denied that some unit characters 
may arise gradually; or, as a result of repeated 
crossing, show true blending and intergrading 
conditions. Many characters are indeed less or 
more because they have an ontogeny, and the 
adults stop at different points in the ontogeny. 



as seems to be the case with human hair color. 
In many instances of geographic variation a gra¬ 
dation of climatic conditions causes a gradation 
in the development of a unit character all the 
way from invisibility to strong expression. 
Doubtless many important discoveries are about 
to be made in the field of graduated characters. 
But from henceforth we must, I think, start in 
our studies of unit characters from the stand¬ 
point of their normal discontinuity. While we 
remember the services of De Vries in insisting 
on the normal discontinuity of unit characters, 
we shall, in considering the idea of the unit char¬ 
acter, recognize more clearly how great is the 
debt of biological science to the insight of Charles 




The chief object in the life of any animal is 
to leave another like it in its place when it dies. 
To this end we find numerous adjustments and 
compromises, adaptations in animals or plants, 
to place them in harmony with the elements of 
their physical or biological environment, or to 
coordinate the different parts of the same animal 
or plant. 

We have major adaptations, such as those of 
birds, mammals, etc., for aerial respiration, and 
those of fishes for aquatic. We have also minor 
adaptations for a particular combination of tem¬ 
perature, light, heat, and the other elements of 
the physical environment. And, finally, we have 
adaptations fitting the animal to cope with other 
animals for a mate and a home, to secure food 
and to avoid being food. 

Aside from adaptations an organism consists 
of vestiges, and frequently of other characters, 
that are not adaptations. 

Vestiges, we know, are the remnants of past 
adaptations. Specific characters which are not 




vestiges and are not now adaptations may also 
be past adaptations, or possibly they may be¬ 
come such in the future; it is only certain that 
they now do not particularly fit the species for 
survival. Some characters, while undoubtedly 
adaptive, give the impression that they are over¬ 
done. The antlers of the deer, the fang of the 
saber-tooth, the power of continuous growth of 
the incisors of rodents, are all adaptations that 
have in some instances proved to be too much of 
a good thing. 


In the words of Weismann, the most ardent of 
the Darwinians, “ Adaptations arise whenever 
needed if they are at all possible.” 

Adaptations have usually been looked upon 
as adjustments in the organism to its environ¬ 
ment. The suggestion has more recently been 
made that adapted environments and habits are 
selected by animals adjusted to them. 

Is a man healthy and strong because he prac¬ 
tises athletics, or is he practising athletics because 
his strength inclines him to athletic sports? We 
have all been modified by our environment and 
by our activities. It is at least suggestive that 
some of us have never taken to pole-vaulting and 
should not have made a record if we had. Evi¬ 
dently there is a difference between the questions 
of the origin of adaptations in the individual and 
the origin of an adapted fauna. 



The latter is a comparatively simple question. 
No one, for a moment, would claim that the 
entire fauna of any particular area of land, or 
river, or ocean arose where it resides,—became 
adapted in its present habitat. Adapted faunas 
are only in small part autochthonous; in large 
part they are made up by selective migration. 


For a consideration of the origin of adapted 
faunas I would invite attention to the fresh water 
and cave fish-faunas. 

The major conditions distinguishing fresh 
waters from the ocean as an environment for 
fishes are these: (1) The fresh water contains a 
very much smaller per cent of salts in solution 
than sea water. (2) It is, with few exceptions, 
in continuous locomotion in one direction. (3) 
It contains sediment. Minor characters distin¬ 
guishing fresh water differ in different localities. 

Fresh-water fishes are not a group different 
from salt-water fishes. Many salt-water fishes 
can enter fresh water, and we may for present 
purposes assume that all candidates for fresh¬ 
water existence are adapted or readily adaptable 
to the fresh water. Adaptations to the second 
and third of the fresh-water conditions imply pe¬ 
culiarities in habit or structure not possessed by 
all fishes, and these must, in the main, have been 
acquired by the marine fishes before they could 
enter and maintain themselves in fresh water. 



The downward current and sediment, if the lat¬ 
ter is not too abundant, are not obstacles suf¬ 
ficient to keep an adult fish from entering fresh 
waters. The eggs and young furnish the point 
of attack. Among oceanic fishes we have many 
that have pelagic eggs, others that have adhesive 
eggs, others that have heavy cohesive eggs, others 
that have filaments for the attachment of eggs, 
while others harbor their eggs. 

Currents would naturally tend to carry pelagic 
eggs into the ocean, and as far as I know only 
one fish with pelagic eggs has succeeded in estab¬ 
lishing itself in fresh water, and it, the eel, to the 
present day, descends to the sea to deposit its 

The other types of eggs of marine fishes are 
all found in fresh waters, and it is certain that 
in many cases the possession of eggs of one or 
another of these sorts has enabled the fish to 
establish itself in fresh water. Thus the major 
adaptations were acquired by the ancestors of 
fresh-water fishes before they were eligible to a 
fresh-water existence. Innumerable minor adap¬ 
tations to the peculiar combinations of heat, sed¬ 
iment, light, etc., found in each selected locality, 
have no doubt arisen in such localities. 

When a new water area arises, selective migra¬ 
tion is the method of origin of the adapted fauna. 
The vast territory containing our North Amer¬ 
ican lakes and streams north of the southern line 
of glaciation, the area from the Arctic south to 



near the Ohio River, was covered a few thousand 
years ago with a sheet of ice. It contained no 
environment suitable for fishes. The entire 
fauna and flora of this area, including the fish- 
fauna, are composed of immigrants that moved 
in as the ice moved out, and selected the places 
adapted to each species. While a few of them 
have become modified since their advent into this 
area, their fundamental and even their minor 
adaptations were acquired elsewhere than in their 
present home. Their adaptation is due to the 
selection of an adapted environment. 1 The entire 
area is unsuitable as a place for the study of the 
origin of all but a few minor adaptations. 

The check by cold has not been placed on any 
individual migration or set limits to the adult. 
Rhiniclithys dulcis living in glacial waters and 
warm springs and the many species adapted to 
the great range of variation in the temperature 
in any of our temperate lakes show this. The 
temperature factor determining distribution is 
set rather by the adaptation of the eggs to warm 
or cold water. Our trout, salmon, and white 
fishes breed largely in winter when the tempera¬ 
ture is low. The rate of development of their 
eggs, like that of all cold-water eggs, is slow. 

1 Of the 152 species of fishes of the Great Lake basin, only 
26 species and varieties, 17 per cent of the total, are peculiar to 
the area. Five of these are but varieties of more southern species, 
and the other 21 more than represent the extent to which the 
fauna has become adapted in this area, for eight salmonids and 
eight cottids are cold water species that may have been crowded 
out of the region to the south of the basin, by the encroaching 
heat after the passing of the last glacial epoch. 



The warm-water species are warm-water species 
not because their individuals are incapable of 
entering cold water, for they do, but because 
their eggs will not develop in anything but water 
much warmer than that in which the eggs of cold- 
water species develop. Their eggs are quickly 
developed, they are adjusted to fluctuations in 
temperature, and they respond to such fluctua¬ 
tions in temperature by hastening or slowing 
their rate of development. 

The origin and modification of the cave fauna 
give a concrete example of the change of loca¬ 
tion resulting from predestined major adapta¬ 
tions and subsequent minor adjustments. Caves, 
at the present time, are being colonized by immi¬ 
gration of salamanders of the genus Spelerpes 
and other animals that have become adapted to 
a cave existence while living in the dark under 
rocks, bark, and in other similar places. The 
adaptation to the conditions of cave existence in 
this case determines the change of location when¬ 
ever a cave presents itself. 

That minor adaptations occur in these after 
they have become exclusively cave forms is shown 
by the structure of the permanent cave salaman¬ 
ders of Missouri and Texas. These have, in 
large measure, lost their color, and have degen¬ 
erate eyes. 

Not infrequently where we have extreme adap¬ 
tations to a particular and a peculiar environ¬ 
ment, such as are found in the blind fishes to the 



caves, or the ability of ichneumon flies to detect 
and lay their eggs in deeply hidden grubs, we do 
not really need to account for the extreme adap¬ 
tation to the extreme environment. The envi¬ 
ronment and the adaptation may have developed 
together, as armor-piercing projectiles and armor 
have so developed together. An illustration is 
found in the origin of the cave fishes of Ken¬ 
tucky, and still more of those of Cuba. 

The cave fauna of Kentucky, so highly 
adapted it would be hopelessly lost if removed 
from its peculiar environment, is the result of 
selective emigration, immigration, and local 
adaptation. It has become adjusted with the 
development of the environment it inhabits. At 
Horse Cave, Ky., a wide valley extends north 
and south. Tributary 
east and west. The hills bordering these valleys 
are limestone capped with sandstone. The 
north-and-south valley was formed by the Horse 
Cave River, which originally flowed over sand¬ 
stone like that capping the bordering hills. No 
doubt it had a fauna as varied as that of any 
surface stream. The stream first cut through 
the sandstone, then into the limestone, in which 
it gradually dissolved an underground channel. 
To-day not a sign can be seen on the surface of 
the streams that are responsible for the valleys 
about Horse Cave. At least one of them rushes 
through lofty chambers one hundred and eighty- 
five feet beneath the streets of Horse Cave. 

valleys come from the 



With this change in the environment, with the 
disappearance of Horse Cave River from the 
surface, its inhabitants were compelled to mi¬ 
grate. They moved in two directions to adapted 
environments. The shore-fishes, channel-fishes, 
etc., depending on light to find their food and 
mates, moved out to the Green River, where their 
descendants live to the present day. The fishes 
negatively heliotropic, nocturnal, or stereotropic, 
moved into the holes dissolved in the bottom of 
the river, followed its subterranean development, 
and their descendants live to-day in the stream 
which now flows entirely below the valley. They 
are colorless and all but eyeless, and have, no 
doubt, acquired this exaggerated adaptation to 
their present abode since their immigration. The 
major adaptation to the cave existence, the power 
of finding their food and mates without the use 
of light, they possessed before the formation of 
the caves, and it is responsible for their present 

Primarily blind fishes do not have degenerate 
eyes because they live in caves, but they live in 
caves because their ancestors were adjusted to do 
without the use of eyes. The degeneration and 
disappearance of their eyes form another matter. 

W herever in the past environments arose lack¬ 
ing light, they became, and still are, the gather¬ 
ing place of those not dependent upon light. 

The Cuban blind fishes offer another example 
of the concomitant development of a peculiar 



and complex environment and its peculiar fauna. 

The blind fishes of Cuba are members of a 

family of marine fishes, but live in fresh water in 

caves of central and western Cuba. They have 

undoubtedly arisen with the environment in which 

they now live. The caves are enlargements of 

rifts in coral reefs. They can be traced from 

the hills near Matanzas to the shore of Cuba. 

One of the cracks is seen in the naked coral beach 

near the Carboneria at the mouth of Matanzas 

Bay. Another can be traced a little way inland, 

but a few feet above sea level. The former must 

contain salt water—the latter certainly contains 

fresh water. In places similar to the former 

the nearest marine relatives of the cave blind 

fishes are found, with eyes. In the latter cave 

blind fishes are abundant. Evidently the ances- 


tors of the cave blind fishes have always lived in 
the crevices in which they now live. When these 
crevices were below the ocean’s surface they con¬ 
tained salt water. As the land arose the salt 
water was gradually replaced by fresh water, to 
which the fishes as gradually became adapted. 
The fishes have literally grown up with the 

Selective migration, the migration to adapted 
locations, is the chief factor contributing to the 
origin of adapted faunas. This factor change 
of location ” is to the origin of adapted faunas 
what the “ change of function ” is to the origin of 
adaptive structures. 




A. The Problem. The question of the ori¬ 
gin of the adaptations themselves is much more 
difficult. If comparatively few or no new adap¬ 
tations have arisen in any one neighborhood, 
nevertheless all these modifications must have 
arisen somewhere and should be accounted for. 
Many explanations have been offered. The sup¬ 
porters of some of the explanations adhere to 
them with the fanaticism of religious belief. But 
it is necessary to have been reared in the faith 
to see all that is claimed for them. 

Hereditary succession may follow a horizontal 
line or one that swerves up or down. In other 
words, successive generations may be alike, in 
which case the species remain in statu quo , or 
subsequent generations may deviate from their 
parents in one or more points. 

All deviations from the horizontal must start 
in the germ, or must become located in the germ. 
The question of the origin of adaptive deviations 
is the question of how and why adaptive ger¬ 
minal modifications arise, or how adaptive so¬ 
matic modifications are transferred to the germ. 
In either case it is the question of how the straight 
line of exact hereditary repetition may be caused 
to swerve in a definite direction to reach an 
adaptive point. This is the question of the pres¬ 
ent generation, perhaps of the entire twentieth 
century. ^ 



To be effective the deviation must be pre¬ 
served, but it is not necessary to enter into any 
discussion of Natural Selection. This very occa¬ 
sion bears evidence of the all but universal ac¬ 
ceptance of the principle. It forms part of 
nearly every theory of the origin of adaptation. 

B. The Material. In discussing the origin 
of adaptations I shall confine myself mostly to 
the brief examination of some of the adaptations 
in the American Characins, to determine, if pos¬ 
sible, to what extent different factors of evolu¬ 
tion have contributed to their origin. 

The Characins are fresh-water fishes now in 
their prime in tropical Africa and in tropical 

I hope I need not apologize for confining my¬ 
self to a bit of the wealth of that continent, 
South America, which has been the training 
ground of Darwin, Wallace, Bates, Muller, and 
so many of their supporters. 

In America there are known about six hun¬ 
dred species ranging from the borders of the 
United States to Patagonia. Different mem¬ 
bers are adapted to nearly all possible fish envi¬ 
ronments, both physical and biological. There 
are mud-eaters without teeth, flesh-eaters with 
teeth like a mowing-machine, and others with 
long fang-like canines projecting through the 
upper jaw when the mouth is closed. In the Es- 
sequibo River I caught over forty species in one 
day. Some of these minute translucent species 


A Few op tiie Numerous Types of Teeth in the Ciiaracins. 

(From photographs by the author.) 

1. Raphiodon vulpinus Spix. 

2. Astyanax bimaculatus brevoortii Gill. 

3. Serrasalmo humeralis Cuv. & Yal. 

4. Henochilus wheatlandi Garman. 

5. Acestrorhynchus falcatus Bloch. 

6. Hoplerytlirinus unitseniatus Spix. (Head resembles that of Amia.) 

7. Leporinus conirostris Steindachner. 

8. Prochilodus scrofa Steindachner. 

9. Aphiocharax dentatus Eigenmann & Kennedy. 


Some Similarities in the Characins. 

(All figures after Steindachner.) 

1. Luciocharax insculptus, a Garpike-like Characin. 

2. Salminus affinis, a Salmon-like Characin. 

3. Prochilodus longirostris, a Sucker-like Characin. 

4. Chalcinua magdalenae, a fresh water Herring-like Characin. 

5. Gasteropelecus maculatus, a flying Characin. 

6. Myleus knerii, a Pompano-like Characin. 

7 . Nannostomus unifasciatus, a Cyprinodont-like Characin. 



burrow in the sand in the bottom of the river, 
others fly with wing strokes through the air above 
the river, and others occupy all possible spaces 
between. In appearance they parallel our gar¬ 
fish, our pickerel, our top minnows, our pom- 
pano, our trout, our minnows, our suckers, our 
darters, our fresh-water herrings and shad; and 
besides these there are a variety of shapes and 
sizes and adaptations not to be found in other 
fishes. Chief of these is the series ending in a 
true flying fish, i.e. a fish with wing-like pecto¬ 
rals, large muscles to move them, and the ability 
to propel itself with wing strokes along the sur¬ 
face of the water for forty or more feet, and to 
continue its flight for five or more feet in the air. 

C. Causes of Adaptations. The causes lead¬ 
ing to new adaptations may be intrinsic or ex¬ 
trinsic. The theories of Nageli, Weismann, and, 
in part, of Darwin and De Vries, are based on 
intrinsic causes; those of Buff on, Lamarck, Gu- 
lick on extrinsic. 

D. Orthogenesis. Nageli, and in a modified 
form Eimer, Waagen, Osborn, Whitman, and 
others, have shown that lines of evolution are 
orthogenic, predetermined in definite directions. 
According to Nageli direction is maintained by 
the make-up of the protoplasm of the individual. 
According to Weismann direction is given by the 
process of germinal selection, helped out by per¬ 
sonal selection. By Osborn and others it is recog¬ 
nized but not explained. 



