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EX. LIBRIS:

VHertram C. A. Mindle,
DS, MB, HSA.

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ustered round the Darwinian theory.
it was | lated. The author’s knowledge of his
sub eét is extensive, even encyclopedic and as a result of
his labours he has produced a work which will be of the
_ greatest value to all desirous of studying the present posi-
‘tion of the Darwinian theories, which, as he very carefully
points out, do not really involve the main thesis of trans-
-formism in any way. Especially useful are the excellent:
“appendixes to each chapter in which the literature of the
subject-matter of that chapter is surveyed and abstracted
| Lad many useful contributions to knowledge which have
appeared in publications not always easily accessible to
_ English readers are summarized and made available, As one
‘looks through these one cannot but be struck, however,
with the rapidity with which the situation changes as new
faéts come to knowledge. For example: Professor Vellog
holds that de Vries’ observations on Qeguthera LamarcWiana
are practically unchallengeable, yet, no doubt, since this.
book was written further observations on this point pub-
lished in the Journal of Botany have thrown the gravest
‘doubt upon them. But to return to the point under con-
sideration, what is the actual position of Darwinism to-day?
Some hold that it is on its deathbed (p. 1); another, and
thisa real. luminary'of science ( ch) writes: “ Darwinism
now belongs to history, like that other curiosity of our
century, the Hegelian philosophy; bothare variationsonthe
theme: how one manages to lead a whole generation by
the nose” (p. 6). On the other hand Lankester at York, in.
1906, proclaimed his belief “that the conclusions of Darwin.
as to the origin of species by the survival of selected
races in the struggle for existence are more firmly estab-
lished than ‘ever”’ (p. 389). :
_ Where such doctors differ and differ so fundamentally
“it is difficult for lesser mortals to form a judgement, and
Professor Vellog steers a middle course. He admits that’
“the discrediting of the sexual selection theory®”4$ an ex--
' planation of Secondary Sexual Characters “iscertainly nearly
complete” (p. 352), and he couples with it that other theory
of the pangenesis of ules, both of which are “nearly”
wholly discredited theories” (p. 3). | |
_ And with regard to the great theory of Natural Selection:
| hat “the fair truth is that the Darwinian selec

tion theories, considered with regard to their claimed capa-

iteniane factor in tape reo had hence as the sufficient ;
‘explanation of descent, is discredited and cast down, At ne again,
so it seems so me (p. 374).

- The evidence upon which this statement rests will be
ifound i in the book, and is well worthy of careful study by :
all those seriously ‘interested in biological matters. :

_ There is one further point to which attention must be
directed. The author gives us the views of men like Naeli.
and Korschinsky whose scientific evidence cannot be disba
ted and whose researches have led them to the conclusion
that there i is in organisms “an intrinsic tendency towards
progress,” “an inner law of development,” “an inner direc-
tive force” (p. 278) by which can be explained the deriva-_
tive of higher from lower forms. For views of this kind
and for those of the neo-vitalistic school our author has no.
sort of use. “Such a surrender of all our hardly won,
actual, scientific knowledge in favour of an unknown,
unproved, mystic vital force we are not prepared to make”
(p.2'78).And again, “Najeli’s automatic perfecting principleis
an impossibility to the pers evolutionist seeking
for a causo-mechanical explanation of change” (p. 387).

But why? Apparently because the “thorough-going evo-
lutionist”’ of this type assumes as a first principle that there
can be nothing in nature which is not explicable on chemico-
physical lines. Is such an assumption legitimate? No, is the
answer made by a large number of men whose eminence as
biologists cannot:be gainsaid. Professor Wellog speaks with
some scorn of papers written “by certain Roman Catholic
priests with a considerable amateur interest in natural ee
tory and a strong professional interest in anti-Darwinism”’
(p. 30). Is he, we ask him to. consider within hinheelf, |
wholly ignorant of certain scientific men witha considerable.
amateur interest in philosophy and a strong professional |
interest in anti-Vitalism? Science means or “should mean
the pursuit of truth, wherever it may lie, and since it is”
‘still possible that Najeli and others of like views, or even
‘the no doubt contemptible, though worthy, Roman
Catholic priests may be right and those on the other side.
wrong, would it not be well to abstain from coc sure
declarations until things are a little clearer-and ;
‘more certain. than: sav. ‘those. Darwinian » views.

_. OF THE DARWINIAN SELECTION THEORIES, TO-
Ss GETHER WITH A BRIEF ACCOUNT OF THE

ta.
a

PRINCIPAL OTHER PROPOSED AUXIL-
IARY AND ALTERNATIVE THEO-
RIES OF SPECIES-FORMING

VERNON L. KELLOGG

PROFESSOR IN LELAND STANFORD, JR., UNIVERSITY

LONDON

GEORGE BELL AND SONS
NEW YORK: HENRY HOLT AND COMPANY

1907]

Published August, 1907

AUG 19 1957

PREPACE,

Tuts book is written for the sake of presenting simply and
concisely to students of biology and to general readers the
present-day standing of Darwinism in biological science, and
to outline for them the various auxiliary and alternative
theories of species-forming which have been proposed to aid
or to replace the selection theories.

Our actual knowledge of the factors and mechanism of
organic evolution and our hypotheses and theories which
serve to fill in the present gaps in this knowledge have been
greatly added to and modified in the last few years. Much
that the general reader includes in his conception of organic
evolution, based on his reading of Darwin and Wallace and
Spencer, has been materially modified and some of it proved
untenable by modern investigation; while much which had
no place in this earlier general understanding of evolutionary
method and process may now be confidently added to it. The
present time is one of unprecedented activity and fertility
both in the discovery of facts and in attempts to perceive
their significance in relation to the great problems of bio-
nomics. Both destructive criticism of old, and synthesis of
new hypotheses and theories, are being so energetically car-
ried forward that the scientific layman and educated reader,
if he stand but ever so little outside of the actual working
ranks of biology, is likely to lose his orientation as to the
trend of evolutionary advance. Precisely at the present mo-
ment is this modification of the general point of view and
attitude of philosophical biologists unusually important and
far-reaching in its relation to certain long-held general con-
ceptions of biology and evolution. This modification of the
general trend of evolutionary thought must also necessarily

ili

iv PREFACE,

strongly affect our conceptions of the underlying principles
of such correlated sciences as sociology, pedagogy, etc. It
is, then, as a means of orientation in evolutionary matters for
the general reader and for the unspecialised but interested
student of science that this book is prepared.

That it may not be without some special usefulness to
more advanced students and biological workers there are
added, in appendices to the chapters, special notes (referred
to in the text by small super-numbers) in which are given
numerous exact references to general or special books or
papers, and accounts, in more or less detail, of particular
observations, experiments, or theoretical discussions, as well
as references to extended bibliographic lists of the subjects
under treatment. These notes will enable students, or others
interested, to look up the original sources of our knowledge
of the subjects of the various chapters, and to find more
detailed general or special discussions of them than can be
given in this book. These notes also enable the author to
introduce into the book some details of his own observations
and experiments touching various evolutionary subjects.

bom! Bee

STANFORD UNIverRsITY, /w“7é, 1907.

CONTENTS.

CHAPTERS.
INTRODUCTORY: THE ‘“DEATH-BED OF DAR.
WINISM” 7 , : ; ;
Modern cies in Bistoeic eudys . Darwinism not

synonymous with evolution, 3. Present-day anti-Darwin-
ism, 4. Intemperate anti-Darwinism, 6. Outline of this
“book, 7.

ApPpENDIx: Dennert’s intemperate attack on Darwinism,
7, An anti-evolution university biologist, 8. Friedmann’s
theory to replace evolution with divergence, 8.

CHATTER. ff,

DARWINISM AND EVOLUTION DEFINED AND

DISTINGUISHED j

Animal and plant kinds paetaats in one ie fares sees.
10. The theory of descent defined, 11. The theory of
descent given validity by Darwin’s explanation of the
cause of it, 12. Darwinism defined and analysed into its
fundamental assumptions and facts, 13. Sources of scien-
tific evidence for the theory of descent, 17. Relation of
theology, philosophy, pedagogy, and sociology to the
theory of descent, 20.

APPENDIX: Accounts of history of the descent theory,
22. Books giving the evidences for descent, 23. Dis-
cussions of the relation of descent and theology, 23.
Discussions of the relations of biology and philosophy, 24.
Biology and sociology, 24.

CHAPTER L171.

DARWINISM ATTACKED

The attack of the theologians, oe, The present-day
attack of the scientific men, 25. Some of the principal
objections to natural selection summarised, 30. Darwinian
or fluctuating variations too small to serve as ‘‘handles”

VV.

PAGE

CONTENTS.

for natural selection, 36. Many specific differences are
indifferent, z. ¢., not adaptive, 38. The extinguishing of
the extreme variations by interbreeding, 44. The im-
probability of the occurrence of the right variations at the
right time, 45. The difficulty of explaining the production
by natural selection of specialisations useful only in highly
complex condition, 49. The objection based on the over-
development of specialisations, 53. The objection based
on insufficient time, 54. The objection that natural selec-
tion tends to preserve the type rather than the variants,
and hence opposes change, 56,

AppENDIX: Books and papers on variation, 57. Cases of
marked variation in parthenogenetic animals, 58. Varia-
tion according to the law of probabilities, 59. Quetelet,
the discoverer of variation according tothe laws of chance,
61. Example of trivial variations, 62. Ndgeli’s seven
objections to species-forming by selection, 62. Wolff’s
attack on the selectionists’ assumption of the appearance
at the right time of the needed variation, 64. Example of
non-correlated variability in bilaterally repeated organs,
65. Henslow’s antagonism to selection as an explainer of
floral correlations, 67. Wolff’s objection to the necessary
assumption of identical and coincident variation in re-
peated structures, as feathers, scales, etc., 67. Example
of mal-adaption in the egg-laying habit of PAryganidia
californica, 68—Pieper’s antagonism to the selection ex-
planation of colour and pattern in insects, 69.

CHAPTER. Jt,

DARWINISM ATTACKED (Continued)

Objection to the exclusively linear or quantitative anee
acter of the fluctuating or Darwinian variations, 70.
Galton’s law of regression, 71. Selection may produce
evolution (continuous change) but not species (discontinu-
ous series), 73. Pfeffer’s objection based on the slowness
of species transformation, 75. The difficulty of explaining
the sterility of species by selection, 76. Selection cannot
explain extreme or complete degeneration of useless parts,
77. Objections to the assumed rigour of the struggle for
existence and to the actuality of intra-specific or personal
selection, 79. Indiscriminate extermination due to the

PAGE

fortune of position and time, 80. The necessity of sexual

CONTENTS. vil

PAGE.
_ selection, a discredited theory, for the support of the
natural selection theory, 85. Natural selection rests on an
unwarranted assumption of its homology with artificial
selection, 86. Many biologists find natural selection
unable to account for known biologic conditions, 89. Sig-
nificance of the concessions of Darwinians, go. Kor-
schinsky’s extreme anti-Darwinian doctrine, 91. Delage’s
“true réle of selection,” 93. Morgan’s rejection of natural
selection as a species-forming factor, 93.
APPENDIX: Galton’s statement of the law of regression,
97. Wolff's criticism of panmixia, 98. Example of inef-
fective panmixia, 100. Example of progressive degenera-
tion inexplicable by natural selection, 100. Wolff's
discussion of the selection coefficient, ror. Example of
non-selection of trivial differences, 103. References to
books and papers on plant breeding, 105.

CHAPTER VV.

DARWINISM ATTACKED (Continued): THE THEORY

OF SEXUAL SELECTION é : ‘ , : . 106
Secondary sexual differences or characters, 107. Classi- ;

fication of secondary sexual characters, 107. Useless and
harmful characters not explicable by natural selection,
110. Theory of sexual selection to account for them: the
theory defined, 111. Darwin’s assumptions as basis of the
theory of sexual selection, 112. Difficulties in the way of a
general application of the theory, 113. The theory appli-
cable only to species in which males are more numerous
than females, 113. The passivity of females, 114. Males
of species in which no real pairing occurs also show strik-
ing secondary sexual characters, 114. Necessity of
assuming unproved esthetic development among lower
animals, 114. Few recorded cases of observed choosing
by female, 115. Difficult to assume utility for many
secondary sexual characters, 115. Stolzmann’s case of the
Andean humming-birds, 116. Howexplain the beginnings
of secondary sexual characters, 117. How explain orna-
mental characters appearing in both males and females,
118. Morgan’s objections to sexual selection theory, 118.
Experimental evidence touching the theory is against it,
120. Mayer's experiments with Promethea and Porthetria
moths, 121. Douglass’s and Diirigen’s observations on

Vill

CONTENTS.

lizards, 123. Substitutionary theories of the origin of
secondary sexual characters, 124.

APPENDIX: References to books and papers discussing
sexual selection, 125. Wolff’s critical exposition of weak-
nesses in sexual selection, 126.

CHAPTER 11.

DARWINISM DEFENDED

Position of the defenders of Patines va Reaction
against the too speculative positions of Haeckel and
Weismann, 130. ‘‘Haeckelismus,” 130. Weismannism,
131. Struggle between Neo-Darwinians and Neo-La-
marckians, 133. Concessions of the Neo-Darwinians, 134.
Answer to objection concerning the too slight character of
fluctuating or Darwinian variations to serve as handles for
natural selection, 138. Answer to the objection concern-
ing the linear and quantitative character of Darwinian
variation, 139. Answer to the objection that selection can-
not produce many-branched descent, 142. Answer to the

statement that selection can produce continuous change

or evolution, but not species, 143. Answer to the objec-
tion concerning the production by selection of co-adaptive
and highly complex specialisations, 144. Answer to the

objection concerning the over-development of specialisa-

tions, 146. Discussion of the difficulty that natural selec-
tion has with structural degeneration, 146. The Darwinian

answer to the expressions of doubt about the rigour of

selection, 148. Answer to the objections to the sexual
selection theory, 148. Discussion of the objection to the
derivation of evidence for natural selection from the facts
of artificial selection, 150. Tayler’s general defence, 153.

APPENDIX: Weldon’s experiments on Carcinus, 158.
Tayler’s explanation of degeneration by natural selection,
162. Plate’s explanation of character fixity in domestic
animals, 163.