The Characins offer us the very best imagi¬ 
nable proof, both for orthogenesis and against its 
universality. The fact that lines of evolution 
radiate in so many directions in this family is ab¬ 
solutely conclusive proof that there are many 
possibilities, that evolution to adaptive points 
may not only take place along one line or par¬ 
allel lines, but along very many diverging lines. 
On the other hand, the fact that there are lines 
with but few breaks leading from the general¬ 
ized central type to such aberrant forms as the 
minute sand-burrowing Characins, duplicating 
our sand darters, or to the death-dealing Serra- 
salmo, or the flying Gasteropelecus, shows that, a 
path of adaptive modification once entered upon 
by these fishes, evolution along that line may 
take place, even beyond the point of highest ad¬ 
vantage. These lines are not parallel and can 
not therefore have been the result of the inherent 
make-up of the family. 1 They have in some way 
been determined and are being followed to the 

E. Mutations. The possibility of divergence 
in many directions has been experimentally 
demonstrated by X3e Vries, who, with others, has 
claimed that the line of adaptive modification is 
broken, not bent. Waiving the question of 
whether the difference between the bend and 
break is one of kind or degree, permit me again 

1 Similar characters like a pair of canines or ctenoid scales 
have appeared in very diverse genera both in Africa and in 
South America. 



to point out instances of both in the Characins. 
I do this fully aware of the fact that some of our 
experimentalists have claimed that evidence in 

the sys¬ 
tematic zoologist. It is, however, quite certain 
that evidence for mutation can not be obtained 
by experiment only. I have several times found 
evidence in favor of it in the Characins. 

In the Tetragonopterinse there are parallel 
genera or subgenera, as we care to look at them. 
One series has a complete lateral line; the other 
series has pores developed on but a few scales. 
No doubt one has been derived from the other— 
not once but several times. One species, Hemi- 
grammus inconstans, is evidently mutating. 
Two of the four specimens known have a com¬ 
plete lateral line, in the others it is quite short. 

Among hundreds of specimens of another spe¬ 
cies with an incomplete lateral line a single mu¬ 
tation has been found with a complete line. 
Moenkhausia australe by mutation is producing, 
or has produced Hemigrammus. In such cases 
we have, if a bull is permitted, individuals that 
are specifically alike but generically different. 

While we have many undoubted cases of muta¬ 
tion, there are many reasons why we should not 
jump to the conclusion that all adaptations have 
so arisen. 

One example of continuous variation leading 
to an adaptive point is found in some localities 
of Nicaragua. Here the species of Astyanaw 

favor of mutation would not be noted by 



czneus, elsewhere with two maxillary teeth, is 
varying in the old-fashioned way towards a form 
whose entire maxillary is covered with teeth, i.e. 
it is varying to become a Hemibrycon. Of 
thirty-five specimens there are nine with two 
teeth, two with three teeth, five with four teeth, 
five with five teeth, five with six teeth, five with 
seven teeth, three with eight teeth, and one with 
nine teeth in the maxillary. No doubt there are 
some who will claim that these are really muta¬ 
tions, not variations, and I am perfectly willing 
that they should put this balm upon their preju¬ 

The nature of the progressive degeneration of 
the eyes of blind fishes argues also against the uni¬ 
versality of the origin of adaptations by muta¬ 
tion. The degeneration of the eyes of such fishes 
is a continuous process. The eyes of individuals 
during their lifetime undergo a continuous de¬ 
generative modification leading sometimes to the 
entire elimination of the eye in the old. The 
retrogressive changes begin in ever earlier stages 
of the ontogeny. The differences between indi¬ 
viduals are so slight as to exclude the possibility 
of personal selection, without which either muta¬ 
tion or Natural Selection is incapable of produc¬ 
ing results. 

There is no evidence that mutation has had 
any more to do with the production of degener¬ 
ate eyes than special creation, and we can not 
even imagine how the degenerate eyes might have 



arisen by mutation. Their degeneration is due 
to orthogenesis or to use-transmission. 

F. Environmental Adaptation May Be 
Intrinsic or Extrinsic. 1 . Geographical va¬ 
riation or divergence. The facts of geographical 
distribution make it certain that adaptations 
have not arisen through intrinsic causes only. 1 
In fact, they make us doubt at times whether 
intrinsic causes have had anything whatever to 
do with the origin of adaptations. If all forms 
were the result of mutation, due to intrinsic 
causes, there is no reason why a large river such 
as the Rio San Francisco should not contain all 
the modifications possible to the genera inhabit¬ 
ing it, for Shull has shown that new forms may 
arise in a restricted area. But it does not. Of 
equal sized streams belonging to different sized 
river systems the one belonging to the larger sys¬ 
tem harbors a larger number of species of any 
genus. 2 And other things equal, the wider the 
distribution of any genus the more species com- 

1 Tower: Evolution in Chrysomelid Beetles, p. 314, says: “. . . All 
evidence showing them (mutants) to be most rigorously extermi¬ 
nated by natural selection. On the other hand, the study of geo¬ 
graphical distribution and variation gives the strongest of 
circumstantial evidences for direct and rapid transformation in 
response to environmental stimuli as to the result of dispersion 
. . . according to the method of trial and error, with 
natural selection acting as the conservator of the race by limiting 
the variation to a narrow range of possibilities.” 

2 Bean Blossom Creek of Monroe County, Indiana, draining an 
area of about 250 square miles, is known to harbor in two miles 
of its course 44 species of fishes. The Colorado, draining an area 
nearly 1,000 times as large, contains but 33 species of fishes. But 
Bean Blossom is part of the Mississippi basin that far exceeds 
the Colorado basin in size and harbors at least 200 species. The 
still larger Amazon basin harbors at least 700 species. 



pose it. In nearly all cases where a species is 
distributed over a wide, discontinuous unit of 
environment, i.e. an area broken up into isolated 
parts, the parts contain forms that are meas¬ 
urably different from each other. 

A most instructive example is furnished by 
the Characins. Astyanax fasciatus is found 
from Patagonia to Mexico, except at Panama 
and the Rio Parahyba. It differs in different 
localities, and in the Rio Parahyba, near Rio de 
Janeiro, and at Panama the differences have be¬ 
come of specific value. The species is continued 
in southern Mexico as Astyanax ceneus, and in 
northern Mexico as Astyanax argentatus . In 
other words, in those cases where the divergence 
has gone far enough we call the divergents spe¬ 
cies, in those cases where they are diverging, vari¬ 
eties. These geographical varieties are species 
in the making, just as truly as the elementary 
species of De Vries. 1 

Isolation is not always accompanied by differ¬ 
entiation. Some species of Galaxias in Patago¬ 
nia and Australia are identical, while those in 
different parts of Patagonia are different. Geo¬ 
graphical isolation must lead to differentiation 
if the isolation forces the individuals to live in 
places on the whole different from their original 
home. A species ( Astyanax fasciatus) may be 
all but identical even if isolated in different rivers 

1 The different diverging lines will be fully considered in my 
monograph on the Characins, now in preparation. 



from Mexico to Patagonia, provided it may oc¬ 
cupy the same sort of environment in each 
stream. There is more environmental differ¬ 
ence in the different parts of a cross-section of a 
river in the Amazon region, or in a mile of the 
length of a small brook, than there is in the 
pelagic region of streams from Mexico to Pata¬ 

2. Geographical convergence . Each river is 
made up of many different units of environment. 
The pelagic area is but one of these. Muddy 
bottom, weedy bottom, stagnant water, swiftly 
flowing water, are other units. Each has its 
peculiarly adapted fauna. Different members 
of the same family may belong to different eco¬ 
logical series, and different ecological groups are 
made up of members of different families. In 
shallow, swift water over gravel, in a small 
stream, the adaptations required are a heavy 
body, strong pectorals and ventrals, on which the 
fish sits and which are held in readiness for sud¬ 
den springs. The conditions and adaptations 
are the same whether the stream be in North 
America, in Cuba, or in South America. Fishes 
are adapted to the conditions in each locality, but 
the adapted faunas in the three areas are not re¬ 
lated. In North America, darters, or diminu¬ 
tive perches, are adapted to this niche; in Cuba 
it is members of the marine Gobies, and in South 
America members of the versatile Characins and 
catfishes. Shape and many other things count 



for little among fishes. All shapes occur at 
nearly all times and nearly all places. 

Similarly, blind fishes adapted to caves or 
other dark places have arisen in many places, but 
are not necessarily related to each other. The 
blind fishes of Point Loma are Gobies, and have 
their nearest relatives in neighboring waters. 
Those of the Mississippi valley belong to the 
Amblyopsidge, some of which live in the terranean 
streams of that valley. The caves of Cuba de¬ 
rived their blind fishes from the cracks of the 
coral reefs in which caves were formed. In 
South America their nearest relatives are the 
nocturnal catfishes of Brazil and the blind fishes 
of Pennsylvania have their nearest relatives in 
the nocturnal catfishes of Pennsylvania. 

The burrowing lizards of Florida living as 
earthworms do, look so much like earthworms 
that the very chickens do not discriminate against 

3. Geological convergence or 'parallelism . Geo¬ 
logical records of the simultaneous and similar 
changes in the form in the mass of species of any 
area during changing physical conditions are not 
wanting. For instance, Scott says:— 

“ The steps of modernization, which may be observed 
in following out the history of many different groups 
of mammals, are seen to keep curiously parallel, as may 
be noticed, for example, in the series of skulls figured by 
Kowalevsky, where we find similar changes occurring in 
such families as the pigs, deer, antelopes, horses, ele- 



phants, etc. Indeed, one may speak with propriety of a 
Puerco, or Wasatch, or White River type of skull, which 
will be found exemplified in widely separate orders.” 

One adaptation has not arisen once but many 
times. 1 To repeat, 44 Adaptations arise when¬ 
ever needed, if they are at all possible.” 

4. Origin of geographical and geological di¬ 
vergence and convergence . All these facts tend 
to show that adaptations have arisen as the result 
of the peculiarity of the environment. How? 

It has been demonstrated many times that the 
individual is modified by his physical environ¬ 
ment. It is claimed on the one hand that the 
deviation is maintained by its transmission to the 
germ-plasm, and thus the next generation; and, 
on the other, that the environment, in some cases 
at least, directly affects the germ-plasm. 

There is a third possibility. In some localities 
the individuals of certain species are very dark, 
in others they are practically without color. If 
the latter individuals are examined closely it is 
found that they are abundantly supplied with 
chromatophores, and only the needed environ¬ 
mental stimulus is lacking to bring out the strong 
color. This is not a matter of the simple expan¬ 
sion or contraction of the pigment, which may 
take place in a few moments, but the develop- 

1 Among characters that have appeared several times inde¬ 
pendently in the Characins may be mentioned: The incomplete 
lateral line, the scaled caudal, three series of teeth in the pre¬ 
maxillary, a pair of canines in the lower jaw, ctenoid scales, 
incisor-like teeth. 



ment of an excess of color under the necessary 

It is possible that other nascent intrinsic adap¬ 
tations are present in different individuals, unno¬ 
ticed and inconspicuous until the requisite envi¬ 
ronment causes them to reach the limit of their 
individual power, that they are environmental 
adaptations only in appearance. On the other 
hand, it is certain that in cave animals there is a 
gradual bleaching with the removal from the 
light. It is at first purely ontogenic. But no 
scheme of selection 1 will account for the pro¬ 
gressive reduction in the pigment in successive 
generations. Nevertheless the color becomes less 
in each generation. And in the final establish¬ 
ment of the bleached condition in hereditary suc¬ 
cession even in the light we have an instance of 
the transmission of an environmental adaptation. 

Where environmental adaptation is the result 
of a struggle with the physical environment, the 
struggle is entirely independent of the rate of re¬ 
production. The individual must adapt himself 
to heat and cold whether alone or not. Temper¬ 
ature and other elements of the physical environ¬ 
ment affect many individuals at one and the same 
time. For this reason the physical environment, 
when it makes its presence felt, operates in a 
dramatic way. It attacks the mass, sometimes 
killing thousands of the non-adapted at one 
stroke. As long as it does not kill all, the kill- 

1 Mutation is ruled out without selection. 



ing must be selective and preserve both those 
ontogenetically and those innately adapted. The 
attack being on the mass of species and individ¬ 
uals, it tends to preserve those that are alike . 1 

G. Functional Adaptations. The whales 
living like sharks look like them. Osborn re¬ 
marks: “ If a primate begins to imitate the hab¬ 
its of an ungulate by becoming herbivorous, it 
also begins to acquire the dental cusps of an un¬ 
gulate in about the same order as these cusps 
would arise in an ungulate.” 

I could paraphrase Osborn’s words for the 
Characins many times. , The Characins have 
taken on the habits of many fishes and have par¬ 
alleled them while they diverged from each other. 
A certain habit and habitat in fishes carries with 
it a certain regulative adaptation. Living as a 
sand-darter does, carries with it a sand-darter 
shape. The question that confronts us first is 
not, why does the sand-darter habit carry with it 
a certain form, but what caused Characins to 
adopt the darter habit? 

What caused Osborn’s primate to begin to imi¬ 
tate the habits of an ungulate? What caused 
different Characins to begin to eat mud, crusta¬ 
ceans, plants, plankton, and each other? 

Overproduction of individuals leading to 
crowding, the struggle with the biological envi¬ 
ronment for food (or light in the case of plants), 

1 No more striking example is found than in the old but uniform 
deciduous habit of plants of the temperate region. 



causes all accessible places to become inhabited. 
Food itself is dependent on other food, and this 
ultimately on light, heat, depth, nature of bot¬ 
tom, current, and other elements of the physical 
environment. The habitat once selected, the 
effect of the changed physical environment will 
cause the changes already discussed, and the 
changed biological environment will cause an 
animal to adopt a changed mode of existence. 

It is again possible either that innate charac¬ 
ters in certain individuals of a crowded com¬ 
munity cause them to migrate in certain direc¬ 
tions, or that chance individuals migrate, and that 
intrinsic or accidental extrinsic causes then start 
new activities. It is certain that new activities 
once adopted the result is individual modifica¬ 
tions . 1 It has long been claimed and as vigor¬ 
ously denied that these adaptive individual devia¬ 
tions are transmitted. 

The factors of both Buffon and Lamarck 
hinge on the possibility that somatic modifica¬ 
tions are transmissible to the reproductive cells. 
We have not been able to imagine how somatic 
changes could so influence the reproductive cells 
that they could, in their turn, produce individuals 

1 We can imagine that this process of overproduction and con¬ 
sequent adoption of different areas may take place in a small 
basin, but certainly the larger the basin the greater the diversity 
of conditions, the greater chance of comparative isolation in dif¬ 
ferent sorts of environments, and the greater the number of 

No small stream long isolated contains many species of a given 
genus. Notable exceptions are Orestias in Lake Titicaca, and 
Chirostoma in the Lerma. What applies to the species of a genus 
applies with equal force to the genera of a family. 



possessing in a measure the same characters. 
Nevertheless, the transmission of individual en¬ 
vironmental adaptations has been established. 

No cases of the transmission of functional 
adaptations as unquestionable as those of envi¬ 
ronmental adaptations are on record. 

It has seemed difficult indeed to devise experi¬ 
ments which would prove that the small somatic 
changes possible during a lifetime are transmit¬ 
ted. We were not sanguine enough to suppose 
that in one generation modifications could be 
effected and transmitted that would surpass nat¬ 
ural variability, and which could, therefore, be 
recognized as transmitted characters. I have 
long been convinced that the progressive degen¬ 
eration of the eyes of cave vertebrates, coupled 
with the differential degeneration of different 
parts, is due and can be due to nothing but the 
transmission of functional adaptation. I can 
not altogether regret that this evidence does not 
seem to have convinced many others. 

The possibility of the transmission of somatic 
characters to the reproductive cells has been 
shown by the transplantation of ovaries in chicks 
by Guthrie. He found that a black hen con¬ 
taining an ovary transplanted from a white hen, 
mated with a white male, did not give white 
chicks exclusively, as the non-transmissibility of 
somatic characters would require, but that more 
than half of the chicks were spotted with black. 
Also that a white hen containing an ovary trans- 



planted from a black hen and mated with a black 
male gave young all of which were spotted. 
These results, if based on rigorously selected 
material, ought to convince all but a packed 
jury that somatic characters are transmissible to 
the reproductive cells. If any one knows of de¬ 
fects in Guthrie’s material it is incumbent on him 
to furnish or define material free from all objec¬ 
tions on which his experiments may be repeated; 
for the method promises a final answer to this 
much debated question. 

H. Conclusions. We are forced to the in¬ 
evitable conclusions that adaptations are not 
chargeable to one factor, but that sometimes there 
has been one, sometimes another, and more fre¬ 
quently several factors have cooperated to bring 
about the adaptations in any one animal. 

It is but justice to Darwin to say that he did 
not pin his faith to the theory of Natural Selec¬ 
tion exclusively. Darwinism is broader than 
neo-Darwinism, whose insufficiency to account 
for all adaptations becomes daily more apparent. 

After fifty years of study of tbe origin of 
adaptations a single sentence from Darwin’s 
Origin of Species approaches closely to the gen¬ 
eral conclusions of to-day, and, “ lest we forget,” 
it should be emblazoned on the walls of every 
Biological Laboratory: “ These laws, taken in 
the largest sense, (are) growth, with reproduc¬ 
tion; inheritance, which is almost implied by re¬ 
production; variability, from the indirect and 



direct action of the external conditions of life, 
and from use and disuse; a rate of increase so 
high as to lead to a struggle for life, and as a 
consequence Natural Selection entailing diver¬ 
gence of characters and the extinction of less 
improved forms.” 

I. A Plea for the Naturalist. I can not 
close this paper without a plea for the naturalist 
and systematic zoologist. “ Analysis,” says Rus- 
kin, “is an abominable business. I am quite 
sure that people who work out subjects thor¬ 
oughly are disagreeable wretches. One only feels 
as one should when one doesn’t know much about 
the matter.” 

The systematic zoologist is liable to lose sight 
of the woods on account of the trees, and follow 
the example of Jean Paul Richter’s Quintus 
Fixlein, who collected a vast number of typo¬ 
graphical errors, assured the public that valuable 
conclusions could be drawn from them, and left 
it to some one to draw them. 

The imagination is in Biology as elsewhere the 
guiding spirit. The trouble is our imaginations 
are sometimes too heavily loaded with statistics 
and at other times they fly without the balancing 
kite’s tail of facts. The Paleontologists have 
contributed so much to speculative zoology be¬ 
cause their imaginations have been kept alive by 
bridging their numerous gaps and because they 
have not been hampered by too great a wealth 
of material. 



Whether we amputate eyes and legs to see 
them regenerate, determine the chromosomic dif¬ 
ferences between related species, centrifuge eggs, 
or invent new plants, potato beetles, guinea-pigs, 
or poultry, match butterflies, count scales, or 
measure fossils, we are all at work on the prob¬ 
lem of problems, “ The origin of adaptations.” 

Experiment is the watchword of the day; but 
while we are experimenting in our back yards we 
should not lose sight of the beauty and the impor¬ 
tance of the experiments in landscape gardening 
and zoological gardening, that are and have been 
going on in our front yards that extend from 
here to Cape Horn. 




On March 4, 1860, Charles Darwin wrote 1 to 
Joseph Leidy of Philadelphia:— 

“ Your note has pleased me more than you could 
readily believe ; for I have during a long time heard all 
good judges speak of your paleontological labours in 
terms of the highest respect. Most paleontologists 
(with some few good exceptions) entirely despise my 
work, consequently approbation from you has gratified 
me much; all the older geologists with the one exception 
of Lyell, whom I look at as a host in himself, are even 
more vehement against the modification of species than 
are even the paleontologists. I have, however, been 
equally surprised and pleased at finding that several of 
the younger geologists, who are now doing such good 
work in our own geological survey go with me and are 
as strong as I can be on the imperfections of geological 

“ Your sentence that you have some interesting facts 
6 in support of the doctrine of selection, which I shall 

1 Darwin’s letter to Dr. Leidy is under date of March 4, 1860, in 
reply, as he states, to Leidy’s letter of December 10, 1859. 

On March 27, 1860, upon the recommendation of Isaac C. Lea 
and Dr. Joseph Leidy, Darwin was elected a corresponding 
member of the Philadelphia Academy of Natural Sciences. It is 
probable that to the Philadelphia Academy belongs the honor of 
having been the first foreign society to accord this great work 
official recognition. This recognition was appreciated by Darwin, 
as is shown by his reference to it in a letter to Sir Charles Lyell, 
dated May 8, 1860. 

The original letter is in the collection of Dr. Joseph Leidy of 
Philadelphia, nephew of the great anatomist. 




report at a favourable opportunity,’ has delighted me 
even more than the rest of your note. I feel convinced 
that, though as long as I have strength I shall go on 
working on this subject, the sole way of getting my 
views partially accepted will be by sound workers show¬ 
ing that they partially accept them. I say 4 partially,’ 
for I have never for a moment doubted that, though 
I can not see my errors, much in my book will be proved 

Fifty years ago paleontology was an embry¬ 
onic science so far as natural philosophy is con¬ 
cerned; beyond the grand outlines of change in 
the world of extinct mammals and reptiles Dar¬ 
win knew little of its processes or results. In the 
letter cited above he is encouraged by Leidy’s 
promise of paleontological support for the gen¬ 
eral doctrine of evolution; he is even more grat¬ 
ified with the passage relating to Selection. In 
other words, in this characteristically candid let¬ 
ter Darwin appeals for evidence from paleontol¬ 
ogy in support of evolution; he hopes that sound 
workers will partially accept liis views regarding 
Selection; he does not for a moment doubt that 
much of his views regarding Selection will prove 
to be erroneous. 

A year later, April 2G, 1861, Darwin writes to 
L. Davidson, the great authority on bracliiopods, 
asking him to undertake a piece of work which 
would test the doctrine of evolution. 

44 . . .in that book [the Origin ] I have made the 
remark, which I apprehend will be universally admitted, 
that as a whole , the fauna of any formation is interme- 


diate in character between that of the formations above 
and below. But several really good judges have re¬ 
marked to me how desirable it would be that this should 
be exemplified and worked out in some detail and with 
some single group of beings. Now every one will 
admit that no one in the world could do this better 
than you with Brachiopods. The result might turn 
out very unfavourable to the views which I hold; if so, 
so much the better for those who are opposed to me. 

. . . I know it is highly probable that you may not 

have leisure, or not care for, or dislike the subject, but 
I trust to your kindness to forgive me for making this 
suggestion.” 1 

I shall show that the sanguine as well as the 
questioning prophecies of these epistles of 1860 
and of 1861 have been fulfilled to the very letter 
by paleontology; but in order to place the whole 
matter in its true perspective, and brighten rather 
than dim the grandeur of Darwin’s fame, let me 
first briefly picture paleontology as it was in 
1859 and as Darwin himself knew it even up to 
the time of his death in 1882. 

It is true that modern, or Darwinian, paleon¬ 
tology, as distinguished from the older, or Cuvie- 
rian paleontology, dates from a decade after the 
publication of the Origin, or from 1868, when 
Waagen 1 first exactly and minutely described 
the mutations which occur in a descent or phy- 
letic series of ammonites, and it is true that this 
epochal work was followed by others; so that the 

1 Life and Letters, II, pp. 366, 367. 

1 Waagen, Wilhelm Heinrich: “Die Formenreihe cles Ammonites 
subradiatus,” Benecke's Geognostische Palciontologische Beitrage , 

II, 1868, pp. 185-86. 



new paleontology of evolution, as distinguished 
from the old paleontology of special creation, 
reached vast proportions before Darwin’s death. 
But all this remained a terra incognita to Dar¬ 
win. Absorbed in his observations on living 
things, in his vast anthropological, psychological, 
zoological, and botanical researches in his revision 
of the Origin and other works, Darwin never 
found time or opportunity to grasp the meaning 
of the Darwinian paleontology. He attempted 
but failed to understand the work of Alpheus 
Hyatt, which was directly along the lines of that 
of Waagen, but unfortunately rendered unneces¬ 
sarily mysterious and difficult to comprehend 
through the inveterate American love of word¬ 
making. If Hyatt’s work had been expressed 
in Darwin’s simple language, as it might have 
been, then Darwin would certainly have grasped 
the Waagen principle of mutation, and we should 
have had the benefit of his marvelous insight into 
its significance. As it was, like Moses, Darwin 
led his paleontological followers to the Promised 
Land, but he did not live to enter it; he gave the 
impulse to search for phyla, or close continuous 
lines of descent of animals and plants, but he 
himself never observed a single phylum. 

Tliis simple fact is of vast importance in our 
estimate of the weight to be attached to Dar¬ 
win’s opinions. In contrast with Herbert Spen¬ 
cer he was essentially a deductive-inductive 
worker; that is, he pursued a trial hypothesis 



along the strictest lines of observation, he was 
less interested in how nature might, should, or 
would work than in how nature does work . Of 
his trial hypotheses that of adaptation through 
selection of minute favorable variations he can¬ 
didly tested by all the facts he could bring to¬ 
gether; among these, however, were none of the 
facts observable only in close phyletic series of 
fossils. This is a fair way to estimate Darwin 
and to be influenced by him, namely, by his strict 
inductive methods and in his times, not in ad¬ 
vance of his times. 

In the last half century thousands of fossil or¬ 
ganisms of all kinds have been exactly studied 
and compared, more or less complete descent 
series of vertebrates and invertebrates have been 
garnered, facts and principles entirely unknown 
to Darwin, and foreign to the logical mind of 
Huxley as well, have been revealed; in short, the 
data of induction as to how nature does work 
in the origin of certain new characters have to¬ 
tally changed in paleontology perhaps more than 
in any other biological field of observation. 

Two grand lines of observation have been fol¬ 
lowed in paleontology quite independently of 
each other: first, the minute changes in phyla of 
invertebrates observed in fossil shells by Waagen, 
Hyatt, Hilgendorf, Neumayr, and many others; 
second, minute changes in phyla of fossil mam¬ 
mals observed by Osborn, Scott, Deperet, Mat¬ 
thew, and many others. It is obvious that the 



hard shells of molluscs and the enameled teeth 
and other parts of mammals are entirely inde¬ 
pendent parts of entirely different organisms, 
and that if similar laws have been discovered in 
such widely distinct fields of observation they 
tend to show that these laws were of force or of 
wide potency in living organisms in general. 

We are, therefore, now enjoying an entirely 
new vintage of facts and principles. How far 
can this new wine be put into the old bottles of 
Darwin’s beliefs? What would Darwin him¬ 
self say if with Iris incomparable candor and his 
incomparable power of generalization he were 
to examine these facts discovered in close pliyletic 
series of vertebrates and invertebrates, and were 
to test the conclusions which appear to be in¬ 
ductively derived from them? 

Thus two great questions arise on this anni¬ 
versary day in connection with the two words, 
Darwin and Paleontology: first, what has Dar¬ 
win done for paleontology; second, what has pa¬ 
leontology done for Darwin or for the sum and 
detail of Darwin’s teachings? 


The former question is readily answered; as 
Cuvier was the first, so Darwin was the second 
founder of paleontology. His contributions to 
the principles of the science were prepared for 



by his familiarity through Lyell with the work 
of the great Frenchmen Buff on, Lamarck, and 
Cuvier. These principles were stimulated and 
made his own by his observations during the voy¬ 
age of the Beagle , and his survey of the extinct 
life of South America. His comments on what 
he saw exhibit a close observer of nature, the 
geologist and biologist, the ideal paleontologist 
except only in the technical field of anatomy. 
He himself knew few or no lines of descent, but 
he felt they must be found, and he set the whole 
world in search for them. These principles of 
paleontology were given full expression in the 
Origin of Species. There are in that great work 
innumerable allusions to what may now be called 
the working method of paleontology, the method 
which Huxley formulated and expressed in clear 
terms in 1880. Darwin believed that the breaks 
in the geological record caused the interruptions 
in the hypothetical phyla, and his fond confidence 
that they would be overcome has been more than 
vindicated. The impulse which he gave to ver¬ 
tebrate paleontology was immediate and un¬ 
bounded. It found expression especially in the 
writings of Huxley in England, of Gaudry in 
France, of Kowalevsky in Russia, of Cope and 
Marsh in America. These works swept aside 
the dry fossil lore which had been accumulating 
since the passing of Cuvier’s influence, and 
breathed the new spirit of search for the princi¬ 
ples of fitness, of descent, of survival, and of ex- 



tinction. Thus Darwin gave a new birth to pa¬ 
leontology, as to every other branch of biology. 

The second question, what has paleontology 
done for Darwin, calls not for one but for a series 
of answers. In some ways it has vastly strength¬ 
ened him as a natural philosopher or as the seeker 
of natural causes; it affords more convincing 
proof than any other branch of biology of the 
truth of Darwin’s grandest contribution to our 
knowledge of the universe, namely, his complete 
demonstration, which others had attempted and 
failed to give, of the law of evolution with all its 
consequences. In this way it has shown him to 
be quite infallible; in other ways it has under¬ 
mined his position and shown him quite as fallible 
as other great men. 

It seems therefore that the most important 
part which a paleontologist can play in this dis¬ 
cussion is to state exactly and clearly what pale¬ 
ontology has to say for and against the special 
hypotheses set forth by Darwin as well as what 
it has to say that is entirely new since Darwin’s 


Darwin’s own hypotheses of the causes of evo¬ 
lution through Natural Selection are concentric 
or in ever narrowing circles; they center around 
the broad survival of the best fitted groups of 
organisms of all degrees, of orders, families, 
genera, species, varieties, of the best fitted single 



organs, of the best fitted variations in these, and 
finally come down to the focal point that the 
causes of adaptation and the origin of species 
ultimately center around constant variability and 
the survival or selection of minute variations. 
From his exhaustive knowledge of Darwin’s 
work Professor Poulton holds that the great phi¬ 
losopher had in mind as the material for Natural 
Selection small variations , congenital and inher¬ 
itable; he knew well that the material included 
(C great and sudden variations ” but he did not 
believe that they were selected. His variations 
had no power of developing in definite direction. 
Direction was given by Selection. That is, it 
remained for selection to give direction by choos¬ 
ing from all variations those which happened to 
be in an adaptive direction. 

It is obvious that as we pass from the broad 
to the minute the theoretic demand upon the 
selection hypothesis becomes more and more in¬ 
tense, but the tendency of our time is to waive 
aside theoretic considerations and come down to 
actual observations and facts and see how far 
they support the Darwinian and other hypoth¬ 
eses, and how far they call for new hypotheses 
and interpretations. 

Thus the question of the hour is to see what 
parts of this entire hypothetical system of selec¬ 
tion within selection, until we reach the minute, 
are in accord with modern paleontological evi¬ 



Let us begin with the broad and proceed to 
the minute. 

Selection of entire animals and parts of ani¬ 
mals through elimination. Paleontology not 
only sustains Darwin’s broad induction of evolu¬ 
tion, but in an equally convincing manner it sus¬ 
tains his broad induction that Natural Selection 
is and always has been one of the dominant prin¬ 
ciples of change in the aspect of the living world. 
Because of the thousands of facts which he mar¬ 
shaled from every branch of natural history in 
support of this factor he is entitled to be regarded 
as the founder although not as the originator of 
the law of the survival of the fittest. In study¬ 
ing the causes of the extinction of the mammals 
throughout Cenozoic times , 1 I have been struck 
by the fact that there is hardly an hypothesis of 
extinction suggested by more recent research 
which escaped the more or less serious attention 
of Darwin. My general survey of the economy 
of extinction in this great class of animals cer¬ 
tainly establishes the existence of a very great 
variety of causes of elimination, some of which 
are internal, some external in origin, while all 
operate under the broad principle of selection. 
I believe I have found fresh proofs of the con¬ 
tinuous operation of selection on all organs , be¬ 
cause some new and brilliant instances in addi¬ 
tion to those gathered by Kowalevsky and Marsh 

1 “ The Causes of Extinction of Mammalia,” American 
Naturalist, Vol. XL, No. 479, December, 1906, pp. 769-95; No. 
480, November, 1906, pp. 829-59. 



are adduced not only in support of the broad in¬ 
duction that the fittest survive, but also in proof 
of the more specific principle of Darwin that cer¬ 
tain single organs , such as certain types of tooth 
structure, or of foot structure, have been favor¬ 
able or fatal to their possessors. This is now 
capable of statistical demonstration and no 
longer a matter of highly probable inference, as 
Darwin left it. The most readily comprehended 
case is that during the Upper Oligocene and 
Lower Miocene periods, a large number of en¬ 
tirely unrelated quadrupeds possessed a closely 
similar pattern 1 in their grinding teeth; it was 
the one character which they possessed in common 
and certainly was the one character which led 
them all alike to extinction. 

Selection of the larger variations of propor¬ 
tion . When we approach the further applica¬ 
tion of the selection principle, however, as more 
novel with Darwin and more intimately asso¬ 
ciated with his personal views, namely, his doc¬ 
trine of the selection of larger variations of pro¬ 
portion, as, for example, in the classic case of the 
elongation of the neck of the giraffe, we are 
forced to admit that paleontology neither posi¬ 
tively sustains nor destroys this working hypoth¬ 
esis, although the evidence which it presents is 
rather favorable than unfavorable. 