CHAPTER VII.

DARWINISM DEFENDED (Continued): PLATE’S CON.

CILIATORY DEFENCE :

Plate, afair-minded Darwinian sheen aie 164. Aaawers
to the objection based on the slight character and inutility
of Darwinian variations, 165. Many slight differences at

PAGE

129

164

CONTENTS. ix

. PAGE
| first glance apparently indifferent in character found on

more careful inspection to be of advantage, 166. Slight
characters aided by co-related differences, 167, The prin-
ciple of the change of function, 168. Characters of in-
different value under one condition of environment,
suddenly made important by a change in life-conditions,
169. Organs of universal character which can become
modified in various directions, 169. Lamarckian factors
called to the aid of Darwinism, 170. Answers to the
objection based on the improbability of the appearance of
the right variations at the right time for the progressive
perfecting or development of an organ, 170. Selection
directs itself according to variation, not variation accord-
ing to any assumed needs of selection, 171. Selection
works with plural variations, not single ones, 172. The
same selective value can often be attained through combi-
nations of various peculiarities and the same effect
reached by various means, 172. The element of chance
_ not peculiar to the Darwinian explanation of co-adap-
tations, 175. Answers to the objection based on the
assumed improbability that during the course of the
development of a complex organ or whole body-part, or
during the perfecting of a changing adaptation the
numerous necessary adaptations will occur in such a suc-
cessive series as to make possible any harmonious correla-
tion of the various single variations, 176. Plate’s reliance
on the Lamarckian factor of the inheritance of characters
acquired through use, disuse, and other functional stimuli,
178. The attainment of selective value by various means,
178. Weismann’s theory of germinal selection unaccept-
able, 180. Weismann’s principle of amphimixis of great
importance, 180. The necessity of concessions admitted
181. The necessity of invoking auxiliary or aiding prin-
ciples to support the natural selection theory, 182.
APPENDIX: Conn’s discussion of selective value, 182.
References to papers on correlation, 184. Cope’s proof
that natural selection cannot originate new characters, 185.

CHAPTER: V 117.

OTHER THEORIES OF SPECIES-FORMING: THEO-
RIES AUXILIARY TO SELECTION . ; . 187

The presentation of theories to aid the selection theories

or others to replace them really a continuation of the

x CONTENTS.

PAGE
defence of, and attack on, Darwinism, 187. The Weis-

mannian theories, 188. Panmixia, 190. The theory of
germinal selection, 193. The physical and chemical
structure of protoplasm, 194. Objections to the theory
of germinal selection, 200. Roux’s theory of intra-selec-
tion, or the battle of the parts, 201. Objections to Roux’s
theory, 203. The theory of organic selection, or ortho-
plasy, 208.

APPENDIX: List of Weismann’s evolution papers, 212.
Theories of ultimate protoplasmic structure, 214. Encase-
ment theory, 215. Micromeric theories, 215. Buffon's
theory, 216. Spencer’s theory, 217. Darwin’s theory,
218. Nadageli’s theory, 219. De Vries’s theory, 220. Hat-
schek’s theory, 222. Delage’scriticisms, 224. Le Dantec’s
criticisms, 224. Verworn’s biogen hypothesis, 225. De-
lage’s machine theory, 225. Le Dantec’s theory of
chemism, 225. Neo-vitalism, 226. Morgan’s criticism of
Weismann’s method of argument, 229. References to
discussions of orthoplasy, 229.

CHAL IER IX,

OTHER THEORIES OF SPECIES-FORMING (Continued):
THEORIES AUXILIARY TO SELECTION (Continued) 232

Isolation theories, 232. Wagner’s ‘‘Separations-theorie,”
234. Jordan’s upholding of the importance in species-
forming of geographic isolation, 237. Biologic and sexual
isolation, or physiological selection, 243. Gulick’s work
and conclusions, 249.

APPENDIX: References to discussions of isolation, 253.
Haacke’s summary of Wagner’s theory, 253. Grinnell’s
studies of geographic differences in the chickadee, 255.
Further references to discussions of isolation, 261.

CHAPTER A,

OTHER THEORIES OF SPECIES-FORMING (Con-
tinued): THEORIES ALTERNATIVE TO SELEC-
TION ‘ 3 ; 3 : : ; : ol Aas « 262

Three general groups of theories proposed to replace the
selection theories as explanations of species-forming and
evolution, 262. The Lamarckian theory, 262. Objections
to the Lamarckian factors, especially that of the inheritance

CONTENTS. 4

PAGE
of acquired characters, 266. Great use could be made of

the Lamarckian factors in explaining evolution phenomena
if these factors could be given validity, 271. Orthogenesis
and determinate variation, pointing toward orthogenesis,
271. Niageli’s theory of orthogenesis, 277. Eimer’s ortho-
genetic theory, 282. Cope’s theory of bathmism and
kinetogenesis, 285. Jaeckel’s theory of metakinesis, 289.

APPENDIX: Referencesto Lamarck’s writings, 290. Brown-
Séquard’s experiments on guinea pigs, 290. Hyatt’s
studies of P/anorbis, 295. Fischer’s experiments with
butterflies, 296. Experiments with silkworms, 298. Ref-
erences to books and papers on inheritance of acquired
characters, 305. Redfield’s position, 305. Montgomery’s
explanation of inheritance of variation, 306. Scientific
aspects of Burbank’s work, 310. Orthogenetic variation
in paleontology, 319. A case of apparent determinate
variation, 319. Pfeffer’s theory of orthogenesis, 320.
Eimer’s theory of orthogenesis, 321. Apparent determi-
nate evolution, 322. Snodgrass’s observances on bills of
Galapagos birds, 323. Cope’s belief in orthogenetic evolu-
tion, 323. Whitman’s belief in determinate variation, 325.
Cunningham and orthogenesis, 326.

CAAT LR AT.

OTHER THEORIES OF SPECIES-FORMING (Con-
tinued); THEORIES ALTERNATIVE TO SELEC-
TION (Contenued) : ‘ : ~ 927

Heterogenesis or the riittations dicey. se "eae
tions of heterogenesis theories by von Kolliker, Dall,
Galton, and Emery, 330. Korschinsky’s heterogenesis
theory, 333. De Vries’s mutations theory, 337. Present
status of de Vries’s theory, 348. Alternative theories to
explain secondary sexual characters, 352.

APPENDIX: Mendel and his work, 356. References to
recent work on Mendelism, 357. Darwin's examples of
race origin from sports, 357. A recent example of race
origin from a sport in cattle, 358. Galton’s discussion of
specific stability, 360. References to discussions by de
Vries of species-forming, 362. American opinions of the
mutations theory, 362. Davenport’s example of species
origin by slight continuous change, 367. Merriam’s criti-
cism of the mutations theory, 367. Plate’s criticism of the

Xii

CONTENTS.

mutations theory, 368. References to theories explaining
secondary sexual characters, 373.

CHAP IL AT,

DARWINISM’S PRESENT STANDING

Natural selection the final control in evolution, but not
a sufficient explanation of species-forming, 374. Weak-
nesses of the substitutionary theories, 375. The unknown
factors of evolution, 377. Prime needs of evolution study;
first, the intensive study, statistical and experimental, of
variability, 378. Second, the means of cumulating varia-
bility along definite lines, 379. Third, the investigation of
adaptation, 380. A suggested argument for a belief in the
transference of ontogenic changes into phylogeny, 382. A
suggested automatic causal factor of variability, purposive
but not purposeful, 384. Our present ignorance and the
call to work, 387.

AePENDIX: Wigand’s criticism of the selection theories,
387. Lankester’s upholding of Darwinism, 389. De Vries’s

discussion of species-forming by selection, 389. Delage’s

estimate of selection, 390. Osborn’s championship of the
unknown factors of evolution, 391. Klebs’s ‘conclusions
from experiments on plants, 392. Friedlander’s discussion
of adaptation, 392. Loeb’s attitude toward the problem of
species-forming, 393.

INDEX a oe ae ee ee a

PAGE

374

397

DARWINISM TO-DAY

MO ae a a

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DARWINISM TO-DAY.

CHAPTER I.

INTRODUCTORY :-fHE-"DEATH-BED OF
DARWINISM.”

“Vom STERBELAGER DES DarRwinisMus!” This is the
title of a recent pamphlet * lying before me. But ever since
there has been Darwinism there have been occasional death-
beds of Darwinism on title pages of pamphlets, addresses,
and sermons. Much more worth consideration than any
clerical pamphlets or dissertations, under this title, by frisch-
gebackenen German doctors of philosophy—the title alone
proving prejudice or lack of judgment or of knowledge—
are the numerous books and papers which, with less sensa-
tional headlines but infinitely more important contents, are
appearing now in such numbers and from such a variety of
reputable sources as to reveal the existence among biologists
and philosophers of a widespread belief in the marked
weakening, at least, if not serious indisposition, of Darwin-
ism. A few of these books and papers from scientific sources
even suggest that their writers see shadows of a death-bed.

The present extraordinary activity in biology is two-
phased; there is going on a most careful re-examination or

Modern activ. Scrutiny of the theories connected with organic
ity in biologic evolution, resulting in much destructive criti-
ae: cism of certain long-cherished and widely held
beliefs, and at the same time there are being developed and
almost feverishly driven forward certain fascinating and
fundamentally important new lines, employing new methods,

ees

2 DARWINISM TO-DAY.

of biological investigation. Conspicuous among these new
kinds of work are the statistical or quantitative study of
variations and that most alluring work variously called
developmental mechanics, experimental morphology, ex-
perimental physiology of development, or, most suitably of
all because most comprehensively, experimental biology.’
This work includes the controlled modification of conditions
attending development and behaviour, and the pedigreed
breeding of pure and hybrid generations. Now this combina-
tion of destructive critical activity and active constructive ex-
perimental investigation has plainly resulted, or is resulting,
in the distinct weakening or modifying of certain familiar
and long-entrenched theories concerning the causative factors
and the mechanism of organic evolution. Most conspicuous
among these theories now in the white light of scientific
scrutiny are those established by Darwin, and known, col-
lectively, to biologists, as Darwinism.

To too many general readers Darwinism is synonymous
with organic evolution or the theory of descent. The word
is not to be so used or considered. Darwinism,
primarily, is a most ingenious, most plausible,
and, according to one’s belief, most effective or
most inadequate, causo-mechanical explanation of adaptation
and species-transforming. It is that factor which, ever since
its proposal by Darwin in 1859, has been held by a majority
of biologists to be the chief working agent in the descent,
that is, the origin, of species. However worthy Darwin is of
having his name applied directly to the great theory of
descent—for it was only by Darwin’s aid that this theory,
conceived and more or less clearly announced by numerous
pre-Darwinian naturalists and philosophers, came to general
and nearly immediate acceptance—the fact is that the name
Darwinism has been pretty consistently applied by biologists
only to those theories practically original with Darwin which
offer a mechanical explanation of the accepted ‘fact of

What Dar-
winism is,

a
- +
SS

INTRODUCTORY: “DEATH-BED OF DARWINISM.” 3

descent. Of these Darwinian theories the primary and all-
important one is that of natural selection. Included with
this in Darwinism are the now nearly wholly discredited

theories of sexual selection and of the pangenesis of gem- |

mules. It may also be fairly said that the theory of the
descent of man from the lower animals should be included in
Darwinism, For Darwin was practically the first naturalist
bold enough to admit the logical and obvious consequences
of the general acceptance of the theory of descent, and to
include man in the general chain of descending, or ascend-
ing, organisms. So that the popular notion that Darwinism
is in some way the right word to apply to the doctrine that
man has come from the monkeys is rather nearer right than
wrong. But biologists do not recognise the descent of man
as a special phase of Darwinism, but rather of the whole
theory of descent, or organic evolution.
Darwinism, then, is not synonymous with organic evolu-
tion, nor with the theory of descent (which two phases are
a used by the biologist practically synonymously ).
Darwinism
not synonymous 9Lherefore when one reads of the “death-bed of
with evolution. Parwinism,” it is not of the death-bed of or-
ganic evolution or of the theory of descent that one is read-
ing. While many reputable biologists to-day strongly doubt
the commonly reputed effectiveness of the Darwinian selec-

tion factors to explain descent—some, indeed, holding them |

to be of absolutely no species-forming value—practically
no naturalists * of position and recognised attainment doubt
the theory of descent.“ Organic evolution, that is, the
descent of species, is looked on by biologists to be as proved
a part of their science as gravitation is in the science of
physics or chemical affinity in that of chemistry. Doubts
of Darwinism are not, then, doubts, of organic evolution.
Darwinism might indeed be on its death-bed without shaking
in any considerable degree the confidence of biologists and
natural philosophers in the theory of descent.

Li ln SII DT ae

4 DARWINISM TO-DAY.

But the educated reader, the scientific layman, the thinker
and worker in any line of sociologic, philosophic, or even
theologic activity is bound to be disturbed and
Present-day

anti-Darwin- unsettled by rumours from the camp of pro-
ae fessional biologists of any weakness or mortal
illness of Darwinism. We have only just got ourselves and
our conceptions of nature, of sociology and philosophy, well
oriented and adjusted with regard to Darwinism. And for
relentless hands now to come and clutch away our founda-
tions is simply intolerable. Zim Teufel with these German
professors! For it is precisely the German biologists who
are most active in this undermining of the Darwinian
theories. But there are others with them; Holland, Russia,
Italy, France, and our own country all contribute their
quota of disturbing questions and declarations of protest
and revolt. The English seem mostly inclined to uphold
the glory of their illustrious countryman. But there are
rebels even there. Altogether it may be stated with full
regard to facts that a major part of the current published
output of general biological discussions, theoretical treatises,
addresses, and brochures dealing with the great evolutionary
problems, is distinctly anti-Darwinian in character. This
major part of the public discussion of the status of evolution
and its causes, its factors and mechanism, by working
biologists and thinking natural philosophers, reveals a
lack of belief in the effectiveness or capacity of the natural
selection theory to serve as a sufficient causo-mechanical
explanation of species-forming and evolution. Nor is this
preponderance of anti-Darwinian expression in current
biological literature to be wholly or even chiefly attributed
to a dignified silence on the part of the believers in selection.
Answers and defences have appeared and are appearing.
But in practically all these defences two characteristics are
to be noted, namely, a tendency to propose supporting
hypotheses or theories, and a tendency to make certain

INTRODUCTORY: “DEATH-BED OF DARWINISM.” = 5

distinct concessions to the beleaguering party. The fair
truth is that the Darwinian selection theories, considered
with regard to their claimed capacity to be an independently
sufficient mechanical explanation of descent, stand to-day
seriously discredited in the biological world. On the other
hand, it is also fair truth to say that no replacing hypothesis:
or theory of species-forming has been offered by the oppo-
nents of selection which has met with any general or even
considerable acceptance by naturalists. Mutations seem to:
be too few and far between; for orthogenesis we can dis-
cover no satisfactory mechanism; and the same is true for
the Lamarckian theories of modification by the cumulation,.
through inheritance, of acquired or ontogenic characters.
Kurz und gut, we are immensely unsettled.