By exclusion of other hypotheses, paleontol- 

1 I allude to the grinding teeth technically known as bunosele- 
nodont, that is, with a rounded crown ( bunos) on the inner side of 
the grinders, and crescentic ( selene) ridges on the outer side. 



ogy may however be said to lend support to this 
hypothesis. Changes of proportion in long 
periods of time, that is, in millions of years, play 
an enormous part in evolution, as seen by the fol¬ 
lowing contrasts in certain well-known structures, 
among herbivorous quadrupeds:— 

Short-toothed and long-toothed=short-lived and long- 

Short-toothed and long-toothed=browsers and grazers. 
Short-footed and long-footed =short rangers and 
long rangers. 

Short-headed and long-headed ^browsers and grazers. 
Short-necked and long-necked =near feeders and far 

Among the horses these very changes of pro¬ 
portion in four important organs, the teeth, the 
feet, the head, and the neck, constitute a very 
large percentage of the total evolutionary 
changes, and result finally in certain phyla of 
horses becoming long-lived animals, capable of 
traveling long distances, capable of grazing on 
the harder kinds of food, and capable of reach¬ 
ing food at a considerable distance from the 
body. This joint action of heredity, ontogeny, 
environment, and selection of congenital varia¬ 
tions of proportion, appears to best explain the 
transformation of round-headed or brachyceph¬ 
alic into the long-headed or dolichocephalic forms 
of the horses as well as of other herbivora, in re¬ 
lation to the browsing or grazing habit respect¬ 
ively. The only explanation which has as yet 



been offered for such changes of proportion is 
that of the selection of hereditary quantitative 
variations . 1 

I am therefore myself inclined to regard long¬ 
headedness or short-headedness in the vertebrates 
generally as well as the similar phenomena of 
long-footedness (dolichopody) or short-footed- 
ness (brachypody) as in many cases caused by 
the selection of changes of proportion; yet I 
freely admit that we can not prove or demonstrate 
this Darwinian hypothesis through paleontology. 

One direct paleontological reason may, how¬ 
ever, be adduced in favor of the hypothesis of 
selection of variations of proportion, namely, 
changes of proportion do not fall under what I 
call the law of ancestral control of variation. 
Head proportions or foot proportions, or, in 
fact, any other change of proportion can not be 
regarded as controlled by ancestral affinity, be¬ 
cause descendants of the same ancestors soon give 
rise to very different results. For example, a 
primitive intermediate (or mesaticephalic) form 
of skull does not at all control the form of skull 
which may be derived from it; the animal is free, 
as it were, to evolve into one of many different 
kinds of head forms. The point is that hered¬ 
itary predetermination does not appear in the 
evolution of proportion and of form as I shall 
show that it does appear in the evolution of cer- 

1 The fact that this throws little light on the origin of dolicho- 
cephaly or brachycephaly in the human species appears to throw 
the selection hypothesis again into doubt. 



tain other new characters, except in so far as 
an evolutionary tendency once established in the 
direction of brachycephaly or dolichocephaly is 
apt to be pursued to its very limits or extremes. 

Selection of minute variations. Not only is 
paleontology not positively conclusive on the hy¬ 
pothesis of selection of large variations, it has 
nothing positive, but rather something negative 
to say on the still more intimate or focal feature 
of the Darwinian hypothesis that minute varia¬ 
tions without direction in certain specific organs 
are of survival or of elimination value. Certainly 
appeal must he made to some other branch of 
biology on this particular problem, if indeed it 
is ever capable either of verification or of dis¬ 
proof. Through paleontology we can neither 
say that Darwin was right or wrong, because we 
meet with certain peculiar barriers or limitations 
of paleontological observation. Slight changes 
of geological level may mark long periods of 
time. The limitations are not solely due to rela¬ 
tive rarity of contemporaneous or synchronous 
material, because among invertebrates vast num¬ 
bers of synchronous forms are sometimes brought 
together so that minute variations may be read- 

o *7 

iiy measured, but it is quite another matter to 
prove through paleontology that such variations 
are selected. It was Waagen’s view that it is 
not the variations but the less conspicuous muta¬ 
tions which reappear in the next generation. 
This question of the selection of minute varia- 


tions is probably par excellence a field of research 
for the biometrician and the experimentalist 
rather than for the paleontologist. 


We now reach a turning point and pass from 
differences of proportion, of development, and 
of degeneration, to the origin of new characters. 

Origin of new characters not by selection of 
the fit from the fortuitous . When, however, this 
focal point of the selection of minute variations 
is pressed home as an hypothesis of the origin of 
all new adaptive characters, then paleontology 
ceases to be either neutral, silent, or inconclusive, 
and gives to Darwinism a most emphatic nega¬ 
tive. In all the research since 1869 on the trans¬ 
formations observed in closely successive phyletic 
series no evidence whatever, to my knowledge, 
has been brought forward by any paleontologist, 
either of the vertebrated or invertebrated ani¬ 
mals, that the fit originates by selection from the 

Lest the statement be made that this is truly 
the sanctum sanctorum of Darwin’s theory of 
adaptation, let me recall the historical fact 1 that 
fitness for twenty-five centuries had been the 
stumbling block of those who sought a natural¬ 
istic interpretation of nature; that Kant 2 had 

1 Osborn, H. F.: From the Greeks to Darwin. An Outline of 
the Development of the Evolution Idea, Vol. 1 of the Columbia 
University Biological Series, 8vo, Macmillan, 3rd ed., p. 248. 

2 Ibid, p. 100. 



wondered if any one could ever give an explana¬ 
tion of the origin of fitness in a blade of grass; 
that fitness had become the teleological citadel of 
the supernaturalists. Darwin was believed by 
many, but not by all, to have solved this problem 
of the ages. Let me quote the very recent lan¬ 
guage of our most profound American philo¬ 
sophical thinker, William James 1 :— 

“ It is strange, considering how unanimously our 
ancestors felt the force of this argument [that is, the 
teleological], to see how little it counts for since the 
triumph of the Darwinian theory. Darwin opened our 
minds to the power of chance-happenings to bring forth 
4 fit ’ results, if only they have time to add themselves 
together. He showed the enormous waste of nature in 
producing results that get destroyed because of their 

I repeat: paleontology is not silent, but pre¬ 
sents a solid array of evidence against what was 
never more than an ingenious working hypoth¬ 
esis of Darwin; one he fathered and loved, it is 
true, but which met little favor in the sturdy and 
logical mind of Huxley, predisposed as he was 
to Darwinism. It is now no longer a question 

1 James, William: Pragmatism. 8vo, Longmans, Green & 
Co., New York, 1907, pp. 110, 111. Professor William Bateson 
gives a similar definition. “ Darwin’s Solution. Darwin, without 
suggesting causes of Variation, points out that since (1) Varia¬ 
tions occur—which they are known to do—and since (2) some 
of the Variations are in the direction of adaptation and others 
are not—which is a necessity—it will result from the conditions 
of the Struggle for Existence that those better adapted will on 
the whole persist and the less adapted will on the whole be lost.” 
Materials for the Study of Variation, Treated with Especial 
Regard to Discontinuity in the Origin of Species, 8vo, London, 
1894, p. 5. 



of logic but of fact. Does paleontology sup¬ 
port this focal hypothesis of fortuity or absence 
of direction in the minute variations leading to 
adaptation, or does it destroy it ? 

The answer is in no uncertain sound. While 
fortifying all the outworks, paleontology under¬ 
mines the hypothesis of adaptation through the 
selection of the directed from the variations with¬ 
out direction by eliminating the occurrence of the 
variations without direction in many important 
organs. Fortuitous variations as material for 
advance should certainly be found, if anywhere, 
in closely successive phyletic series; they have not 
been found. At the same time this evidence 
does not leave a vacuum, but replaces the law 
of chance by another law, namely, that as in the 
domain of inorganic nature, so in the domain of 
organic nature fortuity is wanting, and the fit 
originates in many hard parts of the body 
through laws which are in the main similar to 
growth,—laws the modes of which we see and 
measure, the causes of which we do not and may 
never understand, but nevertheless laws and not 
fortuities or chance happenings. 

Now let us inquire how it comes that paleon¬ 
tologists, far in advance of other biologists, have 
reached this profoundly important principle as 
to the origin of certain new characters. 

The paleontologist observes origins. Having 
already disclaimed certain powers for paleontol¬ 
ogy as regards evidence on the evolution factors, 


and having still others to disclaim, I may now 
claim for paleontology as its transcendent power 
that it alone of the biological sciences can pro¬ 
duce evidence of the reign of definiteness, of 
order, of law in the origin and early history of 
certain adaptive characters, because in the hard 
parts of animals it alone is in with organs before 
their beginnings and from their beginnings to 
their finalities. The beginning of new charac¬ 
ters is at once the central problem and the most 
mysterious problem of evolution. In using the 
word “ beginnings ” or “ origins ” we do not 
imply causes but simply appearances in order of 
time. It is of unique advantage to the paleon¬ 
tologist as an observer of the origin of new char¬ 
acters that concentrating his attention on single 
characters entirely irrespective of the species 
question, which is wholly a by-question, he may 
trace new characters from the period before their 
origin, through their first adumbrations, through 
the stages which may be denominated as origins, 
through their every subsequent change, through 
their entire history, in fact. In this long-lived 
sense as an observer the paleontologist is immor¬ 
tal in contrast with those mortal observers, the 
zoologists and experimentalists. 

Second, in successive series of animals such as 
horses, rhinoceroses, or the related titanotheres, 
the paleontologist may observe the behavior of a 
very large number of characters at the same time 
and through long periods of time, some rising, 



some falling, one structure taking a rounded 
form, the structure next it taking a crescentic 
form, every single element evolving independ¬ 
ently in some way. The theory of the simulta¬ 
neous operation of several factors on different 
groups of characters and on different kinds of 
group characters could only suggest itself to a 
paleontologist working on a very complex ani¬ 
mal like one of these big quadrupeds in which 
countless numbers of characters are simulta¬ 
neously evolving. 

Third, the paleontologist has this further 
unique advantage: he is in a position to judge 
which new characters are important and which 
are unimportant; he is, therefore, in a peculiarly 
favored judicial position. By contrast neither 
the zoologist nor the botanist is in a position to 
know whether a new character which he believes 
to be important is going to persist or not. The 
difficulty under which the zoologist labors in this 
lack of judicial discernment is illustrated, for 
instance, in Bateson’s Materials for the Study of 
Variation , in which he attempts to prove the law 
of discontinuity from a review of a very large 
assemblage of characters, the greater number of 
which the paleontologist would recognize at once 
as wholly unimportant and non-significant. The 
only way zoology and botany could overcome 
this disadvantage, as regards the origin of new 
characters, would be through a series of relay 
observations extended by successive observers 



over long periods of time or through a series of 
lifetimes. The mortality of the zoologist, the 
experimentalist, the botanist, is a fatal handicap, 
for the reason that they are alike too short-lived 
to observe and measure those changes in the hard 
parts (if they exist) which are so excessively slow 
as to be invisible and immeasurable by mortal 
eye; while the paleontologist alone is in a posi¬ 
tion to demonstrate the existence and importance 
of such slow origins. With his short-time vision 
is not the zoologist and botanist more prone to 
fall into the error of “ exclusive hypotheses,” and 
conclude that visible, measurable changes, such 
as saltations, discontinuities, mutations of De 
Vries are the most important if not the only 
changes which are going on in organisms? Thus 
the paleontologist listens serenely to the fanfare 
of trumpets of exclusive hypotheses; he knows 
that time and time alone will show whether these 
will with other fashions fade. 

Sudden origins demonstrable by zoology and 
botany , but not by paleontology . As regards 
the soft parts of animals and even as regards pro¬ 
portions, changes which occur geographically or 
in space can be measured by the zoologist, but 
this does not apply to origins. The first point 
as to origin, namely, the question of rate or speed 
of origin, finds paleontology at a disadvantage 
as a sphere of research. The law of sudden or 
discontinuous principles has repeatedly been 
demonstrated in zoology and in botany. It 



reaches the climax in De Vries’ work, where mu¬ 
tation is regarded as an exclusive principle, but 
discontinuity can never be either demonstrated 
or disproved by paleontology, since this is the 
most unfavorable of all the biological fields for 
the recognition of sudden changes of character, 
through absence of that abundance of synchro¬ 
nous and contemporaneous material for com¬ 
parison on which alone it is safe to establish the 
existence of a mutation. Despite this obvious 
shortcoming of paleontology, it is noteworthy 
that the saltatory hypothesis has been—illogically 
I believe—fathered by a series of paleontologists, 
by St. Hilaire in 1830, by Cope, and more re¬ 
cently by Dollo and Smith Woodward. It 
should be borne in mind constantly that wherever 
a new animal suddenly appears or a new char¬ 
acter suddenly arises in a fossil horizon, such ap¬ 
pearance may be attributable to the non-discovery 
of the greater or more minute transitional links 
with older forms or to the sudden migration of a 
new type provided with a new organ or organs 
which have gradually evolved elsewhere. More¬ 
over, the doctrine of sudden appearances is di¬ 
rectly the reverse of Waagen’s law of mutation. 
The point, however, is that as a sphere of evidence 
paleontology neither approves nor disproves the 
law of discontinuity. 

Slow origins demonstrable by paleontology , 
but not by botany or zoology. Paleontology, on 
the other hand, affords the most favored field for 



the observation of slow origins of new characters. 
It is well known that Darwin was a firm advo¬ 
cate of the hypothesis of slow origins; this was, 
indeed, consistent with his doctrine of evolution 
by the adding up of favorable fluctuations. The 
law of gradual appearance or origin of many new 
characters in definite or determinate directions 
from the very beginning I regard as the grandest 
contribution which paleontology has made to 
evolution. This law of gradual change in the 
origin and development of single characters, 
measurable only at long intervals of time, has 
now come to rest on a vast number of observa¬ 
tions; it is the working basis of the science. Ver¬ 
tebrate and invertebrate paleontologists search¬ 
ing independently of each other on wholly differ¬ 
ent kinds of animals have reached entirely sim¬ 
ilar opinions. 

Mutations of Waagen. The first, I believe, 
to express from observation the law of gradual 
change was Waagen in 1868. The mutations 
of TV aagen 1 were originally distinguished by 
him from the often more conspicuous contempo¬ 
rary fluctuations by the fact that, although seen in 
minute features, they are very constant and can 
always be recognized again, but only in success¬ 
ive geological levels, that is, at intervals of many 
geologic years. Such gradations are observed 

1 Waagen, Wilhelm Heinrich: “Die Formenreihe des Ammonites 
subradiatus,” Benecke's Geognostische Palaontologische Beitrdge , 
II, 1868, pp. 185-86. 



in single characters; they are the nuances , or 
shades of difference, which are the more gradual 
the more finely we dissect the geologic column; 
bit by bit the Waagen mutations are added to 
each other in different single characters until the 
sum or degree of mutations is reached which no 
zoologist would hesitate to assign specific or ge¬ 
neric rank. The essence of Waagen’s mutation 
is orthogenesis or variation in determinate direc¬ 
tions, as distinguished from the indefinite varia¬ 
tion implied in Darwin’s theory. 1 This law re¬ 
ceived the powerful support of our countryman 
Hyatt, of the Austrian paleontologist Neumayr, 
and many others. 

In 1889 Osborn, 2 in observing the teeth of large 
numbers of Eocene mammals, chiefly of the 
smaller monkeys, horses, tapirs, and other forms, 
first noticed that new elements here also arise def¬ 
initely and can only be measured after long in¬ 
tervals of time. He first applied (1890) the 
term “ definite variations ” 3 to these characters, 
but many years later, on observing that many 
such characters were destined to become adaptive, 
he gave the same elements the name “ rectigrada- 

1 Professor Poulton maintains that determinate variation is 
precisely what Natural Selection would show, namely direction 
through the accumulation of favorable variations. 

2 Osborn, H. F.: “The Paleontological Evidence for the Trans¬ 
mission of Acquired Characters,” British Association Reports, 
Newcastle-upon-Tyne meeting, September, 1889. London, 1890. 

3 “Are Acquired Variations Inherited? Opening a Discussion 
upon the Lamarckian Principle in Evolution.” American Society 
of Naturalists, Boston, December 31, 1890. American Naturalist, 
Vol. XXV, No. 291, March, 1891, pp. 191-216. 



tions.” 1 It appears probable, but it is not yet 
demonstrated, that the rectigradations of Osborn 
are of the same nature as the mutations of 
Waagen. Scott 2 in 1894 was the first vertebrate 
paleontologist to call the attention of his co¬ 
workers to Waagen’s law among the inverte¬ 
brates. This principle of rectigradiation in the 
origin of many new characters in the mammals 
cuts both ways; it demonstrates the absence of 
the chance happenings without direction , which 
form the basis of Darwin’s hypothesis of the 
origin of adaptations, and positively shows that 
certain new adaptive characters appear definitely 
and assume adaptive direction from their very 
minutest beginnings. 

To sum up, the law of gradual change in cer¬ 
tain determinate, definite, and at least in some 
cases adaptive directions, through very long 
periods of time, and the absence of chance or non¬ 
direction in the origin of a large number of 
adaptive and other new characters, is the com¬ 
mon working principle both in vertebrate and 
invertebrate paleontology. 

It is thus that the characters which the older 
paleontological observers, such as Owen, Leidy, 
Cope, and Marsh, designated as specific and even 
as generic are gradually built up. We thus wit- 

1 “ Homoplasy as a Law of Latent or Potential Homology,” 
American Naturalist, Vol. XXXVI, April, 1902, pp. 259- 

2 Scott, W. B.: “On Variations and Mutations,” American 
Journal of Science, Vol. XLVIII, 1894, pp. 355-74. 


ness the origin of what naturalists have been des¬ 
ignating as species. 

In a lower horizon a cusp of one of the teeth, 
for example, is adumbrated in shadowy form; in 
a slightly higher horizon it is visible; in a still 
higher horizon it is fully grown, and all paleon¬ 
tologists have hitherto agreed to honor this final 
stage by assigning to the animal which bears it 
a new specific name. In the face of these con¬ 
tinuous series of changes revealed by paleontol¬ 
ogy the species and genera of Linnaeus break up 
into the continuous chain of the “ mutations of 
Waagen,” and for such progressive changes 
Deperet has proposed the term “ ascending mu¬ 

A 7 o theoretical conflict between the mutations 
of Waagen and of De Vries. It will he shown 
presently that a very considerable number, if not 
all, of these slow origins are of a kind which arise 
from internal causes (intrinsic causes, Williams), 
that is, in heredity. It is evident that if there do 
exist hereditary predispositions to mutate in def¬ 
inite directions, such predispositions may mani¬ 
fest themselves very gradually, as in the “ muta¬ 
tions of Waagen,” or under certain circum¬ 
stances very suddenly, as in the lesser saltations 
or “mutations of De Vries.” Theoretically, at 
least, there thus ceases to be any inherent conflict 
between the hypotheses of “ continuity ” and 
“ discontinuity ”; the latter may represent an in¬ 
tensified or accelerated state of the former. 




Adaptive nature of certain new origins . Dar¬ 
win’s hypothesis of the selection of variations 
lacking direction is essentially a law of chance. 
Origins of many kinds and in many places 
should be observed; the principle of trial and 
error should be seen in operation; paleontology 
should be an especially favorable field for such 
observation. Yet, as noted above, the mutation 
law of Waagen and the identical or similar rec- 
tigradation law of Osborn is essentially a prin¬ 
ciple of definiteness and determinateness from the 

Definiteness is not necessarily adaptiveness. 
The novel feature of Osborn’s observations in 
1889 on the cusps of the teeth appears to consist 
in the demonstration of this element of adaptive¬ 
ness ; 1 the new element is not merely determi¬ 
nate, hut it is leading directly to utility, and will 
at a later stage be useful. Thus vertebrate pale¬ 
ontology enables us to establish the law that cer¬ 
tain origins are adaptive in direction from the 
beginning; namely, the law of rectigradation. 

Such origins of new characters are chiefly 
numerical ; something is added to the organ or 
to the organism which did not exist before in vis- 

1 “ Certain Principles of Progressively Adaptive Variation 
Observed in Fossil Series.” Biological Section of the British Asso¬ 
ciation for the Advancement of Science, British Association 
Reports, 1894, p. 643 (title); Nature, Vol. 50, No. 1296, August, 
30, 1894, p. 435. 




ible form, such as the beginning of a cusp or of 
a horn. The origin of horns has always been a 
famous problem, because horns are eminently in 
the nature of new characters. In the great quad¬ 
rupeds known as titanotheres rudiments of horns 
first arise independently at certain definite parts 
of the skull; they arise at first alike in both sexes, 
or asexually; then they become sexual, or chiefly 
characteristic of males; then they rapidly evolve 
in the males while being arrested in development 
in the females; finally they become in some of 
these animals dominant characters to which all 
others bend. 

The form, the proportion, the modeling, both 
of the cusps and of the horns, accord with the 
proportions of the teeth or of the skulls in which 
they appear; they are thus correlated in form 
with other organs. The cusps of the grinding 
teeth of mammals form a peculiarly advanta¬ 
geous field of observation because they do not 
depend either upon ontogeny or environment for 
their perfection; they are born complete and per¬ 
fect, use and environment destroy rather than 
perfect them. They thus contrast with the 
bones, muscles, and many other tissues of the 
body which depend upon ontogeny for their per¬ 

Failure of attempted explanation of adaptive 
origins by transmission of acquired characters. 
In seeking explanation of this definiteness or 
adaptiveness of direction in the origin of certain 


new parts, it was natural to first have recourse to 
the doctrine of the transmission of acquired char¬ 
acters, because it is a well-known principle that 
certain organs are definitely directed or guided 
along adaptive lines by use. By reference to my 
papers of 1889 and 1890, it will be seen that it 
was in seeking an explanation of direction , I was 
led to support the Lamarckian principle. I do 
not propose to discuss this enormous question 
here. Cope concentrated his whole energy on 
trying to demonstrate Lamarckianism from pa¬ 
leontology, but ended in a logical failure, or non 
sequitur, because the explanation will not apply 
to all cases. Here again I believe that experi¬ 
mental zoology rather than paleontology is the 
best field of research, and that the Lamarckian 
principle should not be finally abandoned until 
it is tested by a prolonged series of experiments 
extending over many years. It is well known 
that Darwin, for the very reason that he thought 
he saw in it a working explanation of a directing 
influence on heredity, finally adopted the La¬ 
marckian principle and proposed his hypothesis 
of pangenesis. This was also the ground of my 
first conclusion of 1889, yet owing in the first 
instance to a trenchant criticism by Poulton, I 
have for the time abandoned this Lamarckian 
interpretation, since quite apart from the difficul¬ 
ties in the field of heredity, paleontology appears 
to offer many objections to it. The objections 
are simply these: that a very large number of 



new, definite, orthogenetic characters which could 
not have been acquired in ontogeny arise at birth, 
among them the cusps of the teeth. Since the 
Lamarckian doctrine either fails or need not be 
invoked to explain these definite adaptive origins 
in the teeth, and apparently also in the horns, 
why invoke it for other adaptive phenomena? 
This does not preclude the constant operation of 
the law of organic selection 1 or the “ selection 
of coincident variations ” advocated by Morgan, 
Baldwin, and myself, which I still regard as a 
useful supplementary hypothesis to Natural Se¬ 
lection, explaining many of the alleged instances 
of the inheritance of acquired characters. 

Unknown causes of certain adaptive origins. 
In 1890 I pointed out that, since the Lamarckian 
principle gave us a working hypothesis of direc¬ 
tion in these adaptive origins, in abandoning the 
Lamarckian principle we would be left without 
any explanation, and in developing this idea I 
came to the conclusion in 1895 2 that we must 
appeal to the existence of some unknown factor 

1 Osborn H. F.: “A Mode of Evolution Requiring Neither 
Natural Selection nor the Inheritance of Acquired Characters 
(Organic Selection),” Trans. N. Y. Acad. Sci., March and April, 
1896, pp. 141-48. 

See also: “ Ontogenic and Phylogenic Variation,” Science, 
Vol. IV, 1896, November 27, pp. 786-90; “Organic Selection,” 
Science, N. S., Vol. VI, No. 146, October 15, 1897, pp. 583-87; 
“ The Limits of Organic Selection,” American Naturalist, Vol. 
XXI, November, 1897, pp. 944-51; “Modification and Variation, 
and the Limits of Organic Selection: A Joint Discussion with 
Professor Edward B. Poulton of Oxford University,” Proc. Amer. 
Assoc. Adv. Science, Vol. 46, 1897, p. 239. 

2 “ The Hereditary Mechanism and the Search for the Unknown 
Factors of Evolution,” Biol. Led. Marine Biol. Lab. 1894, Ginn & 
Co., Boston, 1895. 



or factors of evolution. Subsequent research 
has convinced me that in these phenomena of the 
internal origin first of certain determinate char¬ 
acters, and second of certain adaptive charac¬ 
ters, we are dealing with the unknown if not with 
the unknowable, although the latter despairing 
attitude should not be hastily adopted. The 
immediate causes are internal, that is, tliev lie in 
the domain of heredity rather than of ontogeny, 
environment, or selection; but lest I might he 
mistaken on this point, I have devoted several 
years of thought to the development of a circle 
of causes , so to speak, which I have finally formu¬ 
lated 1 in the law called the four inseparable fac¬ 
tors of evolution. According to this law I re¬ 
gard heredity not as something inseparable, al¬ 
though extraordinarily stable; on the contrary I 
have recently expressed the relations of heredity 
to the other factors as follows:— 

The life and evolution of organisms contin¬ 
uously center around the processes which we 
term heredity , ontogeny, environment , and se¬ 
lection; these have been inseparable and inter¬ 
acting from the beginning ; a change introduced 
or initiated through any one of these factors 
causes a change in all. First, that while insep¬ 
arable from the others , each process may in cer- 

1 The Four Inseparable Factors of Evolution. Theory of 
Their Distinct and Combined Action in the Transformation of 
the Titanotheres, an Extinct Family of Hoofed Animals in the 
Order Perissodactyla,” Science, N. S., Vol. XXVII, No. 682, 
January 24, 1908, pp. 148-50. 


tain conditions become an initiative or leading 
factor; second , that in complex organisms one 
factor may at the same time be initiative to an¬ 
other group of characters, the inseparable action 
bringing about a continuously harmonious result . 

This inseparableness of internal processes (he¬ 
redity and ontogeny) and external processes 
(selection and environment) is not surprising 
when we reflect that it must have existed from 
the very beginnings of the organic world. 

Thus hypothetically the origins of certain new 
characters in heredity may find expression not 
spontaneously, or irrespective of conditions, or 
from self-operating internal mechanical causes, 
but through some unknown and at present en¬ 
tirely inconceivable relation between heredity 
(the germ-cells), ontogeny or habit and use (the 
somatic cells), environment or external condi¬ 
tions, and selection. This does not preclude 
spontaneous origins. 

Prolonged analysis and synthesis of the evolu¬ 
tion processes of the various kinds which led to 
the enunciation of the above law only served to 
convince me that certain adaptive origins are im¬ 
mediately matters of heredity whatever their in¬ 
itiation may be in the circle of ontogenetic or 
environmental causes. We have to do with a 
potential of similar mutations or rectigradations 

Here we find ourselves expanding a principle 
which was clearly foreshadowed by Darwin, and 



which, had he pursued it to its logical sequence, 
would have brought him to orthogenesis, namely, 
that variations may not be without direction, but 
that law may lie among the hidden recesses of the 
nature of the organism; in other words, Darwin 
himself frequently professed ignorance of the laws 
of variation as well as the belief that such laws 
might be discovered. Paleontology has revealed 
certain laws of variation, and it is quite con¬ 
sistent with the principle that the ancestral nature 
of the organism limits and conditions variation 

that I have to record the following interpretation 
or hypothesis 1 announced in 1902, namely, that 
the adaptive origins of certain characters are 
predetermined hy hereditary kinship. This pre¬ 
determination may be due to a similarity of 
hereditary potential in evolution, that is, ani¬ 
mals of similar kinship transmit similar poten¬ 
tialities in the origin of new characters. There 
is an ordinal kinship, a family kinship, a generic 
kinship, etc. This first renders possible the oc¬ 
currence of certain new characters, and second, 
conditions or limits these new characters when 
they do occur. For example, in a certain inde¬ 
pendent series of extinct animals derived from 
common ancestors, we can predict where a new 
cusp or a new horn rudiment will show itself be- 

1 Osborn, H. F.: “ Homoplasy as a Law of Latent or Potential 
Homology,” American Naturalist, Vol. XXXVI, April, 1902, pp. 

The term Homoplasy was wrongly employed in this paper under 
a misapprehension as to the significance which its author, Pro¬ 
fessor E. Ray Lankester, intended to apply to it. 



fore the actual occurrence of either. It is only 
through some such restraining or limiting law of 
hereditary kinship and potential that we can 
explain the marvelous uniformity which exists, 
for example, in the fundamental structure of the 
grinding teeth of the mammalia. 

Hypothetical interpretation. This is not to be 
understood as an internal perfecting tendency. 
Such an interpretation may be abandoned at once 
so far as it applies to the independence of these 
hereditary origins from other causes. While a 
phenomenon of heredity, the definite origin of 
adaptive structures is, in a manner which is en¬ 
tirely incomprehensible to us, related to ontogeny 
and environment, to new habits and new condi¬ 
tions of life, there is a marvelous neocus be¬ 
tween the internal and the external. Thus, for 
example, if a monkey or lemur begins to imitate 
the habits of the hoofed animals by becoming 
herbivorous, it also begins to acquire the dental 
cusps of the herbivorous hoofed animals in ap¬ 
proximately the same order. This principle of 
the relation of the internal and the external lies 
at the basis of many of the phenomena of par¬ 
allelism. For example, some of the Eocene 
monkeys so closely parallel the Eocene hoofed 
mammals in dental structure that they were first 
placed in the same taxonomic order. Some un¬ 
known relation between external and internal 
causes appears to evoke the potential of similar 
development. Thus there appear to be accelera- 



tions and retardations of characters in heredity 
which remind us of the well understood laws of 
acceleration and retardation in individual de¬ 

Degrees of kinship also affect to a certain ex¬ 
tent, but not absolutely, the time of appearance 
or the time of origin of new characters as well as 
the rate of their development. Thus four lines 
of Eocene quadrupeds (Titanotheres) branched 
off independently from one stock; in all the 
branches we observe similar new cusps arising on 
the premolar grinding teeth, and similar new 
horn rudiments rising on the forehead above the 
eyes, both independently evolved. Neither the 
new cusps nor the new hornlets appear at just 
the same moment of geological time; some phyla 
hasten forward these rectigradations, other phyla 
retard them. 

The independence of single characters and 
multiplicity of origins. The independence of 
single characters reminds us of the independence 
of the “ unit characters ” as known to the stu¬ 
dents of Mendelism and of De Vries’ mutation, 
yet the single characters we have in mind are not 
unit characters in the Mendelian sense because 
they do not mendelize; they appear in every indi¬ 
vidual. The independence of single characters 
in the “ Waagen mutations ” or the “ Osborn 
rectigradations ” is shown by the fact that a con¬ 
siderable number of characters evolve in a per¬ 
fectly regular and lawful succession. Each char- 



acter is a law unto itself, yet all subserve the gen¬ 
eral good. For example, a new horn rudiment 
arising on a brachycephalic skull will be broad 
or rounded; if it arises on a dolichocephalic skull 
it will be elongate or oval. Thus in a large quad¬ 
ruped like a horse, a tapir, a titanothere, or a 
rhinoceros each horn, each tooth, each bone of 
the skull and skeleton, and by inference all 
the hard parts as well as all the soft parts of 
these animals in each phylum, have two sets of 

I. In the origin of new characters each phylum 
will evolve, like other phyla, hypothetically 
through inherited predispositions. Thus from 
forty to forty-eight new characters will similarly 
arise in a number of phyla in the grinding teeth 

II. In changes of proportion and in rate of 
evolution each phylum will evolve unlike other 
phyla, through freedom from hereditary predis¬ 
position in matters of form, proportion, and rate 
of evolution. 

These are the conclusions which I have reached 
after twenty-two years of very precise work on 
the evolution of the mammals. Besides exactly 
observing primates, horses, rhinoceroses, during 
the past seven years I have devoted myself to 
still more precise monographic work on the group 
of titanotheres, bringing together great quanti¬ 
ties of material, and with the assistance of Mr. 
W. K. Gregory making thousands of exact oh- 



servations and measurements. Thus the evo¬ 
lution of the group has been traced from a small, 
hornless animal, of the size of a sheep, to a 
gigantic horned quadruped little inferior to an 
elephant. I have realized that the origin of all 
changes which are discovered in the skeleton must 
be credited to one of the four factors which take 
part in evolution, namely:— 





Thus new characters which can not be credited 
immediately to selection, to ontogeny, to environ¬ 
ment, must by exclusion be attributed to heredity, 
these are the mutations or rectigradations. 


An interpretation of the evolution of a family. 
In picturing the evolution of this great famliy 
of quadrupeds, the titanotheres, through a long 
period of time and with an unique sequence of 
material, may we not interpret the facts by imag¬ 
ining a continuous interoperation of the four 
chief factors, and analyze what we see somewhat 
as follows? 

First, these animals are all of the titanothere 
kinship and of the larger perissodactyl kinship. 
The ordinal kinship and the family consanguinity 


A. <5-0 


Rectigradations in tiie Teeth of Eocene Ungulates. 