Now but little of this philosophic turmoil and wordy
strife has found its way as yet into current American litera-
ture. Our bookshop windows offer no display, as in Ger-
many, of volumes and pamphlets on the newer evolutionary
study ; our serious-minded quarterlies, if we have any, and
our. critical monthlies and weeklies contain no debates or
discussions over “das Sterbelager des Darwinismus.” Our’ |
popular magazines keep to the safe and pleasant task of
telling sweetly of the joys of making Nature’s acquaintance
through field-glasses and the attuned ear. But just as cer-
tainly as the many material things “made in Germany” have
found their way to us so will come soon the echoes and
phrases of the present intellectual activity in evolutionary
affairs, an activity bound to continue as long as the new
lines of biological investigation continue their amazing out-
put of new facts to serve as the bases for new critical attacks
on the old notions and for the upbuilding of new hypotheses.
If now the first of these echoes to come across the water
to us prove to be, as wholly likely, those from the more vio-
lent and louder debaters, they may lead to an undue dismay
and panic on our part. Things are really in no such desper-

6 DARWINISM TO-DAY.

ate way with Darwinism as the polemic vigour of the Ger-
man and French anti-Darwinians leads them to suggest.
Says one of them: “Darwinism now belongs to history,
like that other curiosity of our century, the
| Hegelian philosophy ; both are variations on the
theme: how one manages to lead a whole gen-
eration by the nose.” The same writer also speaks of “the
softening of the brain of the Darwinians.’’ Another one,’ in
similarly relegating Darwinism to the past, takes much pleas-
ure in explaining that “we [anti-Darwinians] are now stand-
ing by the death-bed of Darwinism, and making ready to
send the friends of the patient a little money to insure a
decent burial of the remains.’” No less intemperate and in-
decent is Wolff’s " reference to the “episode of Darwinism”
and his suggestion that our attitude toward Darwin should
be “‘as if he had never existed.” Such absurdity of ex-
pression might pass unnoticed in the mouth of a violent
non-scientific debater—let us say an indignant theologian
of Darwin’s own days—but in the mouth of a biologist of
recognised achievement, of thorough scientific training and
unusually keen mind—for this expression came from just
such a man—it can only be referred to as a deplorable
example of those things that make the judicious to grieve.
Such violence blunts or breaks one’s own weapons.

While I have said that the coming across the water of
the more vigorous anti-Darwinian utterances might cause
some dismay and panic in the ranks of the educated reader—
really unnecessary panic, as I hope to point out—it will
doubtless occur to some of my readers to say that this fear
of panic is unwarranted. If the first phrases to come are
as injudicious and intemperate, hence as unconvincing, as
those just cited, the whole anti-Darwinian movement will
be discredited and given no attention. Which, I hasten to
reply, will be as much of a mistake as panic would be.
There is something very seriously to be heeded in the

INTRODUCTORY: “DEATH-BED OF DARWINISM.” 7

chorus of criticism and protest, and wholly to stop one’s
ears to these criticisms is to refuse enlightenment and to
show prejudice. I have thought it, therefore, worth while

to try to anticipate the coming of fragmentary
PE icery of and disturbing extracts from the rapidly in-

creasing mass of recent anti-Darwinian litera-
ture by presenting in this book a summary account not alone
of these modern criticisms, but of the answers to them by the
steadfast Darwinians, and of the concessions and supporting
hypotheses which the supporters of both sides have been led
to offer during the debates. I shall try to give a fair state-
ment of the recent attacks on, and the defence and present
scientific standing of, the familiar Darwinian theories, and
to give also concise expositions, with some critical comment,
of the more important new, or newly remodelled alternative
and auxiliary theories of species-forming and descent, such
as heterogenesis, orthogenesis, isolation, etc., and an esti-
mate of their degree of acceptance by naturalists.

APPENDIX.

1Dennert, E., “Vom Sterbelager des Darwinismus,” Stuttgart,
1903. An intemperate and unconvincing but interesting brief against

Dennert’sin- the Darwinian factors, 1. e., the selection theories, in
temperate attack evolution. Author fully accepts the theory of descent,
on Darwinism: byt in no degree the Darwinian causal explanation of
this descent. “‘Was ich in diesen Berichten nachzuweisen suche,
ist die Tatsache, dass der, Darwinismus nunmehr bald der Ver-
gangenheit, der Geschichte angehort, dass wir an seinem Sterbe-
lager stehen und dass auch seine Freunde sich eben anschicken,
ihm wenigstens noch ein anstandiges Begrabnis zu sichern” (p. 4).
The valuable thing about the paper is that it is largely given to a
gathering together of the anti-Darwinian opinions and declarations
of numerous, mostly well-known and reputably placed biologists.
Some of these declarations are interpreted by Dr. Dennert in a way
that would probably hardly be wholly acceptable to the declarers, but
for the most part the anti-Darwinian beliefs of these biologists are
uumistakably revealed by their own words. Among the biologists
and biological philosophers thus agglomerated into the camp of

8 DARWINISM TO-DAY.

anti-Darwinism are Wigand, Haacke, von Sachs, Goette, Kor-
schinsky, Haberlandt, Steinmann, Eimer, M. Wagner, von Kolliker,
Nageli, Kerner, F. von Wagner, Fleischmann, O. Schultze, O. Hert-
wig, and others. This list includes reputable botanists, zoologists,.
and paleontologists.

? For a recent account of such work, see Morgan, T. H., ‘“Experi-.
mental Zodlogy,” 1907.

* A. Fleischmann, professor of zoology in the University of Er-
langen, is the only biologist of recognised position, of whom I am

An anti-evolu- aware, who publicly declares a disbelief in the theory
tion university of descent. He seems to base his disbelief on the
diologist. fact that the phyletic (genealogic) series in numerous.
animal groups are as yet unexplained. See his book, “Die De-
scendenztheorie,”’ Leipzig, 1901. ‘‘Allein je mehr ich mich in die
vermeintlichen Beweisgriinde derselben [the theory of descent]
vertiefte und durch Spezialuntersuchungen positive Anhaltspunkte
fur die Stammesverwandtschaft der Tiere zu gewinnen suchte, um
so klarer stellte sich mir die Erkenntniss heraus, dass jene Theorie
eben doch mehr nur ein bestrickender, Ergebnisse und Aufklarung
vortauschender Roman sei, als eine auf positiven Grundlagen auf-
gebaute Lehre.” (From the preface of this book).

*A curious attempt to formulate a scientific theory explaining
the conditions as we know them in the world of life, to replace the

Friedmann’s theory of descent, is contained in a recent small book
theory to replace called “Die Konvergenz der Organismen” (1904),
evolution with by Hermann Friedmann, The author assumes that the
divergence. diversity of organisms is the primary condition, and
that their similarity has been brought about through convergence, as
opposed to the postulate of the theory of descent to the effect that
diversity of life has grown out of primary identity or homogeneity.
I quote (p. 12) as follows from Friedmann: “‘Diese Annahme, die in
dem vorliegenden Buch vertreten wird, ist folgendermassen zu erlau-
tern. Wir gehen von dem Hauptsatze aus, dass das Leben immer als
ein bestimmter, unwandelbarer Speziescharakter auftritt. Die spezi-
fisch verschiedenen Lebensformen erscheinen jedoch einander
angenahert, bezw. annaherbar, durch drei (Teil-) prinzipien, von
denen das Leben beherrscht wird: Das Prinzip, vermoge dessen
spezifisch verschiedene Formen solche Ubereinstimmungen auf-
weisen, die wir als primargesetzliche betrachten, nennen wir das
Prinzip der Homologie; als einen Ausfluss des Prinzips der Analo-
gie bezeichnen wir diejenigen Ubereinstimmungen, die unter dem
Einfliisse gleichwirkender dusserer (mittelbar oder unmittelbar
bewirkender oder selektiver) Bedingungen entstehen; und wir
erkennen drittens die Macht und die Tragweite eines Prinzips der

INTRODUCTORY: “DEATH-BED OF DARWINISM.” .- >

direkten Konvergenz, welches das Entstehen von Ubereinstim-
mungen zwischen den Genossen einer Biosphare aus psychischen
Ursachen bewirkt. Die drei Prinzipien bilden die Grundlage der
Konvergenztheorie.”

* Driesch, H., Biolog. Centralb., v. 16, p. 355, 1896.

* Dennert, E., ““Vom Sterbelager des Darwinismus,” p. 4, 1903.

7 Wolff, G., ‘“Beitrage zur Kritik der Darwin’schen Lehre,” p. 54,

1808.

CHAPTER: it;

DARWINISM AND EVOLUTION DEFINED AND
DISTINGUISHED.

Our manuals of zoology and botany contain the names
and descriptions of about 400,000 living species of animals
and 200,000 living species of plants. There are
Possible = parts of the earth from which we have collected
modes of origin ; P
of diverse plant as yet only a few kinds of animals and plants,
scabs merely the larger, more conspicuous or more
abundant kinds; there are no parts of the earth
from which we are not constantly receiving reports of the
discovery of “new” species—new, of course, simply in the
sense that we have not known them before. It is wholly
certain that the number of different species, that is, kinds,
of living organisms must number millions; various guesses,’
all unimportant, have been made. Of the extinct species,
those hosts of strange denizens of our changing earth in the
ages gone, the number of recorded forms can at best be but
the veriest fraction of the grand total of species that have
actually existed. Now all these millions of kinds of animals
and plants can have had an origin in some one of but three
ways; they have come into existence spontaneously, they \
have been specially created by some supernatural power, or (
they have descended one from the other in many-branching |
series by gradual transformation. There is absolutely no
scientific evidence for either of the first two ways; there is
much scientific evidence for the last way. There is left for
the scientific mdn, then, solely the last; that is, the method
Ge)

DARWINISM AND EVOLUTION DEFINED. . I1

of descent. The theory of descent (with which phrase or-
ganic evolution may be practically held as a synonym) is,
then, simply the declaration that the various
living as well as the now extinct species of
organisms are descended from one another and
from common ancestors. It is the explanation of the origin
of species accepted in the science of biology. (The natural

Theory of
descent defined,

question about the first species or the first several, if they
appeared simultaneously, will receive attention later; the |

theory of descent explains the origin of kinds of life, not
the origin of life.) If such a summary disposal of the
theories of spontaneous generation and divine creation is too
repugnant to my readers to meet with their toleration, then,
as Delage has pertinently said in connection with a similar
statement in his great tome on “Heredity,” my book and such
readers had better immediately part company; we do not
speak the same language.

The theory of descent, long before it was fully set forth
by Darwin in 1858 together with a definite and wholly

Pre-Darwin. Plausible causo-mechanical ‘explanation of it,
jan recognitio had been foreshadowed and even fairly ex-
ofdescent, —plicitly formulated by various philosophical
naturalists; among others, Goethe (1790) in Germany,
Erasmus Darwin (1794) (grandfather of Charles Darwin)
in England, Lamarck (1809) very definitely in France,
Chambers in the ‘“Vestiges of the Natural History of
Creation” (1844), and Wallace (1858) coincidently with
Darwin himself had all recognised descent as the only pos-
sible scientific explanation of the origin of spécies and had
offered explanations of the causal factors of this descent.
Even in the far older writings * of the Greeks, most con-
spicuously perhaps in the pages of Aristotle (350), may be
found phrases and pages foreshadowing those of Lamarck,
Wallace, and Darwin. But it was not until Darwin had
‘backed up the formulation of the descent theory with that

L2 DARWINISM TO-DAY.

wonderful accumulation of illuminating and explaining —
facts, and with those always ingenious but ever candid and
supremely honest tryings-on of the theory to the various.
fact-bodies, that the Theory of Descent began
Theory of to be spelled with capital letters in the biological
carrie tag creed. Nor was it merely good-fortune that
Darwin. led to the quick and wide acceptance of the
theory of descent when proposed by Darwin,
while the same theory when proposed twenty years earlier by
Lamarck found practically only rejection. It was because
to the old descent theory the new Darwinian theories were
added. It was because of that explaining Darwinism, which
to-day is being so rigorously re-examined as to its validity,
that the theory of descent took its definite place as the
dominant declaration in the biological credo.

This Darwinism of 1858 and 1859 consisted of the selec-
tion theories; the Darwinian pangenesis of gemmules theory
was a product of ten years later. It was the first of the
Darwinian concessions to scientific anti-Darwinism. That
is, it was a supporting hypothesis erected to strengthen a
foundation which was being weakened by the enemy’s
attacks. Curiously enough this first Darwinian concession
was made not on behalf of a true Darwinian principle, but
for the sake of a Lamarckian principle which Darwin had
thought necessary to include in his general conception of the
transmission of variations. Even in the formulation of the
true Darwinism, the selection theories, there must also be
recognised the participation of other minds than that of
Darwin. Malthus, who wrote, in 1826, of the over-supply
and the consequent struggle in the human population and
undoubtedly added much to Darwin’s confidence in his own
conception of the prodigality of production and the necessary
struggle for life throughout the world of organisms, and
Wallace, who came to conclusions practically identical with
Darwin’s at practically the same time, are men whose names

DARWINISM AND EVOLUTION DEFINED. i

are ever to be associated with the theory of over-production,
struggle, and selection.

Darwinism may be defined, hen, as a certain rational,
causo-mechanical (hence, non-teleologic) explanation of the

The Dar- origin of new species. The Darwinian explana-
‘winian expla- : . :
nation ofde. 10m rests on certain observed facts, and certain
‘scent, inductions from these facts. The observed

facts are: (1) the increase by multiplication in geometrical
ratio of the individuals in every species, whatever the kind
of reproduction which may be peculiar to each species,
whether this be simple division, sporulation, budding, par-
thenogenesis, conjugation and subsequent division, or
amphimixis (sexual reproduction) ; (2) the always apparent
slight (to greater) variation in form and function existing
among all individuals even though of the same generation or
brood; and (3) the transmission, with these inevitable
‘slight variations, by the parent to its offspring of a form
and physiology essentially like the parental. The inferred
(also partly observed) facts are: (1) a lack of room and
food for all these new individuals produced by geometrical
multiplication and consequently a competition (active or
passive) among those individuals having any cecologic rela-
tions to one another, as, for example, among those occupying
the same locality, or needing the same food, or needing each
other as food; (2) the probable success in this competition
of those individuals: whose slight differences (variations)
are of such a nature as to give them an advantage over their
confreres, which results in saving their life, at least until
they have produced offspring; and (3) the fact that these
“saved” individuals will, by virtue of the already referred
to action of heredity, hand down to the offspring their
advantageous condition of structure and physiology (at
least as the ‘““mode” or most abundantly represented condi-
tion, among the offspring).

The competition among individuals and kinds (species)

14 DARWINISM TO-DAY.

of organisms may fairly be called a struggle. This is
obvious when it is active, as in actual personal
eee and pattling for a piece of food or in attempts to
capture prey or to escape capture, and less
obvious when it is passive, as in the endurance of stress of
weather, hunger, thirst, and untoward conditions of any
kind. The struggle is, or may be, for each individual
threefold in nature: (1) an active struggle or com-
petition with other individuals of its own kind for
space in the habitat, sufficient share of the food, and
opportunity to produce offspring in the way peculiar and
common to its species; (2) an active or passive struggle or
competition with the individuals of other species which may
need the same space and food as itself, or may need it or
its eggs or young for food, and (3) an active (or more
usually passive) struggle with the physico-chemical external
conditions of the world it lives in, as varying temperature
and humidity, storms and floods, and natural catastrophes
of all sorts. For any individual or group of individuals any
of these forms of struggle may be temporarily ameliorated,
as is (1) the intra-specific struggle among the thousands of
honey-bee individuals living together altruistically in one
hive, or (2) the inter-specific struggle when two species
live together symbiotically as the hermit crab * Eupagurus
and the sea-anemone Podocoryne, or (3) the struggle
against untoward natural conditions as in special times or
places of highly favourable climate, etc. Or for any indi-
vidual or group of individuals all forms of the struggle may
be coincidently active and severe. The resultant of these
existing conditions is, according to Darwin and his followers,
an inevitable natural selection of individuals and of species. ,
Thousands must die where one or ten may live to maturity '
(1. e., to the time of producing young). Which ten of the
thousand shall live depends on the slight but sufficient ad-
vantage possessed by ten individuals in the complex struggie |

DARWINISM AND EVOLUTION DEFINED. 15

for existence due to the fortuitous possession of fortunate
congenital differences (variations). The nine hundred and
ninety with unfortunate congenital variations are extin-
guished in the struggle and with them the opportunity
for the perpetuation (by transmission to the offspring) of
their particular variations. There are thus left ten to re-
produce their advantageous variations. The offspring of
the ten of course will vary in their turn, but will vary around

—s-

the new and already proved advantageous parental condi- |

tion: among the thousand, say, offspring of the original
saved ten the same limitations of space and food will again
work to the killing off before maturity of nine hundred and
ninety, leaving the ten best equipped to reproduce. This
repeated and intensive selection leads to a slow but steady
and certain modification through the successive generations
of the form and functions of the species; a modification
always towards adaptation, towards fitness, towards a
moulding of the body and its behaviour to safe conformity
with external conditions. The exquisite adaptation of the
parts and functions of the animal and plant as we see it
every day to our infinite admiration and wonder has all
come to exist through the purely mechanical, inevitable

weeding out and selecting by Nature (by the environmental |

determining of what may and what may not live) through
uncounted generations in unreckonable time. This is Dar-
win’s causo-mechanical theory to explain the transformation
of species and the infinite variety of adaptive modification.
A rigorous automatic Natural Selection is the essential idea
in Darwinism, at least in Darwinism as it is held by the
present-day followers of Darwin.

What auxiliary and supporting factors Darwin considered
possibly or certainly of some influence or effect in species-

Artificial forming we may postpone reference to until
selection. our more particular examination of the natural
selection theory in succeeding chapters of this book. Simi-

16 DARWINISM TO-DAY.

larly we may postpone any immediate reference to the facts
of Artificial Selection (so important in any account of Dar-
winism), that process, more or less familiar to us all,
whereby the plant and animal breeders quickly and exten-
sively modify the particular species with which they deal so
as to produce, to order, as it were, manifold new kinds
(races) of organisms. Despite the complexity of methods
used in artificial selection, due to the combining of hybrid-
isation, direct modification by varying nutrition, grafting,
budding, etc., with selection, the basic and all-important
essential is the selecting of a few individuals, namely, those
which show the desired variations, to live long enough to
produce offspring, and the killing out before maturity of the
thousands of individuals that show unfortunate variations :
(unfortunate, that is, from the breeder’s point of view).
In the gardens of that extraordinary plant-breeder, Luther
Burbank, in California, great bonfires of discarded seedlings
correspond to the succumbing of the thousands in field and
forest in the natural struggle for existence, while tenderly
cared for little rows of pots contain the fortunate few which
have withstood the rigours of the artificial competition.
A part of Darwinism, which has already been named as
such, is the theory of Sexual Selection; but the details of
this, too, we may leave unexplained for the
moment in order not too much to trouble the
reader and the author, whose aim just now is
to define the essential thought or conception in Darwinism,
and to distinguish between this essential Darwinism and
the different and wholly independent theory of descent.
Sexual selection is one of Darwin’s supporting theories
which has nearly gone quite by the board. It is based on a
postulated particular and limited kind of natural selection,
not involving determination between life and death, but a
determination between going childless and leaving posterity,
—which is, after all, the essential determination in general

Sexual se-
lection.

DARWINISM AND EVOLUTION DEFINED. be

natural selection. But the assumed choice in the theory
of sexual selection has a much less mechanical and auto-
matically working basis, involves violent assumptions re-
garding the esthetic development of birds, butterflies, and
spiders, and as we shall later see was one of the first of Dar-
winian outworks to be sadly breached by attack.
I hope now to have pointed out clearly in the preceding
paragraphs the real distinction between the theory of
descent and the theory of natural selection
Theory ofde- (Darwinism). The bases, consisting of ob-
scent and the ;
theory ofnatural served facts and logical reasons, of the selec-
og tion theory, have been given; perhaps it were
well to state briefly the bases, or sources of the
scientific evidence for the theory of descent. This evi-
dence is derived from three chief sources; the study of the
comparative anatomy and structural homologies of organ-
isms, the study of the prehistoric animals and plants, that
is, paleontology or historical geology, and the study of
ontogeny, or embryology, that is, the development of in-
dividual animals and plants. The homologies or structural
correspondence, in gross and in detail, which the study of
animal and plant comparative anatomy reveals to exist in
varying degrees among living and extinct kinds of organ-
isms have but one possible scientific explanation : an explana-
tion which serves at once to account for the existence of
this correspondence and for its varying degrees.
| Pesta ata for This explanation is community of ancestry, the
blood-relationship of organisms, the theory of
descent. Similarly the facts revealed by the study of
paleontology are explicable wholly satisfactorily by the
theory of descent and in no single definitive instance do they
contradict it. Finally, the facts and conditions relating to
the embryology or ontogeny of animals and plants are
similarly wholly in consonance with the theory of descent,
although the brilliant positive evidence for the theory which

18 DARWINISM TO-DAY..

the first revealing of the phenomena of ontogeny led bi-
ologists to expect and even to anticipate has confessedly not
been forthcoming in that overwhelming measure hoped for.
The evidence is excellent and positive and there is much of
it, but the proof that man is descended from a fish because
he has gill-slits at one period in his individual development
is not of the sort to rely on too confidently. The recapitula-
tion theory of Fritz Muller and Haeckel is chiefly con-
spicuous now as a skeleton on which to hang innumerable
exceptions. But the scientific evidence for descent which
embryology offers is neither weak nor slight; it is only less
overwhelming and all-sufficient than its too sanguine early
friends and sponsors attributed to it.

The specific character of the evidence for the theory of
descent derived from the three chief sources just mentioned
cannot claim our attention here. Knowledge of it is cer-
tainly the attribute of all educated readers. If any one
should desire to refresh his memory of it, he may readily do
this by reading his Darwin, or Wallace, or Huxley, Haeckel,
Spencer, Weismann, Romanes, Marshall, Cope,’ et al.
What may for the moment detain us, however, is a reference
to the curiously nearly completely subjective character of
the evidence for both the theory of descent and natural
selection. Biology has been until now a science of observa-
tion ; it is beginning to be one of observation plus experiment.
The evidence for its principal theories might be expected to
be thoroughly objective in character; to be of the nature of
positive, observed, and perhaps experimentally proved, facts.
How is it actually? Speaking by and large we only tell
the general truth when we declare that no indubitable cases
of species-forming or transforming, that is, of descent, have
been observed ; and that no recognised case of natural selec-
tion really selecting has been observed. I hasten to repeat
the names of the Ancon sheep, the Paraguay cattle, the
Porto Santo rabbit, the Artemias of Schmankewitch, and

_ “=
“7
=

DARWINISM AND EVOLUTION DEFINED. 1g

the de Vriesian evening primroses to show that I know my

list of classic possible exceptions to this denial of observed

species-forming, and to refer’ to Weldon’s broad-and
narrow-fronted crabs as a case of what may be an observa-
tion of selection at work. But such a list, even if it could
be extended to a score, or to a hundred, of cases, is ludicrous:
as objective proof of that descent and selection, under
whose domination the forming of millions of species is sup-
posed to have occurred. The evidence for descent is _of
satisfying but purely logical character; the descent hypoth-

esis explains completely all the Prencmers of homology, of

paleontological succession, of ontogeny, and of geographi-
cal distribution; that is, it explains all the observed facts.
touching the appearance in time and place on this earth of
organisms and the facts of their likenesses and unlikenesses
to each other, and this no other theory does. The evidence
for the selection theory we shall refer to in detail in the suc-
ceeding chapters, so we may merely recall now that it also
chiefly rests on the logical conclusion that under the

‘observed fact of over-production, struggle is bound to

- occur; that under the observed fact of miscellaneous varia-

tion, those individuals most fortunate in their variations will
win in the struggle; and, finally, that under the observed
fact of heredity, the winners will transmit to their posterity
their advantageous variations, all of which inter-acting facts
and logically derived processes will be repeated over and
over again, with the result of slow but constant modification
of organic types, that is, formation of new species. In the
light of this subjective character of the evidence for descent
and selection, it is with unusual interest that one notes the
swift development of experimental and statistical investiga-
tion in biology. Experiment and statistics are capable of
mathematical treatment; biology may become an exact
science instead of one solely of observation and induction.

As with the conclusion of this chapter we are practically

ail

mae

20 DARWINISM TO-DAY.

to conclude all reference to the theory of descent, which is
to-day more than ever before an integral and unquestioned
part of biological science, and to devote most of the rest of
our discussion to the theory of natural selection, which
is to-day being subjected to more searching scientific criticism
than ever before since its proposal by Darwin, it will be well
to distinguish, if we can, in the general influence that post-
Darwinian biology has had on associated sciences and
disciplines, that particular influence which each of these two
great theories has had. So that if our faith in either is to
be shaken we may recognise what effects on our sociologic,
pedagogic, and philosophic beliefs this particular weakening
of the biologic basis may have.
The relation of theology * to biology is concerned almost
wholly with the theory of descent. The slow and gradual
forming of species including the particular one,
Relation of | man, and their genetic relationship, the allying
ns a ine of man by blood with the lower animals—these
philosophy, are the two biological conceptions (both in-
cluded in the descent theory) which have been
the chief points of attrition in the coming together of
theology and biology. Darwinism specifically as such, that
is, the selection principle, has had some special attention from
theologians because of its substitution of a causo-mechanical
for a teleological explanation of species-forming, and because
it differs in its interpretation of the time necessary for peopling
the globe with a variety of organic forms from the inter-
pretation, or rather explicitly specific statement, of the first
chapter of Genesis. But on the whole the Darwinian selec-
tion theories could be utterly done away with without making
any appreciable change in the existing relation between
theology and biology. Huxley said this to the theologian
Darwinophobes many years ago.
And practically so with philosophy.’ It is the trans-
formation principle, the principle of continuity, of monism

DARWINISM AND EVOLUTION DEFINED.‘ 21!

in Nature that Evolution represents, that philosophy is con-
cerned to consider. Not the actual how of the modification
and transformism of animal and plant life.
In pedagogy it is also the theory of descent rather
than the selection theory which has been drawn on for
some rather remarkable developments in child-
Relation of — study and instruction. Unfortunately it is ex-
theory of descent
topedagogy. actly on that weakest of the three foundation
pillars of descent, namely, the science of em-
bryology with its Millerian-Haeckelian recapitulation theory
or biogenetic law, that the child-study pedagogues have
builded. The species recapitulates in the ontogeny (develop-
ment) of each of its individuals the course or history of its
phylogeny (descent or evolution). Hence the child corre-
sponds in different periods of its development to the phyletic
stages in the descent of man. As the child is fortunately
well by its fish, dog, and monkey stages before it comes into
the care of the pedagogue, he has to concern himself only
with its safe progress through the various stages of pre-
historic and barbarous man. Detect the precise phyletic
stage, cave-man, stone-age man, hunter and roamer, pastoral
man, agriculturalist, and treat with the little barbarian ac-
cordingly! What simplicity! Only one trouble here for
the pedagogue; the recapitulation theory is mostly wrong;
and what is right in it is mostly so covered up by the
wrong part, that few biologists longer have any confidence
in discovering the right. What then of our generalising
friends, the pedagogues ?
Finally in sociology,” more particularly biological soci-
ology. Here again, to my eyes, much biological sociology
rests on two very insecure bases: (1) a too
Beer deacelt slight acquaintance with biology on the part
tosociology. Of the biological sociologist, and; (2) an
acceptance of, and confidence in, certain biologi-
cal theories which are certainly unwarranted, and are not

22 DARWINISM TO-DAY.

at all shared by the biologists themselves. Biological science
contains much that is proved and certain; but also much
that is nothing more than working hypothesis, provisional
theory, and anticipatory generalisation. As the proved part
is largely of the nature of facts of observation, isolated and
unrelated, and the unproved part is composed of the large
and sweeping generalisations, the plausible, provisional ex-
planations, such as the various theories of heredity, of the
results of struggle, of the development of mutual aid, etc.,
that is, is exactly the sort of material that the sociologist
needs to weave into his biological foundations for the
sociologic study of man, it is exactly this unproved part of
biology that the searching sociologist carries home with him
from his excursions into the biological field. The recapitula-
tion theory looms up large and familiar in biological soci-
ology; it is mostly discredited in biology. The inheritance
of acquired characters serves as basis for much sociology ;
most biologists believe it impossible. The selection theories
are gospel to some sociologists; they are the principal moot
points in present-day biology. And so on. Biology is not
yet come to that stage in its development where it can offer
many solidly founded generalisations on which other sciences
can build. The theory of descent is one such safe great
generalisation; but perhaps Darwinism is not another. At
least many scholars do not believe that it is.