A. A primitive Equid, Orohipnus sp. 

B. A primitive Titanothere, Palceosyopspaludosus. 

From specimens in the American Museum of Natural History. Internal view 
of lower teeth. 

The circles mark the cusps which appear independently in the different phyla ; 
they are at first barely visible but increase in size in successive geological levels. 

Top View of Three Skulls of Eocene Titanotiieres Illustrating 
Brachycephaly, Mesaticephaly, and Doliciiocepiialy Respect¬ 

(From specimens in the American Museum of Natural History.) 

A. Pakeosyops major , brachycephalic. 

B. Manteoceras rnanteocei as, mesaticephalic. 

C. Dolichorhinus cornutas, dolichocephalic. 



(different from that of the tapirs, rhinoceroses, 
or horses) apparently tincture and condition 
many things which happen in the evolution of 
this group. There are forty-four grinding teeth 
altogether; twelve of these teeth (the molars) 
early attain their final form, but are destined 
through family kinship to lose certain characters 
and to change their proportions through generic 
kinship; twelve others (the premolars) have not 
attained their final form, but gradually do so 
through the origin of from forty to forty-eight 
new characters, each of which appears to arise 
through an unknown law of hereditary predispo¬ 
sition, which operates alike, through ordinal kin¬ 
ship, not only in the titanotheres but in all other 
odd-toed or perissodactyl mammals to which the 
titanotheres are related. Changes of proportion 
in the skull, whether toward breadth (brachy- 
cephaly), or toward length (dolichocephaly), af¬ 
fect the form of the grinders as a whole and thus 
the birth-form of each of these new cusps. The 
immediate cause of changes of proportion is not 
interpreted as due to hereditary predisposition, 
because in teeth, in skull, in foot and limb, and 
even in horns each generic branch or phylum from 
the original stem forms of titanotheres acquires 
its own proportions. Thus changes of proportion 
are interpreted rather as immediately affected by 
ontogeny, by the mechanics of use and disuse, by 
an environment which favors some rather than 
other proportions, but especially by the selection 


of variations in proportion which coincide with 
the needs of the phylum . 1 

No abrupt variations (mutations) have been 
observed in the evolution of the titanotheres, but 
this in no way renders it inconceivable that skel¬ 
etal mutations in the De Vries sense have pro¬ 
duced new races in certain phyla. The addition 
or loss of a vertebra in the sacral region, which 
appears to distinguish certain titanothere phyla, 
may be a case of such sudden inheritable muta¬ 

Independently in four or five Eocene branches 
of the titanothere stock the horn rudiments very 
gradually arise, apparently through hereditary 
predisposition or family kinship, as rectigrada- 
tions, at the junction of the nasal and frontal 
bones. As in the case of the cusps, the shape of 
these horn rudiments is from the first conditioned 
by the respective breadth (brachycephaly) or 
length (dolichocephaly) of the skull. 

The branches or sub-phyla become more and 
more sharply distinguished from each other 
by increasing brachycephaly or dolichocephaly, 
brachypody or dolichopody, apparently through 
congenital variations of proportion accumulated 
by selection and guided by ontogeny through 
“ organic selection.'’ The animals belonging to 

1 It is important to note, on the authority of Professor Castle, 
that proportions of the skeleton and probably of the teeth are not 
inherited as distinct “ unit characters.” Inheritance of bone size 
and shape seems to be as a rule regularly blended by interbreed¬ 
ing and without subsequent Mendelian splitting. 


these branches appear to have chosen their own 
local environments, whether in localities favor¬ 
able to grazing or to browsing, and in turn con¬ 
genital changes of proportion would be favored 
by selection if in the right direction. The trans¬ 
formation into brachycephaly and dolichocephaly 
is brought about through independent changes of 
proportion in every bone of the skull, as ascer¬ 
tained by exact comparative measurements. A 
trend once established in either direction seems to 
constitute a sort of “ hereditary momentum ” or 
predisposition, which leads to great extremes of 
brachycephaly, on the one hand, or dolichoceph¬ 
aly on the other, as shown in the accompanying 
cut. The rudimentary horns, at first barely no¬ 
ticeable as the faintest convexities of the skull 
invariably appearing at the junction of the 
frontals and nasals, and produced by a thicken¬ 
ing of the cellular spaces, are first observed of 
equal size in the males and females; later they 
become more prominent in the males than in the 
females; finally they assume vast proportions in 
the males and present an arrested development 
in the females. At the summit of the Eocene 
the extreme dolichocephalic and brachycephalic 
phyla die out, and in the Oligocene a new series 
of phyla arise. Among these the long-horned 
forms appear through selection to develop the 
horns at the expense of other characters, the 
males with the longest horns probably securing 
the most females and becoming the chief breed- 



ers. It is especially noteworthy that in these 
long-horned phyla the main incidence of selection 
seems to he diverted to the horns from the teeth 
which appear to be dwarfed or arrested in evolu¬ 
tion. In the short-horned phyla, on the other 
hand, including one series at least, protected by 
more slender limbs and more rapid movements, 
the teeth are constantly sharpened and improved; 
this may be interpreted as caused by the selection 
of changes of proportion in the teeth. 

The teeth, however, of all these phyla of 
titanotheres are of a mechanical type which does 
not admit of further evolution; they have reached 
a stage which is a cul-de-sac / beyond which no 
progress is possible. The change of environment 
and of flora, therefore, finds these animals inca¬ 
pable of further mechanical betterment either 
through heredity or through the selection of vari¬ 
ations of proportion. All the titanotheres be¬ 
come suddenly extinct, and it is noteworthy that 
all other herbivorous quadrupeds having this cul- 
de-sac type of grinding tooth also became extinct 
in North America and in Europe either during 
the Oligocene or Miocene periods. 

This is an outline of the only theoretical inter¬ 
pretation which can he offered at present. In it 
heredity, ontogeny, environment, and selection 
are supposed to he in continuous interaction or 

1 Osborn, H. F.: “Rise of the Mammalia in North America.” 
Vice-Presidential Address before the American Association for 
the Advancement of Science. Section of Zoology. Madison, 
Wis., August 7, 1893. 


interplay. One feature has been omitted: that 
is, that all the branches of all the phyla, with one 
exception, show a continuous and progressive in¬ 
crease in size. This increase in size is, however, 
itself interpreted not only as a response to favor¬ 
able environment, but also to the selection of he¬ 
reditary variations in size due to the fact that 
the larger quadrupeds are better able to stand 
off the attacks of their carnivorous enemies. 


This interpretation, finally, is seen to include 
the cooperation of factors recognized by Buff on, 
by Lamarck, and by Darwin, except as to the 
transmission of acquired characters, which is left 
in doubt. There is, however, a new principle in 
the “ mutation of Waagen ” or “ rectigradations 
of Osborn,” unknown to Darwin and due to 
causes entirely unknown to us at the present time, 
and perhaps, as already intimated, unknowable. 
In this connection it is interesting to recall the 
comment of Aristotle 1 on the survival-of-the- 
fittest theory (the bracketed insertions [ ] and 
italics are our own) :— 

“ What, then, hinders but that the parts in Nature 
may also thus arise [namely, according to law]. For 
instance, that the teeth should arise from necessity, the 
front teeth sharp and adapted to divide food, the 
grinders broad and adapted to breaking the food into 

1 Osborn, H. F.: From the Greeks to Darwin , 8vo, Macmillan 
& Co., 1894, p. 55. 



“ [Another explanation may be offered.] Yet, it may 
be said, that they were not made for this purpose [i.e. 
for this adaptation], but that this [adaptive] purposive 
arrangement came about by chance; and the same 
reasoning is applied to other parts of the body in which 
existence for some purpose is apparent. And, it is 
argued, that where all things happened as if they were 
made for some purpose, being aptly [ adaptively ] united 
by chance , these were preserved , but such as were not 
aptly [ adaptively ] made , these were lost and still perish , 
according to what Empedocles says concerning the bull 
species with human heads. This, therefore, and sim¬ 
ilar reasoning, may lead some to doubt on this subject. 

“ It is, however, impossible that these [adaptive] 
parts should subsist [arise] in this manner ; for these 
parts, and everything which is produced in Nature, are 
either always, or, for the most part, thus [h e., adapt¬ 
ively] produced; and this is not the case with anything 
which is produced by fortune or chance, even as it does 
not appear to be fortune or chance that it frequently 
rains in wunter. ... If these things appear to be 
either by chance, or to be for some purpose, and we 
have shown that they can not be by chance, then it 
follows that they must be for some purpose. There is, 
therefore, a purpose in things which are produced by, 
and exist from, Nature.” 

Paleontology at present seems to support the 
philosophical contention of Aristotle, that when 
we come to the minute slowly progressing in¬ 
ternal changes, the fittest originates in law. 





The contributions of Darwin to psychology 
have not been adequately recognized. Not only 
in his famous seventh chapter on “ Instinct ” in 
the Origin of Species; in the second and third in 
the Descent of Man, comparing the psychic pow¬ 
ers of men and animals; in his Expressions of 
Emotions; and in Domestication , but sometimes 
in other works, he not only showed a depth of in¬ 
sight into, but laid anew the foundations of, 
genetic as well as comparative psychology. These 
should, and I believe will, eventually make him 
regarded as hardly less the founder of a new 
departure in this field than in that of classifica¬ 
tion, form, and structure. For him the soul of 
man is no whit less the offspring of that of ani¬ 
mals than is his body. Our psychic powers are 
new dispensations of theirs. The ascending 
series of gradations is no more broken for the 
psyche than for the soma. The gaps are no 
wider or more numerous from the lowest to the 
highest in the one than in the other. The affini¬ 
ties and analogies are as close, and the soul in- 




herits as much from our venerable, brute for¬ 
bears as does the body. The rudiments are as 
numerous and, to those who can rightly interpret 
them, as significant. From the higher anthro¬ 
poids, we need to go down the evolutionary stage 
but a little way to span an interval quite as great 
as that separating even the existing great apes 
from the lowest savages. 

But Darwin’s method is always and every¬ 
where objective and observational, never sub¬ 
jective or introspective. Few who have ever 
written about the mind of man know or say so 
little about consciousness, which has spun its 
Merlin spell of enchantment about our craft and 
all its works and ways. His language is the con¬ 
crete facts of life and mind, and not the categories 
and intuitions that an ingrowing intellect loves 
to manipulate. The brute soul explains that of 
man, rather more than man explains the brute; 
the unconscious explains the conscious and not 
conversely. He posits a natural history rather 
than a philosophy of mind. As Steinthal said 
language could be studied only historically— 

Sie ist was sie geworden ”—so for Darwin the 
true, ultimate knowledge of our psyche is the de¬ 
scription of all developmental stages from the 
amoeba up; and those move most surely among 
the altitudes who have most carefully explored 
the depths in which the highest human powers 
originate. Emotions are best studied in their 
outward expressions in gesture, will is investi- 


gated by the study of behavior, intelligence by 
massed instances of sagacity, and not by analysis 
under old rubrics. While he would have wel¬ 
comed all the illuminating experiments and tests 
under controlled conditions, which have lately 
given us such a wealth of insight, he would prob¬ 
ably have preferred careful observations of ani¬ 
mals afield in their accustomed habitat. Let us 
psychologists find in this celebration motivation 
to re-read his masterful contributions to our sci¬ 
ence, for nothing in our perhaps all too copious 
literature so grows upon the mind by frequent 
reperusal; and thus only shall we profit to the 
full, as we have been tardier than the biologists 
in doing, by the method, direction, and inspira¬ 
tion he so abundantly offers us. 



Probably most psychologists in our day accept 
evolution in a general way and have only praise 
for Darwin; yet I can think of but very few 
whose interest in the studies of the soul is pre¬ 
dominately evolutionary or very much influenced 
even by Herbert Spencer. Students of instinct 
have profited most here, although many of their 
studies are made under artificial and highly- 
specialized aspects, with too little reference to 
life history and habits of the species in the state 
of nature. The human mind is, for the most 
part, now studied introspectively, not only by the 



literary psychologists but in the laboratory, 
which is more and more regarded as a method 
and microscope of subjective analysis. Even 
Wundt approached psychology from the stand¬ 
point of physics and physiology, and his great 
text-hook would have been but very little differ¬ 
ent had Darwin never lived. The doctrine of 
apperception and even of feeling, with its recent, 
labored, introspective discussions of peripheral 
versus central origin and tri-dimensional theories, 
very rarely considers any developmental aspects; 
and this is one reason why, as has lately been so 
ably pointed out, neither Wundt nor the other 
standard text-books offer anv aid to the student 
of abnormal psychology or of instinct. 

Meanwhile, our science has had a prodigious 
and sudden horizontal expansion far beyond the 
old themes and limits. We have a psychology 
of religion, with a more special literature on such 
subjects as conversion, atonement, faith, posses¬ 
sion, holy spirit, inspiration, immortality, proph¬ 
ecy, prayer, Sabbath, and even the process of 
dying, sin, and demonology. Then there is the 
new psychology of crime, under its special ru¬ 
brics, murder, theft, arson, rape, suicide, fraud, 
and swindling, with traits of the chief classes of 
criminals. Hypnotism and suggestion, not to 
mention ghosts and telepathy, have opened an¬ 
other field. Then we have the psychology of 
sex in its normal and morbid manifestations, 
psychic differences, eugenics, and moral prophy- 


laxis. There is the psychology of language, ges¬ 
ture, music, imitation, social instincts, truthful¬ 
ness, infancy, childhood, adolescence, pedagogy, 
property, play, genius, and prodigies, sleight-of- 
hand, advertising, war, second breath, leader¬ 
ship, provincialism, business and panic, psy¬ 
chic epidemics, and many more, not to speak 
of the long list of admirable studies of excep¬ 
tional individuals from Helen Keller to Miss 
Beauchamp, Flournoy’s Mile. Smith, Beers, 
Monod, and Mrs. Piper. Instead of restricting 
himself to the classic, old themes of memory, as¬ 
sociation, logic, freedom of the will, conscience, 
in more or less academic seclusion and aloofness, 
the modern psychologist is often consulted by 
parents, pedagogues, lawyers, legislative com¬ 
mittees; lectures before popular audiences; or 
writes books and articles in a catchy, impression¬ 
istic style, with great attention to phrase-making. 

Thus, present themes are so absorbing, so many 
and so new, that if we are not beginning to 
lose sight of each other, we have lacked time and 
incentive to keep posted and interested all over 
the field, until now the task has grown beyond the 
ability of any one less gifted than Darwin to mas¬ 
ter details, see perspective, and mosaic items into 
true, evolutionary order which can alone bring 
unity into this teeming but now chaotic domain. 
The material for perhaps the most majestic struc¬ 
ture yet reared by science is already quarried. 
The need of and call for a master builder in this 


field must, ere long, produce the man. Some of 
us are already convinced that the human soul in 
all its power is just as much a product of evolu¬ 
tion as the body; but our faith needs to add the 
knowledge that can only come when all the au¬ 
thentic data are properly grouped. That the 
impending synthesis must be genetic, not in the 
prolix and platitudinous sense of Spencer, but 
with concrete facts as warp and woof, is inevita¬ 
ble if the psychology of the future is to correlate 
the facts of instinct, of daily human life with all 
its hot and intense impulses and all its morbid 
manifestations, and so become the Bible of the 
soul of man, in a sense our current, fragmentary 
systems do not dream of—this seems to me to be 


The signs and foregleams of such a recon¬ 
struction and transvolution are already many. 
In abnormal psychology, devolution is a rubric 
of increasing dominance. The Jacksonian the¬ 
ory of epilepsy brings in the genetic perspective 
in its conceptions of higher and lower levels. 
The studies of sex perversions are replete with 
references to the past history of the race, and 
some of them can be explained only as reversions, 
as in the case of the impulsions to nudity and ex¬ 
hibitionism. Many of the psychic facts in hu¬ 
man courtship point directly to that of animals. 
Some of the laws of the long-circuiting of the 


genesic instinct into secondary sex qualities are 
the same for brute and man. The more we know 
of this instinct the more orderly and unbroken 
becomes the progression upward and the closer 
the parallel. Even the differences are more and 
more explicable. The same is true of the care 
of the young, where the basal phenomena are 
common to all the higher mammals, and some of 
them to all viviparous creatures. Again, the cor¬ 
respondences between adolescence and senescence 
are, in some cardinal points, strangely comple¬ 
mentary. Here, too, should be mentioned the 
striking morphological, pathological, and psychic 
indications from the study of childhood that 
puberty once came much earlier in our forbears, 
the autogenetic inferences in this direction, how¬ 
ever, being as yet too slightly supported by phy- 
letic facts, on account of the necessary imperfec¬ 
tions of the record. Perhaps best of all as an il¬ 
lustration is the new psycholog}?- of crime and 
criminals, who are so shot through, body and 
soul, with atavisms that only the early history of 
the race can explain them. 