APPENDIX.

* For the insects alone entomologists have estimated, on a basis
of the numbers of new species being annually found and described,
and on the basis of the degree to which the entomological explora-
tion of the earth has been carried, that over two million species
must be in present existence.

* See H. F. Osborn’s “From the Greeks to Darwin” (1895) for a
careful history of the unfolding of the descent idea;
see also Edgar Dacqué. “Der Descendenzgedanke und
seine Geschichte,” 1903; also Carus, J. V., “Geschichte
der Zoologie bis auf J. Miller und C. Darwin,” 1872; also Clodd,

History of de-
scent theory.

DARWINISM AND EVOLUTION DEFINED. 23

Edw., “Pioneers of Evolution from Thales to Huxley,” 1897;
and Quatrefages, A. de, “Les Emules de Darwin,” 2 vols., 1894.

* Many of the hermit crabs (Paguride) which live in the dis-
carded shells of gasteropod molluscs have some species of small
colonial polyp, as Podocoryne, attached to and partly covering the
shell. The polyp colony profits by being carried about and by obtain-
ing bits of food when the crab has succeeded in catching prey and
is tearing it to pieces with his claws, while the crab profits by the
protection afforded it by the stinging threads and nettle cells of
the polyp. Esig saw in the aquaria of the zoological station at
Naples a small octopus which was trying to insert one of its ten-
tacles into a shell to get the crab, quickly driven away by the many
stinging threads with which it was caressed by the polyp colony
seated on the outer surface of the shell. This symbiotic life between
hermit crab and polyp goes so far with some species that the hermit
crabs never rest until they have a polyp colony seated on their shell.

* Among more recent books stating the essential points in this
evidence may be mentioned Conn’s “Evolution of To-day,” 1889;

Books giving Wallace’s “Darwinism,” 1891; A. M. Marshall’s
the evidences for “Lectures on the Darwinian Theory,” 1894; Ro-
descent. manes’s “Darwin and After Darwin,” Vol. I, 1896;
Klaatsch’s “Grundziige der Lehre Darwins,” 1900; Metcalf’s “Out-
line of the Theory of Organic Evolution,” 1904; Weismann’s
“Vortrage tiber Descendenztheorie,” 2 vols., 1902; Eng. trans. 2
vols., 1904; Lotsy, J. P., “Vorlesungen iitber Descendenztheorien,
mit besonderer Beriicksichtigung der botanischen Seite der Frage,”
2 vols., Vol. I, 1906; Jordan and Kellogg, “Evolution and Animal
Life.” 1907.

> For an interesting discussion from the modern point of view of
the relation between Darwinian biology and theology see Haeckel,

Discrcatansot Ernst, “Der Monismus als Band zwischen Religion

polation ofae- und. Wissenschatt,” 18935 also Vetter, Benjamin,
scentandthe- “Die moderne Weltanschauung und der Mensch,”
ology. 1903; also Wasmann, Erich, “Die moderne Biologie

und die Entwicklungstheorie,” 1904. (Author is a Jesuit priest whose
remarkable studies on ants and their messmates have made him well
known to biologists. He accepts the theory of descent, with the ex-
clusion of man from the evolution series.) See also Hutton, F. W.,
“The Lesson of Evolution,” 1902. In this book the author takes a
strong stand for dualism, making the point that the theory of evo-
lution has rescued philosophy from a rigidly monistic materialistic
basis (a mind-in-all-matter theory), and has made necessary a dual-
istic theory (mind-and-matter theory) because of the necessity of
postulating the beginning of life and a beginning of mind. The

goannas DARN A AAP AY ce

pn Seen

24 DARWINISM TO-DAY.

theory of evolution rescues religion from Pantheism, and puts it on a
Theistic basis. ‘It is true, as Pantheists urge, that their only experi-
ence of mind is in connection with matter, but so far as we know
mind is connected only with one kind of matter called protoplasm,
which cannot possibly exist throughout the universe. Consequently
mind must either be absent in large portions of matter or it must
be associated with that matter in some way which quite transcends
their experience. So that we have no more experience of mind
universally distributed through matter than we have of mind dis-
tinct from matter. And the argument for Pantheism breaks down.”
See also Le Conte, Jos., “Evolution, its Nature, its Evidences and
its Relation to Religious Thought,” 1801.
* Of course many books and papers concerning the relation of
biology to philosophy have been written. A good introduction to
Discussions of the subject is Eugen Dreher’s ‘‘Der Darwinismus und
relation of biol- seine Stellung in der Philosophie,” 1877; see also Ver-
ogy and philoso- worn, Max, ‘““Naturwissenschaft und Weltanschauung,”
phy, 1904; also Adickes, Erich, ‘‘Kant contra Haeckel,”
1901; also Emil du Bois-Reymond’s “Uber die Grenzen des Naturer-
kennens,” and “Die Sieben Weltrathsel”’; also Haeckel’s ‘‘Die Welt-
rathsel” (trans. in English as “The Riddle of the Universe’) ; see
also Schurman, J. G., “The Ethical Import of Darwinism,” 1888;
also Huxley, “Evolution and Ethics and Other Essays,” 1894; see
also Reinke, J., “‘Einleitung in die Theoretische Biologie,’ Igot.
The author sets out in this book the philosophic notions of Hart-
mann, Lotze, Wundt, Muller and others concerning the principles
and laws of biology, and does this definitely enough to make his
book a pretty good compend of philosophico-biology.
"See* Herbert Spencer’s “Principles of Sociology”; also Lester
Ward’s “Biological Sociology”; also Benjamin Kidd’s “Social Evo-
lution”; also Curt Michaelis, “‘Prinzipien der natur-
Biology and 4 : : ‘ P
sociology. lichen und sozialen Entwicklungsgeschichte des Men-_
schen,” 1904; also ‘“‘Darwinismus und Sozialwissen-
schaft,’ 1903; see also Schallmeyer, W., ‘“Vererbung und Auslese
in Lebenslauf der Volker,’ 1903.

* The books and papers referred to in notes 5, 6, and 7 are simply
certain ones that have particularly interested the author. The lists
of references make not the slightest pretence to guide the general
reader interested in these special subjects.

CHAPTER 11.
DARWINISM ATTACKED.

ATTACKs on Darwinism have been made, of course, ever
since there was any Darwinism to attack. In those first days
(and months and years) after the “Origin of
Species” was published there were the liveliest
of times for Darwin and his supporters; or
rather chiefly for the supporters. Darwin wisely kept
aloof from the debates. But for the first band of followers
with the indefatigable, the brilliant, and wholly competent
Huxley at its head, there was no lack of opportunities for
jousting. The issue was never doubtful; Huxley and his
informed and equipped scientific companions against the
scientifically ignorant, angry, incautious, and dogmatic
Bishop Wilberforces had unfair odds. The victory came
swiftly and brilliantly to the Darwinians. At this time there
was little distinction made between Darwinism and Evolu-
tion. It was really a battle by the theologians against the
theory of descent. And the theory of descent was, and is,
invulnerable.

Since those warring days of the ’60’s the theory of
descent has been assailed no more, that is in any important

or even interesting way. And the true Darwin-

Picnic ism, the selection doctrine, has also been sub-

of Darwinism. ject to no conspicuous and popularly recognised

attack. The educated public accepted the re-

sults of the first battle as final, and it quietly began to

rearrange its thought and to some degree its actual ways
25

Early attacks
on Darwinism.

26 DARWINISM TO-DAY.

of living in accordance with these newly discovered condi-
tions of life. Nevertheless there has been from the day
of the close of the great first battle to the present moment a
steady and cumulating stream of scientific criticism * of the
Darwinian selection theories. In the last few years, it has,
as already mentioned in the preface and introductory chapter
of this book, reached such proportions, such strength and
extent, as to begin to make itself apparent outside of strictly
biological and naturo-philosophical circles. * Such older
biologists and natural philosophers as von Baer, von Kolli-
ker, Virchow, Nageli, Wigand, and Hartmann, and such
others writing in the nineties and in the present century as
von Sachs, Eimer, Delage, Haacke, Kassowitz, Cope,
Haberlandt, Henslow, Goette, Wolff, Driesch, Packard,
Morgan, Jaeckel, Steinmann, Korschinsky, and de Vries,
are examples which show the distinctly ponderable char-
acter of the anti-Darwinian ranks. Perhaps these names
mean little to the general reader; let me translate them into
the professors of zoology, of botany, of paleontology, and
of pathology, in the universities of Berlin, Paris, Vienna,
Strassburg, Tubingen, Amsterdam, Columbia University,
etc., Now without knowing the man personally, or even
through his particular work, the general reader can safely
attribute to men of such position a certain amount of
scientific training, of proved capacity, and of special ac-
quaintanceship with the subject of their discussion. One
does not come to be a professor of biology in Berlin or
Paris or Columbia solely by caprice of ministers of educa-
tion or boards of trustees; one has proved one’s competency
for the place. To working biologists the names—I have
given, of course, only a selection, and one particularly made
to show variety of interest (botany, zoology, palzontology,
pathology )—mean even more than the positions. They are
mostly associated with recognised scientific attainment and
general intellectual capacity.

DARWINISM ATTACKED. 27

Among the critics of the selection theories we must note
two groups, differing in the character of their criticism
r more in degree than in kind, perhaps, but still
wo groups of — : : ; :
scientificat- importantly differing. One group denies in

tackers, ; ; :
toto any effectiveness or capacity for species-
forming on the part of natural selection, while the other
group, a larger one, sees in natural selection an effective
factor in directing or controlling the general course of

es ——

descent, holding it to adaptive lines, but denies it outright |

any such Allmacht of species control as the more eager
selectionists, the so-called neo-Darwinians or Weismann-
ians, credit it with. This larger group of critics sees in
natural selection an evolutionary factor capable of initiating
nothing, dependent wholly for any effectiveness on some
primary factor or factors controlling the origin and direc-
tion of variation, but wholly capable of extinguishing all
unadapted, unfit lines of development, and, in this way, of
exercising decisive final control over the general course of
descent, 7. €., organic evolution. Another classification of
critics may be made on the basis of pure destructiveness on
the one hand as opposed to destructiveness combined with
constructiveness on the other. That is, some critics of selec-
tion, as Wolff, Pfeffer, Driesch, e¢ al., are content with doing
their best to reveal the incapacity of Darwinism; others,
on the contrary, come with certain more or less well-outlined
substitutionary theories in their hands. Eimer with his
theory of orthogenesis, and Korschinsky and de Vries with
their theory of mutations, are examples of the latter class.
The general impression left on one after a considerable
course of anti-Darwinian reading ranging all the way from
the extreme attitude and the violence of Den-

Pigs de Be nert, Fleischmann, Wolff, and Coe, to the
ee substitu- tempered and reserved criticism of Delage and
de Vries, is that there is a very real and effective

amount of destructive criticism for Darwinians to meet; and

28 DARWINISM TO-DAY.

at the same time a curious paucity of satisfactory or at all
convincing substitutionary theory offered by the anti-
Darwinians to replace that which they are attempting to
dethrone. The situation illustrates-admirably the varying
worth of a few facts. A few stubborn facts of the wrong
complexion are fatal things for a theory ; they are immensely
effective offensive weapons. But these same few facts make
__-a pitiable showing when they are called on to support a
theory of their own. It was exactly the greatest part of
Darwin's greatness, it seems to me, that he launched his.
theory only after making the most remarkable collection of
facts yet gathered together in biological science by any one
man. Testing his theory by applying to it successively
fact after fact, group after group and category after category
of facts, he convinced himself of the theory’s consonance
with all this vast array of observed biological actuality.
Compare the grounding of any of the now offered replacing
theories with the preparation and founding of Darwinism.
In 1864 von Kolliker,” a great biologist, convinced of the
incapacity of natural selection to do the work assigned it by
its founders and friends, suggested a theory of the origin of
species by considerable leaps ; in 1899, Korschinsky,’ on the
basis of some few personal observations and the compiling
of some others, definitely formulated a theory of species-
forming by sudden considerable variations, namely, muta-
tions; in 1901 and 1903 appeared the two volumes of de
Vries’ s “Die Mutationstheorie,” in which are revealed the
results of long years of careful personal observation, in
truly Darwinian manner, directed toward the testing and
better grounding of this mutationstheorie of species-origin.
The results are: out of many plant species studied, a few
show at certain times in the course of numerous generations
a behaviour in accordance with the demands of a theory
of species-forming by sudden definitive modification; that
is, species-forming by mutations. The mutations-theory

DARWINISM ATTACKED. 29

thus launched is offered as a substitute for the natural

selection theory obviously weakening under the fire of

modern scientific criticism. But however effective de
Vries’s facts are in proving the possibility of the occurrence
of other variations than those fortuitous ones occurring in

continuous series from mean to opposite extremes which Dar-

win recognised as the basis of species-forming, and however
effective they are in proving the actual production of three
or six or ten species by mutation, and however effective in
both these capacities they are as weapons of attack on the
dominance of the Darwinian theory of species-making,
how really inadequate are they to serve as the basis of a .
great all-answering theory explaining, in a causo-mechanical
way, the facts of descent, or even the primary facts of gen-
eral species-forming. And yet the first American book *
(from the pen of one of America’s foremost biologists) to
discuss the modern phase of unrest and dissatisfaction in
evolutionary matters, practically accepts the mutations-
theory as a substitute for the selection theory of species-
forming. It cannot be, it seems to me, that Professor
Morgan is so satisfied with the mutations-theory, that he
clutches it up, hardly definitely formed and cooled, from the

de Vriesian moulds, but that he is, like many another present-

day biologist, so profoundly dissatisfied with the natural
selection theory. For my part it seems better to go back
to the old and safe Jgnoramus ° standpoint.

But I have been led to anticipate my conclusions; let us
make another beginning with the real undertaking of this
chapter and get to the actual specifications of “Darwinism
Attacked.” We shall concentrate the attacks and attackers in
this and the two following chapters ; then include in the suc-
ceeding two the defence and the defenders, and in the next
four chapters the various supporting and substitutionary
theories offered by the friends and foes of Darwinism.
Finally, in the last chapter we shall set out what we can

30 DARWINISM TO-DAY.

discover, in the haze of the smoke of battle, of the actual
present state of the besieged and besiegers.

Distinctly the most comprehensive, the fairest-minded
review of gegen-und-fiir Darwinismus in recent literature is
Plate’s extension of his address, “Uber die Bedeutung des
Darwin’schen Selectionsprincips,’ made in Hamburg be-
fore the Deutsche Zoologische Gesellschaft in 1899. To
this review, as published in 1903 after being extended and
brought up to date, I beg to acknowledge a special indebted-
ness in my present attempt to get together the more im-
portant criticism, both adverse and defensive, of Darwin.
I have, however, assiduously sought out (with the help of
librarians and my indefatigable Leipzig book-dealer friend
Bernh. Liebisch), and perused the original pourings-forth of
criticism and vilification even to the reading of some matter
written by certain Roman Catholic priests with a consider-
able amateur interest in natural history and a strong pro-
fessional interest in anti-Darwinism! But Plate has been
a guiding hand in this search for active attacks and de-
fence.

The natural selection theory as an all-sufficient explanation

ness at its base; it depends absolutely, of course,
Natural selec- on the pre-existence of variations, but it itself
tion theory based : Aas
on variation. | has no influence whatever on the origin or con-

trol of these variations except in so far as it may
determine what individuals shall be permitted to give birth
to other individuals. Now one of the chief problems in
biology is exactly that of the origin, the causes, and the
primary control of these congenital variations.* Three
principal explanations, no one of them experimentally
proved or even fairly tested as yet, have been given of this
actually occurring congenital variation, viz., (1) that there
exists in the germ-plasm an inherent tendency or capacity
to vary so that there is inevitable variation in all individuals

DARWINISM ATTACKED. 35

produced from germ-plasm, this variation being wholly
fortuitous and fluctuating according to some (the belief of
Darwin and his followers), or, according to others, this
variation following certain fixed or determinate lines (de-
terminate variation, orthogenetic variation, etc.) ; (2)) that
amphimixis, 1. e., bi-parental parentage, is the principal
cause of variation, it seeming logical to presume that indi-
viduals produced from germ-cells derived from the fusion
of germ-plasm coming from two individuals more or less
unlike would differ ‘slightly from either of the parental
individuals ; and (3), that congenital variation is due to the
influence of the ever- -varying environment of the germ-cell
producing individuals. The objections to any one of these
theories may be very pertinent, as when one says regarding
the first that calling a thing “inherent” is not clearing up in
any degree a phenomenon for which we are demanding a
causo-mechanical explanation; or of the second that it has
been proved * that individuals produced parthenogenetically,
that is, from an unmated mother, vary and in some cases
vary even more than do other individuals of the same species
produced by amphimixis; or of the third that as far as our
study of the actual processes and mechanism of the produc-
tion of germ-cells and of embryos has gone, we have found
no apparent means whereby this influence of the ambient
medium can be successfully impressed on the germ-plasm.
But however pertinent the objections to the why of varia-
tion may be they do not in any way invalidate the fact that
variations do continuously and inevitably occur in all indi-
viduals, and that while many of these variations are recog-
nisably such as have been impressed on the individual during
its personal development as immediate results of varying
temperature, amount or kind of food, degree of humidity,
etc., to which it may be exposed in its young life, others
seem wholly inexplicable on a basis of varying individual
environment and are certainly due to some antenatal influ-

ee DARWINISM TO-DAY.

ence acting on the germ-plasm from which the embryo is
derived.
Now the natural selection theory, in its Darwinian and
neo-Darwinian form, presupposes fortuitously occurring
congenital variations of practically infinite
ee ee in all parts of all organisms. Actual
tion according to) Observation shows that all parts of all organ-
neat ” isms do vary and that they vary congenitally,
that is, independently of any immediate in-
fluence during development exercised from without by
environmental conditions, as well as in response to these
environmental influences, and finally that in many cases this
variation is fortuitous, that is, that it occurs according to
the laws * of chance. The industrious statistical study of
variations, including the tabulation of the variation con-
dition in long series of individuals of the same species or
race and the mathematical formulation of this variation
condition, have shown that in many specific cases, studied
in numerous kinds of animal and plant forms, the character
of the variation in any particular character may be truly
represented (with close approximation) by the mathematical
expression and curve which would exactly define the condi-
tion in which the variation would exist if it actually followed
the law of error. It is these continuous series of slight
variations, these variously called fluctuating, individual, or
Darwinian variations, occurring in all organisms at all times
and often following, in their occurrence, the laws of chance,
on which Darwin’s theory of species-forming by natural
selection is based. But this same industrious statistical
and quantitative study of variation, which has proved
that some variations do occur regularly, fluctuating
around a mean or mode, has shown, as well, that in
many cases the variations distinctly tend to heap up
on one side or the other of the mean, that is, that they
tend to occur along certain lines or toward certain direc-

DARWINISM ATTACKED. 33

tions rather than uniformly out in all directions. Also it
is true, and this has of course been long known, that by
no means all variations are so slight nor in
such perfectly gradatory or continuous series
as is true of the gradatory Darwinian variations.
“Sports” have been known to breeders of plants and animals
ever since plant and animal breeding began. Bateson has
filled a large book’ with records of “discontinuous varia-
tions” in animals; variations, that is, of large size and not
occurring as members of continuous gradatory series. So
that biologists are acquainted with many cases of variation
that seem to be of a kind, or to exhibit a tendency, to in-
stitute special directions of development, and thus not to be
of the simple, non-initiating, inert character of the fortuitous,
slight, fluctuating variations, among which natural selection
is presumed to choose those that are to become the be-
ginnings of new lines of modification and descent. Many
biologists believe firmly that variations occur in many
special cases, if not in most cases, only along certain special
lines. Palzontologists believe, practically as a united body, |
that variation has followed fixed lines through the ages;
that there has been no such unrestricted and utterly free play
of variational vagary as the Darwinian natural selection
theory presupposes.

Now it is at least obvious that natural selection is abso-
lutely limited in its work to the material furnished by varia-
tion; so that if variation occurs in any cases
only along certain determinate lines selection

Discontinuous
‘variation.

Determinate

variation as8@ = =¢can do no more than make use of these lines.

species-forming : Rae ;
factor. Indeed if variation can occur persistently along

determinate lines natural selection’s function in
controlling evolution in such cases is limited to the police
power of restricting or inhibiting further development along
any one or more of these lines which are of a disadvan-
tageous character, that is, a character which handicaps or

34 DARWINISM TO-DAY.

destroys the efficiency of its members in the struggle for life.
The question in many men’s mouths to-day is, Why may not
variation be the actual determinant factor in species-forming,
in descent? It actually is, respond many biologists and
palzontologists.

Even Darwin believed such determinate variation to occur,
as is indicated by repeated statements in the “Origin of
Species.” In chapter iv he says (to refer to but a single
one of these admissions) : “It should not, however, be over-
looked that certain rather strongly marked variations, which
no one would rank as mere individual differences, fre-
quently recur owing to a similar organisation being similarly
acted on—of which fact numerous instances could be given
with our domestic productions. In such cases, if the vary-
ing individual did not actually transmit to its offspring its
newly acquired character, it would undoubtedly transmit to
them, as long as the existing conditions remain the same,
a still stronger tendency to vary in the same manner. There
can also be little doubt that the tendency to vary in the
same manner has often been so strong that all the individuals
of the same species have been similarly modified without the
aid of any form of selection. Or only a third, fifth, or
tenth part of the individuals may have been thus affected, of
which fact several instances could be given. Thus Graba
estimates that about one-fifth of the guillemots in the Faroe
Islands consist of a variety so well marked, that it was
formerly ranked as a distinct species under the name of
Uria lacrymans. In cases of this kind, if the variation were
of a beneficial nature, the original form would soon be sup-
planted by the modified form, through the survival of the
fittest.”

This problem of the existence or non-existence of deter-
minate variation is taken up in such detail in connection with
the explanation and discussion of various auxiliary or alter-
native theories of species-forming in later chapters of this

DARWINISM ATTACKED. 35

book that it need not detain us now. But to my mind it is
one of the most important matters in connection with the

ee whole great problem of descent, that is, of
nate variation €VOlution. It is the basic problem of evolu-
bal tion, for it is the problem of beginnings.
Selection, isolation, and the like factors are conditions
of species-forming; variation is a prerequisite, a sine
qua non. True variation must have its causes, and these
causes are to be determined before an actual causo-me-
chanical explanation of evolution can ever be found. But
the determination of the relation of variation to species-
forming is certainly the first step now necessary in our
search for the basic factors, the real first causes of species
change.

But even in those cases where there may exist unrestricted
indeterminate fluctuating variation in continuous series ac-

Whatdoes COrding to the law of error, what is it that this
fluctuating vati- variation really offers natural selection to
ation offer selec- P
tion asa basisfor WOrK on? Remember what natural selection
species-forming? is : the saving of one or ten by the actual killing
of the thousand or ten thousand because in the struggle for
existence the variations of the one or ten are of sufficient
advantage to have a life-or-death-determining value. Now
between any two successive individuals in a series arranged
on a basis of the variations in any one character of any one
organ or function, the difference is extremely slight, too
slight, one is certain, to be, in most cases, of life or death
value. But even if one’s conception of the absolute inten-
sity of the rigour of the personal struggle leads to a
logical conception of an absolute advantage in any differ-
ence, however slight, in a favourable direction, it is wholly
possible that for any other characteristic equally important
in the struggle the two individuals may be in exactly reversed
position, the one possessing the infinitesimal advantage in
strength say, possessing an infinitesimal disadvantage in

36 DARWINISM TO-DAY.

sharpness of claw or in agility. What of the chances for
such a necessary coincidence in the one individual of favour-
able variations in all the ways necessary to create a real life-
or-death-determining advantage? The law of probabilities
answers that much to the dismay of the Darwinian. But,
again, why not compare the chances in the struggle of two
individuals not standing side by side in a variational series,
but at two extremes of the range; the difference here can be
considerable, can be of positive advantage or disadvantage.
Yes, but again comes the necessity of presupposing a coin-
cidence of other advantages or at least of no coincidence of
balancing advantages and disadvantages. But even more
fatal is the condition that if an extreme variation in some one
character could be of a life-preserving advantage, yet by the
law of probabilities (and by the tale of actual observation)
those individuals standing at the extremes of the range of
variation are very, very few compared with those standing
nearer the mean, or mode, of the series, and there would
be almost a certainty of such an extreme-charactered sur-
vivor not finding a similar form with which to mate and thus
insure perpetuation of the advantage, the mating of the
individuals admittedly not depending on any necessary
similarity in variation (unless the varying characteristics
happen to be actually concerned with the mating act: see
later discussion of biological isolation, chapter ix). Con-
siderable variations, the only ones of apparent worth in a
life-and-death struggle, are in such meagre disproportion
to the less considerable that they are inevitably swamped,
extinguished, in miscellaneous cross-mating.

Let us consider a little more in detail each of the various
objections mentioned in the last few pages. Only the student

asteitheae of systematic (classificatory ) zoology or botany
of fluctuating can realise how slight and insignificant are the
aa various miscellaneous individual variations
which make up that basis of ever-present, myriad-faced,

DARWINISM ATTACKED. 37

fortuitous, fluctuating variability on which the whole great
structure of the selection theory is based. Yet any one’s
common sense and his intuitive comprehension of what
life-and-death value is in an animal’s battle with another,
with foreign enemies, or with inclement Nature, make
this objection of “no handle for natural selection in mis-
cellaneous slight variation” thoroughly appreciable. Polar
bears are probably descended from brown; and their white
fur coat is probably an advantageous adaptation in their
life in the Arctic. But did the fortuitous appearance in his.
coat of a spot of white hairs as large as a dollar or a pancake
give some ancient brown bear such an advantage in the
struggle for existence as to make him or her the fore-
runner of a new and better-adapted sort of bear? The
giraffe’s long neck is very much worth while to it; it gets.
leaves from the higher branches unattainable by the short-
necked animals who find food in the same range. But did a
millimetre or even an inch of extra neck appearing as
individual variation in an ancestral short-necked giraffe
kind give natural selection a handle with which to grind out
a new species? The consideration of the usefulness of
slight variations too often leads to an argument for their
usefulness on the same grounds as sustain the belief that
the hound will never catch the hare which goes one-half as
fast as the dog. For each time the hound covers the given
stretch that lies between him and the hare at any given
moment the hare will be just one-half that distance in
advance—and though the distance will get ever shorter and
shorter the hare will ever be one-half the last distance ahead.
So say the sophists. As a matter of fact the hound gets the
hare.