Again, if we eliminate from the later studies 
of mental diseases, all the evolutionary elements 
and suggestions, they would be robbed of no lit¬ 
tle value. I refer especially to psychasthenic and 
dissolutive states, to certain of the phobias, fuges, 
imperative ideas, to various eruptive or fulminat¬ 
ing phenomena and psycholeptic crises, and to the 
formation of the more or less subconscious con- 



stellations of psychic elements, which may act 
like foreign bodies in the soul, and some of which 
are peculiarly suggestive of atavistic or outgrown 
states. Here, too, belong many phenomena of 
hypnoidization with more or less psychic decapi¬ 
tation—Verdichtung—(which probably repre¬ 
sents a type of psychoses that are peculiarly 
characteristic of prehistoric man, who ejected 
his subjective states much as Freud thinks that 
dreamers are doing, to say nothing of the latest 
studies of phonisms, photisms, and coenesthesias. 
It is studies in this field, it may also be men¬ 
tioned, that have led acute minds, like Bleuler, 
to violent polemics against consciousness as the 
muse of modern psychology, some of them insist¬ 
ing that hut little of the experience that has made 
the mind in its human form has been connected 
with either consciousness, apperception, or even 
attention. The view is unquestionably gaining 
ground that consciousness is an epiphenomenon 
of mind, and that its function is essentially no 
less remedial or cathartic than the church has 
held confession to he, though in a somewhat dif¬ 
ferent way. There is no better test of a psycho¬ 
logical system than its applicability to psychi¬ 
atry; and it is here that Wundt so signally fails, 
for his fundamental assumption is that conscious¬ 
ness is the condition of all psychic experience, 
and he defines even feeling as a “ subjective reac¬ 
tion of consciousness.” In fact, on the contrary, 
there are incessant and manifold affective and 


other processes going on in us that lack conscious¬ 
ness, although they often resemble it in them¬ 
selves and in their influence upon us, and which 
can not be ignored because they often dominate 
psychopathic symptoms and also our normal 
lives. These are processes which become con¬ 
scious only when associated with the ego-com¬ 
plex. Many sudden choices, movements, feelings 
of anger and fear, and many other experiences 
sometimes lack all intellectual motivation as 
much as do melodic haunts. It is such states and 
activities, possibly mediated by sub-cortical areas, 
that irresistibly suggest past evolutionary stages 
of mentation, and it is also this group of under¬ 
lying processes that may put on and off suc¬ 
cessive, conscious personalities as garments. It 
is these deep yet dominant complexes that love, 
hate, shape many currents of conduct, before con¬ 
sciousness is aware of it, and which are constantly 
reinforcing and approving or censuring what con¬ 
sciousness does. They suffer or rejoice sometimes 
with, sometimes without, consciousness, which is 
only their very imperfect instrument. Per¬ 
haps nothing is ever fully conscious, while much 
that takes place in us may be wholly unconscious. 
To say with Raimann that “ there is no uncon¬ 
scious knowledge or with Hellpach that “ psy¬ 
chology deals only with consciousness,” and that 
“ the unconscious can not be an object of knowl¬ 
edge,” is a form of psycho-physic parallelism that 
amounts to obscurantism; while to urge, as we 


must, that even attention may be unconscious 
would shock even an alienist so speculative as 
Ziehen, who persistently identifies the psychic 
with the conscious. 


Hardly less than animal instinct, child psy¬ 
chology, as Darwin in his famous observations 
on infancy, although not the first was perhaps the 
third to see, can only be explained on an evolu¬ 
tionary basis. The child, uncivilized and to some 
extent even savage, is precociously thrust into 
an environment saturated with adult influences 
because of language and accumulated grown-up 
customs, traditions, and ideas; and for this rea¬ 
son as well as because of its intense, imitative pro¬ 
pensities tends to be very early stripped of many 
of its psychic rudiments and recapitulatory 
traces. Yet the more we know the child, the 
more clearly do we see the germs of many ata¬ 
vistic tendencies nipped in the hud, though many 
of them have so long been. There can no longer 
he any doubt that the human infant not only 
tends to but occasionally does develop real words 
that are its own original creation, products of the 
rudiment of the same instinct in which language 
took its first rise. This vestige is thus not com¬ 
plete^ eliminated by the early, mimetic adoption 
of the speech of the environment. I have col¬ 
lected from the literature over two score of these 


words which, I believe, can not possibly be ex¬ 
plained as imitations, and which have been used 
consistently by the child for some time and occa¬ 
sionally for a number of years. So in infantile 
drawing we have undoubted, though dwindling, 
traces of what Verworn calls the physioplastic 
stage of paleolithic man, before the idioplastic 
stage of the neolith, who ceased to draw directly 
from the object itself but rather copied his own 
mental image of it. Here, again, a well-recog¬ 
nized phyletic stage has dwindled to little more 
than a filmy vestige in the modern infant, but is 
as recognizable as the rudimentary gill-slits in 
the embryo. The swimming, paddling move¬ 
ments, too, by new-born infants if supported in 
tepid water; the wonderful power to cling and 
support the weight for a minute or two during 
the first few weeks after birth, a power soon lost 
but reminscent of arboreal life; the phobias of 
infants of a few w T eeks or months seen often in 
nervous shudders at the first impressions of fur, 
big teeth and eyes; the joy experienced hy toss¬ 
ing and other levitation movements, creeping, 
and the processes of assuming the erect position; 
the very intricate and interesting stages of the 
progressive acquirement of the complex sense of 
self; the loud cry of the human infant from birth 
on as contrasted with the silence of the new-born 
of other animals, so eloquent of the early power 
of the parent to protect; and for older children 
fetishisms galore, gangs corresponding to the 


primitive tribes, propensity for hunting, killing, 
striking with clubs, pounding, stealing, etc., the 
sense of the power of the point, edge, string, and 
many forms of plays and toys, the nascent sense 
of death, and other items far too numerous to 
even catalogue here—all show that the child is 
vastly more ancient than the man, and that adult¬ 
hood is comparatively a novel structure built 
upon very antique foundations. The child is 
not so much the father of the man as his very 
venerable and, in his early stages, half-anthropoid 
ancestor. There can no longer be any question 
that its rudimentary psychic organs are no whit 
less numerous than the half-score of anatomical 
rudiments that Wiedersheim enumerates. Per¬ 
haps, in general, the traces of the psychic reca¬ 
pitulation of the history of the race are most 
traceable and most unbroken, faint as some of 
the traces are. Psycho-genesis, like embryology, 
shows many rudiments preserved and developed 
by being diverted to other than their original 
uses, although of very few psychic traits or func¬ 
tions have there been adequate material methods 
of record and preservation as structural details 
are preserved; nevertheless, they follow the same 
lapidary law and speak a language which, when 
it is set down and interpreted, is no less clear and 

In general, nearly every act, sensation, feel¬ 
ing, will, and thought of the young child tends 
to be paleopsychic just in proportion as the child 


is let alone or isolated from the influence of 
grown-ups, whose presence always tends to the 
elimination of these archaic elements, and in all 
cases makes havoc with them, over-repressing 
some that should have their brief fling, if only 
on the principle of the Aristotelian catharsis, to 
give early immunity from the hypertrophy of 
bestial traits by awakening the next higher pow¬ 
ers that repress them in their nascent period; but 
which, in some environments, are left to grow into 
faults and then into juvenile crimes, which they 
are prone to do just in proportion as the order of 
their nascency is perverted. Thus the problem 
of a true mentally, esthetically and morally or¬ 
thopedic education still gropes in the trial and 
error stage, although not without some progress 
toward a scientific basis for pedagogy which, if 
it ever comes, can rest on no other foundation 
than a well-established embryology of the soul, 
all the way from eugenics and the psychic states 
and regimen of pregnancy on to the fully ma¬ 
tured nubility of the offspring. Thus, from one 
point of view, infancy, childhood, and youth are 
three bunches of keys to unlock the past history 
of the race. Many of the keys, especially those 
which belong to the oldest bunch, are lost and 
others are in all stages of rust and decay. Many 
of the phyletic locks which they fit are also lost 
or broken; both locks and keys are often dis¬ 
torted and, to change the figure, the sequences 
which the race followed are often inverted in the 


autogenetic processional of growth; but, if the 
goal is still dim and far, it is unmistakable, and 
as we slowly and surely approach it, the genetic 
psychologist feels it beckoning, calling, and in¬ 
spiring, almost like a new muse. This has intro¬ 
duced a temporal perspective or new dimension 
into a field where most preceding and even pres¬ 
ent studies have all been in the flat surface of the 
present state of adult consciousness. This is sup¬ 
ported by, though still but very imperfectly cor¬ 
related with, the studies of animal instinct on the 
one hand, and with those of the myth, custom, and 
belief of primitive races on the other. It already 
suggests to the many laboratory studies of the 
affective life (based on the method of controlling 
the conditions of very slight variations of emo¬ 
tional tone exigously made and based only on a few 
adult experts), a more excellent way, which would 
tend to bring psychology back to the study of 
human life as it is lived out, where it is hottest, 
most intense and passional with love, anger, fear, 
hate, jealousy, grim and dour struggles with sin, 
wrought out with sweat, blood, and supreme 
effort, with perhaps the life and death of the indi¬ 
vidual or even the race at stake. Here, rather 
than in the isolation of the laboratory or the 
study, lies the heart of a psychology that touches 
life and that really avails and has worth and 
value, because it is in line with the eternal pow¬ 
ers and is, in a word, a true, natural history of 
the soul, and can make “ philosophy ” again, as 


the motto of one of our best-known culture fra¬ 
ternities has it, “ the guide of life.” 


Finally, education, now perhaps the most uni¬ 
versal and uniform of all the social institutions, 
is now looking to psychology for guidance as 
never before, and we are at present able to meet 
this call in only a halting and partial way. Re¬ 
ligion seems of late to be becoming strangely 
docile to all the too little we have to teach it. 
Psychiatry, to which we should have at least 
given a science of normal psychic life, is now in 
danger of finding our texts of little avail in solv¬ 
ing its problems, is building new foundations of 
its own, and growing weary of our sophistic sub¬ 
tleties concerning parallelism and interaction and 
the nature of feeling, conscience, etc. Few, even 
of our recent experimental results, are available 
for determining or influencing normality or ab¬ 
normality; our discussions of freedom, necessity, 
or responsibility are too academic for use in crim¬ 
inology. The great newly discovered continent 
of the unconscious is still regarded by many mem¬ 
bers of our guild as mystical, perhaps superlim- 
inal, and its phenomena are used to cast augu¬ 
ries as to whether the soul is independent of or 
survives the body. The unconscious is really 
like the submerged eight-ninths of an iceberg, 
which is impelled by deeper currents in a denser 
medium, and which the glittering summits that 


emerge above the tide and are impelled by only 
atmospheric pressure have little control over. 
And once more, just as psychiatry is now chang¬ 
ing its emphasis from a predominantly somatic 
and neurological basis, which has been so fruitful 
under the old slogan of Virchow, “ LTbi est mor¬ 
bus,” to a more psychic, pathological viewpoint, 
so perhaps even the doctrine of heredity is com¬ 
ing our way by changing the terms applied to its 
elements from the mystic, pathological ids and 
determinations of Weismann to Semon’s no less 
mystic but psychological postulates of mnemes 
and engrams. Here, too, we are hardly ready to 
meet the new demands or utilize the new princi¬ 
ples, because our department is still, despite its 
great, recent progress, only half scientific and is 
not unlike Milton’s new-born tawny lion pawing 
to get away from the metaphysical and theolog¬ 
ical soil from which it sprang. We have too 
long yielded to the seductions of the heterai of 
the ancient, speculative problems that have ob¬ 
sessed us and not yet 
in our midst who still urge that psychology 
should be developed in the closest rapport with, 
if not under the influence of, a speculative phi¬ 

Finally, as Darwin freed biology from the in¬ 
veterate dominance of the ideas of fixed and 
divinely created species, conceptions directly in¬ 
herited from Plato’s ideas and Aristotle’s cate¬ 
gories, so everything in the present psychological 

definitely broken with those 


situation cries out for a new Darwin of the mind, 
who shall break the persistent spell of theoretical 
problems incapable of scientific solution, the ideal 
of a logical and methodical exactness greater 
than our subject in its present stage permits of, 
which Aristotle well dubbed pedantry, and re¬ 
mand the haunting problem of the ultimate 
nature of consciousness and the final goal of the 
psyche to the same limbo, by suspending convic¬ 
tions, as those of the constitution or cause of 
energy and the nature of reality and objectivity. 
Only by so doing can we again get up against the 
essential facts of life as it is lived out by the toil¬ 
ing, struggling men, women, and children, nor¬ 
mal and defective, of our day. If this rough 
diagnosis of the present situation is correct, only 
a pessimist can doubt that the need will, ere long, 
bring the man or the men to meet it in the only 
way it can he met, viz., by a comprehensive evo¬ 
lutionary synthesis in the psychological domain, 
which by every token seems at present to impend. 


Acquired characters, inheritance 
of, 34-43, 111, 112, 120-124, 
137, 204-206 

Adaptation, 41, 61-66, 213; ab¬ 
sence of, 61-66, 85; in muta¬ 
tions, 178; address on, 182- 
208; functional, 203 
Adapted environments, 183, 186 
Adapted faunas, 184 
Adjustment, self-, 42; to en¬ 
vironment, 116 

Agassiz, Alexander, theory of 
coral islands, 9 

Agassiz, Louis, unfavorable to 
Darwin, 27 
Albinism, 155, 169 
Argyll, Duke of, views of, 45 
Aristotle, quoted, 249 
Arrhenius, on origin of mat¬ 
ter, 46 

Artificial selection, 74; isolation 
in, 85 

Aster, evolution of genus, 58, 59 
Athenceum, review of Origin in, 

Bailey, on pouched gophers, 76 
Baldwin, J. M., organic selec¬ 
tion, 10, 48; effect of social 
environment, 30 

Barriers in species formation, 
81, 84 

Bates, H. W., hypothesis of 
mimicry, 47 

Bateson, W., variation in Kal- 
lima, 178; variation, 224-227 
Beagle, voyage of the, 8, 11, 12, 
192, 215 

Beccari, theory of evolution, 
24, 25 

Beetles, experiments upon, 124 
Bentham, 19 
Blind fishes, 189, 190, 200 
Blomeeield, L., word “ muta¬ 
tion,” 43 

Bonnet, C., forerunner of pan¬ 
genesis, 95 

Botany, debt to Darwin, 57 
Boveri, T., chromosome theory, 
103, 104 

Brachiopoda, 210, 211 
Brainerd, E., violets, 166 
Brown, R., 18 
Bud-sports, 130 

Buffon, 31, 215, 249; adapta¬ 
tion, 193, 204; evolution, 20; 
pangenesis, 95 

Burchell, W. J., 19; feelings 
in forest, 38; isolation, 30 

Carlyle, Mrs., on Owen, 31 
Carpenter, 19 

Castle, W. E., address by, 143- 

Catfishes, 200 

Cathedrals as awe inspirers, 36, 

Cave faunas, 184, 186-190 
Cell, in heredity and evolution, 

Chamberlin, T. C., address by, 

Chambers, R., evolution doc¬ 
trine, 20 

Characters, acquired (see: Ac¬ 
quired characters); new, 58- 
61, 223-233; origin of, 58-61; 
unit (see: Unit character) 
Characins, 192-196, 203 
Chemical nature of heredity, 

107, 163, 180 
Chromatin, 99-104 
Chromosomes, in fertilization, 

100, 103; radium on, 129, 138; 
role of, 107 

Climbing plants, debt to Asa 
Gray, 29 

Cognate species, 81 
Coleoptera, experiments with, 12 
Color, mendelian phenomena in, 

108, 152, 153 




Combs of cocks, 127, 171 
Continuity of germ-plasm, 35 
Continuous evolution, 48-50 
Cope, E. D., 9, 215, 229, 232 
Coral islands, Darwin’s theory 
of, 46 

Correns, C., rediscoverer of 
Mendelism, 145 
Coues, E., quoted, 78 
Coulter, J. M., address by, 57- 

Crime and evolution, 256 
Crocker, W., work on seeds, 62 
Cuvier, G., 215 
Cytoplasm in heredity, 101 

Dana, theory of coral islands, 9 
Darwin, C., 249; influence, 1; 
early life, 11; first attention 
to evolution, 7; first sketch of 
Origin, 13; prepares for pub¬ 
lication, 18; maturity of the 
Origin, 23; thrilled by anthem, 
38; on Leicester sheep, 76; on 
isolation, 87; on mutation, 
43-45, 163-165; work on galls, 
131, 132; on black peacock, 
169; adaptation, 193; rela¬ 
tion to paleontology, 212; 
psychology, 251-254, 260; let¬ 
ters: Huxlev, 10; Owen, 31; 
Wright, 32; Leidy, 209; 
Davidson, 210 