Spencer’s example of the femur of the whale is a striking
illustration of the reality of the absurdity connected with
the argument of change on a basis of the selection of in-
finitesimal differences. The femur of the whale, says

38 DARWINISM TO-DAY.

Spencer, is evidently the atrophied rudiment of a bone once
much larger. It weighs now about one ounce, less than a
Bani: millionth of the weight of the whote body.
ample of the Let us suppose that when it weighed two
ca aa ounces an individual had a femur which by
variational chance weighed but one ounce.
What advantage over other whales would the difference give
it? What fraction of the daily nourishment would this ad-
vantageous variation permit the fortunate whale to add to its
stored fat instead of spending it on an extra ounce of useless
femur? Who would dare claim that this variation would
aid in success in the struggle for existence? And yet this is
the argument for the reduction of useless organs through
the influence of natural selection. Roux and Weismann,
realising the absurdity of the argument, have put forward
two theories, one called the ‘battle of the parts” and the
other the “theory of germinal selection” to aid the selection
theory to explain the degeneration and reduction of organs.
The reader will find these theories explained in chapter viii.
Every student of systematic zoology or botany has a keen
realisation, too, of the fact that a majority of the distinguish-
ing characters which he recognises in the vari-
Many species Ous species and genera that come under his
characters of no P
utility, eye are of a sort that reveal to him no trace of
particular utility or advantage. Indeed he can
go farther and express, to himself at least, his conviction
that many of these slight but constant specific differences *°
can actually have no special advantageousness about them.
One’s experience as an observer of nature and one’s common
sense combine to protest against that easy and sweeping
answer of the Darwinians: “shall “poor blind man’ say what
characteristic, however slight and insignificant, is or is not
of advantage in the great complex of nature?’ As the
whole question after all resolves itself into one for which
“poor blind man” is attempting to find an answer satisfying

DARWINISM ATTACKED. 39

to his own understanding, however short of perfection and —
omniscience that is, he is bound to answer the subsidiary
-problems such as usefulness or non-usefulness on a basis of
his own seeing and understanding capacity. As a matter
of fact the indifference of many specific characteristics of
organisms is not denied by selectionists. Romanes ** was
perhaps the first representative Darwinian, after Darwin
himself, to admit this. But many biologists say, further, on
a basis of their experience as observers, that these very
indifferent, meaningless (as far as utility goes) mor-
phological characteristics and differences are much more
constant in their character than the obviously adaptive, 7. ¢.,
useful ones. However, as pointed out first by Nageli, accord-
ing to the selection theory the characteristics of organisms
should be just in that degree the more constant, the more
useful they are. Hence there is here a serious discrepancy
between theory and fact. Darwin himself felt the force of
this objection and met it in a manner not at all acceptable
to the ultra-Darwinians, that is the strict selectionists of
post-Darwinian times. He admitted that these trivial, ap-
parently non-useful, but constant specific characters could
not be explained by natural selection, and must be due to a
fixation in the species of these characters at one time or
another through the nature of the organism and the influ-
ence of extrinsic influences; a true Lamarckian or at least
anti-Weismannian * explanation.

This objection to the selection theory based on the ad-

* Students and readers who have not read Darwin recently, or
in the light of the controversy between the neo-Darwinians and the
neo-Lamarckians, that is, between those who disbelieve and those
who believe in the inheritance of acquired characters, will be sur-
prised to note on a careful re-reading of the “Origin of Species,”
with this post-Darwinian sharp distinction in mind, how often Dar-
win calls on the Lamarckian factors to help his species-forming
theories out of tight places. Morgan in his “Evolution and Adap-
tation” points out many cases of this.

40 DARWINISM TO-DAY.

mitted existence of indifferent species characters is well stated

phe Oe “as follows: “But how is it with char-
ment of theob- acters that have no utility? It is, of course, a
er great achievement to be able to point out the
trivial charace method by which adaptations have been pro-
i duced, but if animals have some characters that
are not useful, natural selection does not explain them.
Natural selection can develop useful organs only. The real
problem which our naturalists are trying to solve is not the
origin of adaptations simply but the origin of species also.
Now while many of the characters and organs of animals.
and plants are of utility to the individual there are others
that appear to be useless. As animals and plants are
studied, it is found that the different species differ from
each other by certain definite characters. These distinctive
peculiarities that distinguish species are called ‘specific
characters, and this term will be hereafter used in this
sense. The explanation of the origin of species must then
account for the origin of specific characters. Now specific
characters are frequently trivial in nature. This was long
ago recognised by Darwin, who saw that the characters by
which species are distinguished are frequently so trivial as to
be apparently useless. If, however, we are to explain the
origin of species we must find an explanation of these trivial
characters as well as the more important ones. If these
trivial characters are of no use to their possessors, then
manifestly the principle of the survival of the fittest does.
not account for them. The fact that species are so com-
monly separated by characters that seem to be absolutely
useless has led some of our keenest naturalists to insist that
the survival of the fittest does not explain the origin of
species, but explains only the origin of adaptations. At all
events, it is clear that the problem of the utility of specific
characters is a very fundamental one to the discussion of the
principle of survival.

DARWINISM ATTACKED. ai

“We here come to the first parting of the ways between
scientists of different schools. On the one hand we find those
who are so thoroughly convinced of the universality of the
principle of natural selection that they insist that all specific
characters are useful, however useless they may seem. It
is beyond question that they are led to this belief in the
utility of all characters, not from observation, but simply
from their belief in the sufficiency of the law of natural
selection. They tell us that we know too little of the actual
life of organisms in nature to enable us to say that any
given character is not of use; and to make a claim that any-
thing, no matter how trivial, is useless, is simply to confess
ignorance. We must acknowledge that many seemingly
useless organs have been found to have utility as soon as the
life habits of animals are better understood. Certainly,
utility has been found more universal than was believed to
be possible a quarter of a century ago. The followers of
Darwin have given very much attention to this matter.
They have pointed out many lines of utility hitherto not
dreamed of. They have considered great multitudes of
cases of seemingly useless characters, and by a little imagina-
tion have suggested some use to which they may be adapted.
If one reads the recent works of Wallace, the most promi-
nent advocate of this position, he will not fail to be im-
pressed with the fact that utility is much more widely
applicable as an explanation of seemingly trivial characters
than might have been thought possible. The position held
by this writer is, that inasmuch as the law of natural
selection is a universal force which all admit, while all other
forces of evolution are yet in dispute, and inasmuch as many
seemingly useless organs have been shown to be of use, it is
perfectly legitimate to claim that when we come to under-
stand them, we shall find that all characters are of value, and
that the principle of survival of the fittest has been concerned
in the development of them all. If this is true, the survival

42 DARWINISM TO-DAY.

of the fittest explains the origin of species as well as the
origin of adaptations, since all specific characters are really
adaptations.

“But on the other hand, many naturalists think that there
are specific characters for which we cannot only see no
utility, but which are demonstrably of no use. A few illus-
trations will serve to make the matter clearer. Certain in-
sects are distinguished from each other in accordance with
whether they possess one or two bristles on the head. Here
is a character which appears to be constant, and which must
therefore be explained by any complete theory of the origin
of species. Can we imagine that the question of whether
the animal has one or two hairs should ever have been of
selective value? But if developed by natural selection, this
character must at some time have been a matter of life and
death. Again among snails, the shells commonly coil in
the same direction in the same species, this fact making the
direction of the coiling of the shell a specific character. But
clearly this is not a matter of selective value, since living
among the rest of the individuals will frequently be found
some with their shells coiled in the opposite direction.
Again, horses have small horny callosities on their feet. No
one has suggested any possible use for them, but neverthe-
less they are present on the feet of all the species of the horse
family. But the most curious fact is that while the horse has
them on all four feet, the ass has them on only two. Now,
upon the principle that utility is universal, it would be neces-
sary to claim, not only that the presence of four callosities
has been a matter of selective value in the horse, an ex-
tremely difficult thing to believe, but also that the presence
of only two instead of four has been of selective value in the
ass. This position approaches absurdity. Again, there are
molluscs characterised by special markings of the shell,
which markings are constant enough to be specific char-
acters, and must, of course, be included in any explanation

DARWINISM ATTACKED. 43

of the origin of species. But these marks are demonstrably
of no use, since they are entirely covered by the epidermis |
of the animal when alive, and absoiutely invisible. Again,
some birds have slight differences in colour markings which
separate species. Now these differences may perhaps be re-
garded as of use as protective or as recognition marks.
But in some cases the colour markings are entirely con-
cealed by other feathers and, being invisible, can be of no
possible utility. It is hardly possible for one, unless he has
decided previously to accept the all-sufficiency of natural
selection, to believe that there can be any utility in the very
slight differences in the shape of leaves of plants, in the micro-
scopic markings of the hairs of different species of mammals,
the exact numbers of the feathers in the tails of birds, the
peculiar distribution of the veins in the wings of a butter-
fly, the microscopic markings in the scales on its wings, or
a host of other similar trivial characters. When it is re-
membered that the selection principle would force us to
insist that all of these characters are of value sufficient to
protect their possessors at the expense of other individuals
not possessing them, it is evident that the burden thrown
upon the principle of survival becomes very great. When
finally we come to characters of specific nature connected
with colour markings which are invisible when the animal
is alive, there is apparently no resource left except to con-
clude that the principle of survival because of utility does
not account for everything.”

It is indeed the general recognition by naturalists of the
fact of the triviality or indifference of a majority of specific
characters that has led to the recent renewal of the import-
ance of isolation theories, particularly of geographical
isolation. The rehabilitation of Moritz Wagner’s theory of
species-forming by migration and isolation is a conspicuous
feature in present-day evolution discussion. The way in
‘which isolation comes to the aid of selection, or even sup-

44 DARWINISM TO-DAY.

plants it in the minds of some, in species-forming is pointed
out in chapter ix, to which the interested reader may
FeTer,

But in those cases where the differences or variation
among individuals may be or obviously are of the character

The swamping Of useful ones, and where by comparing ex-
or extinguishing tremes of this variation the life-and-death-
of favourable va-
riations by inter- determining worth of this utility might be
crectine: conceded, still. what chance is there for the
perpetuation of this advantage? Nageli long ago pointed
out that the extreme variations, that is, the rare variations,
would in almost every case be inevitably extinguished by
interbreeding. If a certain considerable variation occurred
in one individual of a hundred born, in 20,000 individuals of
the species 200 would have this worth-while variation.
Now if the chances of mating are the same for all there
would be 9,801 parings of individuals not showing the
variations, 198 pairings between a varying individual and a
non-varying one, and a single mating between two indi-
viduals both preserving the considerable variation. In fact
every rare variation will, as Delage says, be immediately
effaced by the dilution of the blood of the varying individual
by that of the great mass of individuals not possessed of the
particular variation. This inevitable swamping of the ad-
vantageous variations of individuals has long ago led to the
practical giving up by Darwinians of any claims to species-
forming or evolution on the basis of extreme or rare varia-
tions and to the restriction of the selecting influence to
masses. The species must be changed through the selection
of it as a mass or unit rather than through the selection of
special scattered individuals of it.

But for the selection of masses of individuals sufficiently
considerable to avoid the extinguishing of the fortunate
variations by interbreeding, and to insure a repetition of
the advantage and an opportunity for its fostering and

DARWINISM ATTACKED. 45

increase, there is necessary an extraordinary coincidence in
the appearance of the needed variations in many forms at
The needed co- the right time. That is,atheory based on chance
incident occur- or accidental phenomena demands after all the
‘rence of several :
variations atone assumption of the occurrence of phenomena
‘time, of the right kind at the right moment, and
the persistence of such occurrences through a definite
time-period. This is too much to assume, too much to ask
even of those of the true faith, say the antagonists ** ** of
the selection theory. Kronig ** makes sport of the selection
‘doctrine by having his rather frivolous character, Sabtich-
winski, undertake to have made, by a foolish clown, various
trifling changes in all kinds of industrial products with the
expectation of bringing them into the market. He is con-
vinced that he will win a fortune by this, for he says to
himself that the struggle for supremacy must work out the
same in the industries as in nature, and in his case with the
added advantage that the changes effected by even the most
slender-witted boor must result better than those which are
the outcome of perfectly blind chance. Indeed, from the
very heart of the neo-Darwinian ranks come signs of dis-
may when this objection is faced. Weismann, leader of the
ultra-selectionists, practically concedes the irrefutability of
this objection to the Allmacht of selection when he intro-
duces a statement of his latest theory, that of Germinal
Selection, by saying :** “Knowing this factor [that of germi-
nal selection] we remove, it seems to me, the
Weismann’s eps .
admission of the Patent contradiction of the assumption that the
nu paar general fitness of organisms or the adaptations
necessary to their existence are produced by
accidental variations—a contradiction which formed a seri-
ous stumbling-block to the theory of selection.” And the
formulation of the theory of germinal selection is of itself
a practical confession on the part of the foremost neo-
Darwinian of the inability of natural selection to explain

46 DARWINISM TO-DAY.

species-forming without calling to its aid some effective
factor to control in its beginnings the variation essential
as the basis of the selective action.

Pfeffer ** and Wolff ** have been particularly keen and
severe in their criticism of the selection theory on the basis
of this objection. And Morgan” in this country has also
made effective use of this weapon in his destructive con-
sideration of the Darwinian theories.

There is an additional point about this difficulty of the
necessity for a certain regularity or reliability of variation

etinein tee in order to make a beginning basis for the action
coincident ap- of selection. It is this. Close scrutiny reveals
pearance of other the necessity often of the occurrence of several

variations to
make acertain coincident variations in order to make any one

one effective, characteristic positively advantageous. What
advantage in the way of increased speed is a slight added
length of leg without a simultaneously added strength of
musculation; or an increase in size of antlers without a
simultaneous increase in strength of neck muscles to sup-
port and manipulate the heavier head? What faint prob-
ability of the occurrence coincidently of the necessary varia-
tions (if determined only by chance, that is, the law of prob-
ability) to produce a gradual perfecting of so complex
a structure as the vertebrate eye? Or, more, how incon-
ceivable the coincidences, if variation is purely fortuitous,
necessary to the simultaneous development of two exactly
similar eyes: two eyes so intimately associated physio-
logically that normal sight is a function of both these
separated organs working perfectly together. Is variation
to be assumed to be governed by some law of bilateral
symmetry? But I have shown for many cases *° that in such
perfectly and fundamentally bilaterally symmetrical animals
as insects neither the usual Darwinian fluctuating variation
nor the rarer discontinuous or sport variation is governed
at all by sucha law. In fact the independence of the varia-

DARWINISM ATTACKED. 47

tion phenomena in right and left members of bilaterally
arranged pairs of organs as wings, antenne, legs, etc., is a
noticeable fact. This denial of the capacity of the selection
of fortuitous slight variations to account for coadaptation
and for the continuous perfecting of complex organs has
been stated as follows: “It is highly improbable that for the
steady perfecting of an organ, the variations needed by
selection will always appear just at the right time.” Or in
more expanded form: “It is highly improbable that during
the modification of a complex organ such as a whole body
part, or during the gradual perfecting of an adaptive modi-
fication, the numerous necessary variations will appear suc-
cessively in such series that a harmonious combination of
the single variations will be possible.” The objection cer-
tainly needs no elaboration. The Darwinian variations ap-
pear in all directions at all times in slight degrees with no
determinate direction nor correlation. Selection is to find
in these variations its only material with which to build up
to wonderful complexity and perfection of coadaptation
and correlation of parts ** on a basis of constant advantage,
such an intricate but harmoniously adjusted compound organ
as the human eye, in which the failure or imperfectness of a
single minute part can at any time, during the course of
development, rob the whole of any advantage whatever to
the organism possessing: it.