Darwin, Erasmus, Zoonomia , 
10; evolution, 20 
Darwin, Francis, on acquired 
characters, 39; presidential 
address, 39; letter about galls, 

Davenport, C. B., address by, 

Davidson, L., letter from Dar¬ 
win, 210 

Definite variations, 231 
De Vries, H., 242; intercellu¬ 
lar pangenesis, 93, 106, 144; 
premutation period, 132; re¬ 
discoverer of Mendelism, 145; 
mutation theory, 160, 229; 

cessation of selection, 174; 
adaptation, 193 

Differentiation and cytology, 

Directed variation, 236 

Discontinuous evolution, 48, 
140, 180, 227, 228 
Dollo, L., 229 

Ecology, 61 

Edinburgh Review, article by 
Owen, 31 

Education and evolution, 263, 


Effect of Origin, 54, 55 
Eigenmann, C. H., address, 

Eimer, T., orthogenesis, 193 
Elementary species, 166 
Elimination, 176, 177 
Emotions and evolution, 251 
Entelechy, 110 

Environment, adjustment to, 
117; factor in evolution, 244 
Enzymes in heredity 106-109 
Evening primrose, 130, 133, 165- 

Evolution first brought to Dar¬ 
win's attention, 8; of Gymno- 
sperms, 66-70; isolation in, 
72-91; cell in relation to, 92- 
113; role of environment in, 
114-142; and psychology, 251- 


Experimental morphology, 61 
Extra-floral nectaries, 63 
External factors, 115, 126, 197- 
207, 238, 239 

Factors of evolution, 238 
Factor hypothesis in heredity, 
108, 115, 150-158 
Farrer, Lord, letter of Dar¬ 
win to, 25 

Fawcett, H., defense of Dar¬ 
win, 8; letter to, from Dar¬ 
win, 21, 22; review of Origin, 
22, 34 

Ferments in heredity, 106 
Fertilization of egg, 108 
Fischer, E., experiments, 123 
Fiske, J., evolutionary teaching, 

Fitton, 19 

Fluctuation, limit to, 49, 173- 
176; in isolation, 85, 173 
Forbes, E., coral reefs, 46; 
views on arctic relics antici¬ 
pated by Darwin, 46 



Forbes, S. A., quoted, 167 
Forests, excite feeling, 36 
Forms of Flowers, dedicated 
to Asa Gray, 29 
Fortuitous variation, 226 
Freshwater fishes, 184 
Freud, 258 

Gage, S. H. and S. P., experi¬ 
ments, 121 

Gager, C. S., experiments with 
radium, 128, 138 
Galileo, effect of teaching, 55 
Galls, vegetable, 131 
Galton, F., effect of Origin, 
52; experiments on pangen¬ 
esis, 145 

Gartner, hybridization, 52, 53 
Gaudry, 215 
Geminate species, 81 
Gemmules, 95, 96 
“ Genesis of Species,” 32 
Genetic synthesis in psychology, 

Geographic convergence, 199, 
201; distribution, 73; varia¬ 
tion, 181, 196-198 
Geologic convergence, 200, 201 
Germ-plasm, continuity of, 35, 
40; influence of soma on, 120 
Goats, 164 

Gooseberry, cessation of varia¬ 
tion, 176 

Gosse, P., Omphalos , 15, 16 
Graduated tharacters, 127 
Gray, A., defense of Darwin, 
8; friendship with Darwin, 
26-29; Darwin’s opinion of, 
26; correspondence with Dar¬ 
win, 31, 44 
Gregory, W. K., 243 
Grove, Dr., interviews Tenny¬ 
son, 15 

Guinea-pig, 148, 149 
Gulick, J. T., 193 
Gurney, E., letter of Darwin 
to, 35 

Guthrie, C. C., experiments, 

Gymnosperms, phylogeny, 60; 
evolution without utility, 66 

Haeckel, E., on pangenesis, 40 
Hair, 151, 170 

Hall, G. Stanley, address by, 

Hall, James, the fossil record, 9 
Hallett, cessation of improve¬ 
ment in wheat, 48 
Hellpach, 259 
Henfrey, 19 

Henslow, J. S., friendship with 
Darwin, 11; opinion of Lyell’s 
Geology, 12; letter of Darwin 
to, 36 

Heredity (see also Inheritance), 
chemical nature of, 110; and 
memory, 112; determination 
of, 114; unit characters in, 
143-159; of mutations, 171; 
factor of evolution, 244 
Hering, on heredity, 39 
Hertwig, O., the nucleus in 
heredity, 99 

Hilgendorf, work of, 214 
Hofmeister, on plant relation¬ 
ships, 57 

Hooker, Sir Joseph, defense of 
Darwin, 8; advice asked by 
Darwin, 18; presents papers 
of Darwin and Wallace, 18, 
19; utility, 25; friendship with 
Darwin, 25, 26; letter of Dar¬ 
win to, about Mivart, 32; 
about pangenesis, 39; about 
limits to artificial selection, 
48; coral reefs, 46; letters 
from Darwin, 51, 94, 131 
Hooker, Sir William, letter 
from Burchell to, 38 
Hormones, 106, 109, 112 
Horns, 147, 164, 170, 240, 247 
Horner, L., letter to, 12 
Horse, 175 

Humboldt, Darwin on, 36 
Huxley, T. H., 215, 224; letter 
of Darwin to, 10; friendship 
with Darwin, 29; reviews 
Origin, 33; effect on study 
of biology, 53; on coming of 
age of the Origin, 54; op¬ 
posed to pangenesis, 93 
Hyatt, A., controversy with 
Darwin, 9; the fossil record, 
9; work of, 212, 213, 231 
Hybridity, and selection, 52; 
characters swamped by, 141, 


Idioplasm, 99 

Inheritance of acquired char¬ 
acters (see Acquired char¬ 

Intelligence and evolution, 253 
Intercrossing, checked by isola¬ 
tion, 75 

Internal secretions, 109, 112 
Intercellular pangenesis, 93 
Island faunas, 81 
Isolation in evolution, 72-91; 
role of, 75-80; and differenti¬ 
ation, 198 

James, W., leader of American 
psychology, 10; quoted, 224 
Jordan, David Starr, address 
by, 71-91 

Kallima, 177 

Karyokinetic division and he¬ 
redity, 103, 104 
Kingsley, C., quoted, 16 
Kolreuter, hybridism, 52 
Kowalevsky, 200, 215 

Lamarck, 215, 249; debt to 
Erasmus Darwin, 10; hy¬ 
pothesis, 34, 35; adaptation, 
193, 204 

Lane-Claypole, effect of fetus 
extract, 107 

Lankester, E. Ray, quoted, 29; 

“ homoplasy,” 240 
Leaf-butterfly, 177 
Leidy, J., 232; fossil record, 9; 
correspondence with Darwin, 

Lepidoptera, experiments upon, 

Linnean Society, meeting for 
Natural Selection papers, 18 
Lizards, 200 
Lotsy, J. P., 166 
Lyell, Charles, influence on 
Darwin, 12, 13, 29; presents 
the papers of Darwin and 
Wallace, 18, 19; prevents 

Dawson’s review, 21; letter 
of Darwin to, 45; coral reefs, 

MacDougal, D. T., chemical 
treatment of germ-cells, 110; 
address by, 114 
MacGregor, experiments, 128 
Malthus, influence on Darwin, 

Mammals, fossil, 213 
Mammary glands, stimulated by 
fetus extract, 107 
Marsh, O. C., 9, 215, 218, 232 
Matthews, 213 
Maturation, 103 
May beetles, 167 
Memory in heredity, 41, 112 
Mendel, G., 145 
Mendelism, 10, 144, 242; and 
pangenesis, 40; and heredity, 
100, 108, 152, 153 
Metabolic activities, irritable re¬ 
actions, 117 

Mill, J. S., opinion of Origin, 
22, 23 

Mitotic division in heredity, 

Mivart, St. George, opposition 
to Darwin, 31-33 
Moore, Aubrey, quoted, 17 
Morgan, Lloyd, organic selec¬ 
tion, 10, 48 

Muller, Fritz, defense of Dar¬ 
win, 8; letter of Darwin to, 39 
Murray, Andrew, crude theory 
of, 24 

Mutation, 202; bearing on pan¬ 
genesis, 40; Darwin’s views 
on, 43-46; origin, 111; ad¬ 
dress on, 160-181; and adap¬ 
tation, 194 
Myrmecophiles, 63 

Nageli, theory of evolution, 25; 
idioplasm, 144, 146; adapta¬ 
tion, 193 

Natural selection, 206; theory 
of, 10; discovery of, 11; pecu¬ 
liarities of, 14; opponents of, 
24; claimed by Owen, 31; in 
relation to mutation, 47; to 
hybridism, 52; to botany, 57- 
71; implies segregation, 85; 
not opposed to isolation 
theory, 89; and mutation, 
176; and adaptation, 192, 196 
Neo-Darwinism, 161-163 



Neo-Lamarckism and paleontol¬ 
ogy, 9, 237 
Neumayer, 213, 231 
Newton, effect of teachings, 55 
Nucleus, in heredity, 99, 105, 

Nussbaum, M., 98 

d’Orbigny, A., 12 
Oliver, 19 

Ontogeny, factor of evolution, 

Organic selection, 10, 48, 237 
Origin of life, not a subject 
for speculation, 46 
Origin of Species, reception of, 
2, 20-23; influence, 6; attacks 
on, 51 

Orthogenesis, 111, 197, 234-240 
Ortmann, quoted, 77 
Osborn, H. F., 11, 213, 231; 
fossil record, 9; theory of 
organic selection, 10, 48; or¬ 
thogenesis, 193; address by, 

Owen, R., 31; evolution doc¬ 
trine, 20; attack on Darwin¬ 
ism, 30; characters of fossils, 

Oxford, bishop of, attacks on 
Darwinism, 30 
Oxford University, 13, 33 

Paleontology, address, 209-250 
Pangenesis, 35, 39, 40, 92-97, 
106, 144, 236 
Parallel adaptations, 80 
Peacock, black-shouldered, 169 
Peas, 146 

Pedagogy and evolution, 146 
Penstemon, 135 

Permanence of ocean basins, 46 
Philosophie zoologique of La¬ 
marck, 11 

Pictet, nutrition of egg, 121 
Pigment, 147 

Polyphyletic origins, hypothesis 
of, 9 

Poulton, E. B., 236; address 
by, 8-56; Darwin’s views on 
variation, 217 
Poultry, 168-174 
Psychical nature of develop¬ 
ment, 109 

Psychiatry, 265 
Psychology and evolution, 251 
Pterydophytes, 70 

Rabbit, 149-159 
Rabl, C., 103 

Radium, effect on germ-plasm, 

Raimann, 259 

Recapitulation in psychology, 

Rectigradation, 231, 234, 239, 


Regeneration, Darwin on, 39, 97 
Religion, 265 

Remak, germinal continuity, 98 
Repetition of stimuli, 122 
Reversion, 151, 152 
Riddle, O., experiments, 121 
Rodents, variation of, 76 
Roentgen’s rays, experiments 
with, on germ-plasm, 127 
Romanes, G. J., Darwin’s con¬ 
scientiousness, 36 
Roux, W., significance of mi¬ 
tosis, 103 

Saint-Hilaire, 229 
Saltation, Darwin on, 165 
Scott, J., letter from Darwin 
to, 53 

Scott, W. B., fossil record, 9; 

quoted, 200, 213 
Secretions, internal, 112 
Sedgwick, A., friendship with 
Darwin, 11; criticises Dar¬ 
win, 21 

Seeds, origin of, 60; unadaptive 
characters in, 62 
Segregation, types of, 72; neces¬ 
sity of, 87 

Selection, 216-223, 244; artifi¬ 
cial selection, limits to, 48; 
role of, 59-61; cessation of, 
48, 174 

Selective migration, 185, 190 
Self-adjustment, 42 
Semon, R., on heredity, 39, 266 
Sex, 104 

Shade foliage and heredity, 42 
Sheep, isolation and develop¬ 
ment of races, 74-76, 86 
Shull, G. H., 166, 197 
Skull, 221 



Solutions, effect on germ-plasm, 

Spencer, H., 212, 253, 256; 

evolutionary teaching, 9 
Sporophytes, origin of, 60 
Standfuss, M., experiments, 123 
Starling, injection of fetus ex¬ 
tract, 107 

Strasburger, nucleus in hered¬ 
ity, 99 

Struggle for existence, 203 
Sublime, feelings of, 35, 38 
Swamping effects of intercross¬ 
ing, 179 

Teeth, 219, 232-234, 241,242, 248 
Temperature, check on migra¬ 
tion, 186 

Tennyson, A., the struggle for 
existence, 14-15 
Teratological characters, 173 
Testic extract, effect of, in¬ 
jected, 107 

Thyroid extract, effect of, 107 
Titanotheres, 242-249 
Tower, W. L., modification of 
germ-cells, 110, 125-127, 197 
Tschermak, E. v., rediscoverer 
of Mendelism, 145 
Tyndall, J., effect of Origin, 

Unit characters, 143-159; and 
mutation, 160, 161 
Use and disuse, inheritance of, 

Variability, somatic, in response 
to environment, 118 
Variations, small, 217, 220, 222; 
large, 217 

Vestiges of Creation, 31 
Verworn, M., 261 
Virchow, R., germinal continu¬ 
ity, 98 

Waagen, W., 249; orthogenesis, 
193; mutation, 211, 229-233, 
242; fossil series, 213 

Wagner, M., on isolation, 72, 88, 

Walcott, C. O., the fossil rec¬ 
ord, 9 

Walker, effect of testic extract, 

Wallace, A. R., in New World, 
7; natural selection, 18; ad¬ 
dress at Linnean Society’s 
Anniversary, 19; coral reefs, 
46; on isolation, 83 
Warner, C. D., feeling of awe, 

Weir, J. J., letter of Darwin 
to, 33 

Westwood, J. O., proposes read¬ 
er to combat Darwinism, 21 
Weismann, A., 35, 40; under¬ 
mined Lamarckism, 10; non- 
transmissibility of acquired 
characters, 10, 11; idioplasm, 
144; quoted, 161, 162, 183; 
adaptation, 193 
Weismannism, 118 
Wheat, limits to improvement, 

Wheeler, W. M., insect mu¬ 
tants, 166 

Whewell, Dr., excludes Origin 
from college library, 21 
Whitman, C. O., orthogenesis, 

Will, method of investigating 
the, 252 

Wilson, E. B., address by, 92- 
113; on chromosomes, 129 
Wallaston, on wingless oceanic 
beetles, 47 
Woodward, S., 229 
Wright, C., defense of Darwin, 
8; review of Mivart, 32-34 
Wundt, 254 

X-rays, experiments with, on 
germ-plasm, 127 

Ziehen, 259 

Zoonomia, influence on La¬ 
marck, 10 


By Prof. Vernon L. Kellogg, of Leland Stanford University, 
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Frederick Ehrenberg. Large 12mo. $2.00 net; by mail, $2.19. 

THE LIFE OF A FOSSIL HUNTER, by Charles H. Sternberg. 
Large 12mo. $1.60 net; by mail, $1.72. 

Arranged for; 

PHOTOGRAPHING NATURE, by E. R. Sanborn, Photographer 
of the New York Zoological Park. 

THE SHELLFISH INDUSTRIES, by James L. Kellogg, Profes¬ 
sor in Williams College. 

CHEMISTRY OF DAILY LIFE, by Henry P. Talbot, Professor 
of Chemistry in the Massachusetts Institute of Technology. 

DOMESTIC ANIMALS, by William H. Brewer, Professor 
Emeritus in Yale University. 

B. E. Fernow, Professor of Forestry, University of Toronto. 


This division will include a wide range of writings not rigidly 
systematic or formal, but written only by authorities of standing. 
Large 12mo. 5jx8§ in. 

AI ready publisht: 

INSECT STORIES, by Vernon L. Kellogg. $1.50 net; by mail, 

FISH STORIES, by Charles F. Holder and David Starr Jordan. 
Large 12mo. $1.75 net; by mail, $1.87. 

Arranged for; 

HORSE TALK, by William H. Brewer. 

BIRD NOTES, by C. W. Beebe. 


A Series of volumes by President Jordan, of Stanford Univer¬ 
sity, and Professors Brooks of Johns Hopkins, Lull of Yale, Thom¬ 
son of Aberdeen, Przibram of Austria, zur Strassen of Germany, 
and others. Edited by Professor Kellogg of Leland Stanford. 12mo. 
5$x7^ in. 


April, ’ 09 .