Wolff ** enlarges on the difficulty of explaining any
identical structures of the animal body which appear in one

Difficulty of and the same organism to the number of two
explaining re- or more. “It cannot be explained,” he says, “by
peated identical P :
structures by Selection, how the carnivores, for example, can
selection. have developed through fortuitous yet always
similar variations, two-such structures agreeing in all de-
tails as the back teeth, which have developed in course of
time from small skin teeth. That a tooth can develop into
such an admirable biting organ through chance variation may

48 DARWINISM TO-DAY.

be explicable by selection, because we are accustomed to
postulate thoroughly fortuitous and all-inclusive variation ;
but that the tooth standing next to it shall have varied al-
ways in exactly the same way so that the result of its de-
velopment shall make it identical with the other one, is
inexplicable by selection on a basis of fortuitous variation,
but rather indicates that the change of form is ruled by law
which we do not know. The attempt to discover it is the
most imperative task for biologists to undertake.”

Wolff * follows this argument farther by discussing other
particular examples, but they are all of the type of the one

Spencer’s pic. JuSt set out. Spencer pictures the situation of
ture ofthe inu- the herbivorous animals in a country of in-
tility of advan- ‘
tageinasingle Clement climate and populated by numerous
eerie carnivores. Now those herbivores which have
the finest hearing will be soonest aware of the approach of
the tiger, but those with keenest sight or most perfect sense
of smell will also perceive, as soon, that it is time to flee. But
what advantage over others will the first start in flight give
them? Others less delicately endowed with sense organs
but swifter of foot will, although starting a little later, have
as good a chance to escape because of their more rapid run-
ning. Later may come snow and terrible cold. Those in-
dividuals best endowed with sense-organs or swiftest of foot
will not necessarily be the most enduring or the best
equipped with instincts to find shelter. The climate may
decimate those which selection on the basis of special senses
or speed has saved. But after the cold may come the sum-
mer drought. Those most heavily furred or warmest-
blooded which have successfully endured the low temperature
and snow and ice of winter should be the first to suffer from
the attacks of sun and drought and lack of food in the
summer. Thus no individual has, because of advantage in
any one character, any real and complete superiority which
guarantees it success in all the phases of the struggle for

DARWINISM ATTACKED, ees

existence: the advantages are scattered and compensated
by disadvantages.** |

In connection with the objection stated in the preceding
paragraphs is that specially pressed by Wolff, although long

Numerous use- 2£0 strongly stated by Mivart,** and one that
Papeete has long appealed strongly to me particularly in
in highly per- COmnection with the study of the utility of
fected staten = colour and pattern among insects. This ob-
jection is, that numerous useful characteristics or adapta-
tions of organisms are useful only in a highly perfected
state, often involving a complex and considerable structural
development of old (then much modified) or quite new parts,
and hence could not have arisen by gradual modification by
the selection of slight variations. Darwin himself says that .
if a single complex organ can be referred to whose full de-
velopment cannot possibly be explained through numerous
small successive modifications, then his theory must indubi-
tably fall. For example, the electric organ of the torpedoes,
the brood-sacks or cells on the back of Pipa dorsigera, the
chameleon’s tongue, and many other organs can be recalled
which could not possibly exercise their particular advanta-
geous function in an undeveloped and beginning state. In
my own eyes has for long stood the familiar case of the
mimicry, of our common American monarch butterfly,

Mimicry of Anosia plexippus, by the viceroy butterfly,
Anosia by Basilarchia archippus. The viceroy belongs to a
epearule group of species in which the prevailing (almost
certainly the ancestral) colour and pattern are white and
black (or iridescent purplish and bluish) arranged as a broad
white continuous transversal bar across both fore and hind
wings, on a black (to purplish) ground. The colour and
pattern of Anosia are radically different; brick-red ground,
black longitudinal lines following the veins and small white
spots in an irregular black submarginal band. Examine the
viceroy butterfly. You find no suggestion of typical Bast-

5° DARWINISM TO-DAY.

larchia type of colour and pattern; on the contrary, you
find an extraordinarily faithful imitation (duplication) of
Anosia’s colour and pattern. Only in a narrow black trans-
versal streak across the outer disc of each hind wing is there
any divergence in the viceroy from the Anosia pattern.
Now Anosia is distasteful to birds; after a few experiments
with Anosia a bird recognising this ill-tasting morsel in its
conspicuous red-brown livery leaves the monarchs alone. Not
only monarchs, however, but also viceroys, which are to all
external seeming only slightly smaller monarchs. The viceroy
is, however, not distasteful; it would be a welcome bonne
bouche to any bird that could distinguish it. But thanks to
its perfectly mimicking colour-pattern it wings its deceitful
way unmolested. There is huge usefulness here, and selec-
tion can well be the steadfast maintainer of the viceroy’s
dissimulation. But of what avail for this purpose of deceit
was the first tiny tinge or fleck of red-brown on the staring
black and white wings of the ancestral viceroy? How can
one possibly conceive of an attainment of this identity of
pattern between mimicker and mimicked by selection on a
basis of life-or-death-determining advantage of slight chance
appearances of brown or reddish flecks or tinges in suc-
cessive viceroys? Not until practically full development of
the mimicry pattern existed can this pattern have worked its
advantage. It is, indeed, a different matter with many, per-
haps most, cases of general or special protective resemblance.
A little green, a little brown could obviously help the insect
living in green foliage, or on the ground. Every change of
tinge toward the general environing colour is worth while; it
helps melt the insect into its inanimate surroundings. But
with mimicry it must be the whole thing or nothing; or at
least near enough to the whole thing to pass for it. Wolff
puts the objection about as follows: There are compound
organs and complex adaptations, whose complication (he
would better say, whose advantage due to complication) can

DARWINISM ATTACKED. 51

only be reached by a leap, while the selection theory pre-
supposes slight gradual stages of complication.
Wolff ** expresses another phase of this objection by re-
ferring to a few of many cases of complex relations between
Difficulty og entirely distinct organs in the body, which
explaining com- relations constitute some of the most important
ae functions of the body. For the successful
parts by selec- establishment of these relations it has been
tion. ,
necessary, as Wolff expresses it, “that for each
advance in development or complexity of one definite pecu-
liarity in an organ there must appear corresponding and
exact definite advance in development or complexity of a
peculiarity in another entirely distinct organ.” Wolff’s first
example is the relationship existing between the muscles
and nerves of the higher animals. The intimate, delicate,
and precise character of the relations between the nerve-end-
ings and the muscle cells, to be explicable by selection of
fortuitous variations, must have required coincident varia-
tions both in structure and functions of each muscle cell and
each nerve-ending that are impossible to conceive of. “It
might be,” says Wolff, “possible to picture the gradual
development of the relations between one muscle cell and
one nerve-ending on the basis of a selection among infinitely
fortuitous variations, but that such variation shall occur
coincidently in time and character in hundreds or thousands
of cases in one organism is inconceivable.”
In the case of organs whose functions are regulated from
a common centre, the development of centre and of organs
must have gone on coincidently and could not have been
independent. The development of the eye is useless if
the development of the optic centre did not go hand in
hand with it. Without the one the other has no reason,
no significance, therefore selection could have brought
neither to its proper development independently. The
coincident appearance, however, of organ and centre can

52 DARWINISM TO-DAY.

be explained by the selection theory only when there is
postulated a definite degree of complexity of the fortu-
itously appearing slight variations, that is, when this
theory is in condition to assume that which would be a
denial in terms that variations are wholly fortuitous.
Wolff goes on to give certain examples of such complex
relations which involve a dependence of the use upon an
instinct, as the performance by the queen honey-bee of her
particular functions in the hive, etc. ,

“Out of this discussion,’ says Wolff, “finally we must
postulate that structures which are to be explained by the
selection theory must possess at the least two certain charac-
teristics. Such a structure, namely, must occur but once
in an organism [that is, must not be a serially or bilaterally
repeated organ, nor indeed appear in any condition of plural
number]; further, it must not stand in any necessary relation
to any other part of the same organism, that is, in a relation
which one can interpret as a relation not existing from
the beginning, therefore one which must be looked on as an
acquired relation. But if we survey the whole animal king-
dom it will be very difficult for us to find any structures
which satisfy both these requirements. It might be possible
to find some which perhaps seem to satisfy the second re-
quirement, but with regard to the first requirement I may
declare,” says Wolff, “that there is scarcely a single structure
which fulfils it. Symmetry alone, which rules almost all
organisms, makes organs which appear in the singular num-
ber rarities, and even such as the pancreas, etc., are com-
posed of many finer structures, which are homodynamous
among themselves. When we find two similar organs in
different animal groups we seek for a causal explanation of
this similarity and find it in common ancestry. It is absurd
to seek a causal explanation for the origin of homologous
structures and yet postulate a purely chance or fortuitous
explanation for the origin of homodynamous structures.”

2
s
c
:

;
’

DARWINISM ATTACKED. 53

Another objection which the study of the utility of col-
our and pattern ** also has impressed upon me is that of the

Pbisdtita based carrying too far of certain lines of modification.
on over-speciali- Classic examples are the fatal over-development
saa of the antlers of the extinct Irish stag, the un-
wieldiness of the giant Cretaceous reptiles, the intimate
identity of the halves of bilaterally symmetrical animals.
Let me call attention to an overdone case of “protective
resemblance’ among the insects. It is that of the famous
Kallimas, the dead-leaf butterflies of the Malayan and gen-
eral south tropical regions. These butterflies (there are
several species which show the marvellous imitation) have
the under sides of both fore and hind wings so coloured and
streaked that when apposed over the back in the manner
common to butterflies at rest, the four wings combine to

Kellima, the resemble with absurd fidelity a dead leaf still
dead-leaf butter- attached by a short petiole to the twig or branch.
a I say absurd, for it seems to me the resemblance
is over-refined. Here for safety’s sake it is no question of
mimicking some one particular kind of other organism or
inanimate thing in Nature which birds do not molest. It is
simply to produce the effect of a dead leaf; any dead leaf;
a brown, withering leaf on a branch. Leaf-shape and gen-
eral dead-leaf colour scheme are necessary for this illusion.
But are these following things necessary? namely, an
extraordinarily faithful representation of mid-rib and lateral
veins even to faint microscopically-tapering vein tips; a
perfect short petiole produced by the apposed “tails” of the
hind wings; a concealment of the head of the butterfly so
that it shall not mar the outlines of the lateral margin of the
leaf; and, finally, delicate little flecks of purplish or yellow-
ish brown to mimic spots of decay and fungus-attacked spots
in the leaf (!) and, as culmination, a tiny circular clear
spot in the fore wings (terminal part of the leaf) which shall
represent a worm-eaten hole, or a piercing of the dry leaf

54 DARWINISM TO-DAY,

by flying splinter, or the complete decay of a little spot due
to fungus growth! A general and sufficient seeming of a
dead leaf, object of no bird’s active interest, yes, but not a
dead leaf modelled with the fidelity of the wax-workers in
the modern natural history museums. When natural selec-
tion had got Kallima along to that highly desirable stage
when it was so like a dead leaf in general seeming that
every bird sweeping by saw it only as a brown leaf clinging
precariously to a _ half-stripped branch, it was natural
selection’s bounden duty, in conformance with its obligations
to its makers, to stop the further modelling of Kallima and
just hold it up to its hardly won advantage. But what
happens? Kallima continues its way, specifically and ab-
surdly, dead-leafwards, until to-day it is a much too fragile
thing to be otherwise than very gingerly handled by its
rather anxious foster-parents, the neo-Darwinian selec-
tionists.

An objection which was long ago pointed out, and which
has been emphasised strongly by some biologists and almost

overlooked by others, is that of the incom-
Soe patibility of the results concerning the age of
selection oppor- life on this earth as propounded by physicists
sind tedoits and astronomers with the demand made by the

theory of descent. This objection of the lack
of time for the production of the hosts of kinds of plants
and animals through the slow workings of natural selection
was brought forward against Darwin from the very begin-
ning and has never been given up. De Vries,”’ for example,
in a recent paper, refers to it as follows:

“The deductions made by Lord Kelvin and others from the
central heat of the earth, from the rate of the production of
the calcareous deposits, from the increase in the amount of
salt in the water of the seas, and from various other sources,
indicate an age for the inhabitable surface of the earth of
some millions of years only. The most probable estimates

DARWINISM ATTACKED. 55

lie between twenty and forty millions of years. The evolu-
tionists of the gradual line, however, have supposed many
thousands of millions of years to be the smallest amount
that would account for the whole range of evolution, from
the very beginning until the appearance of mankind. This
large discrepancy has always been a source of doubt and a
weapon in the hands of opponents of the evolutionary idea,
and it is especially in this country that much good work has
been done to overcome this difficulty. The theory of descent
had to be remoulded. On this point conviction has grown
in America during the last decades with increasing rapidity.”

However (according to a newspaper clipping), Professor
Lankester,” a present-day Darwinian champion, in the

aoe of an interesting outline of the advance-
sibleanswerto ment of science in the past twenty-five years
the objection. == Which he gave at the opening meeting of the
British Association at York recently (September, 1906)
again raised the question of the age of the earth. Refer-
ring to the discovery of radium as one far exceeding in
importance all other modern scientific discoveries he said
that if the sun contained a fraction of one per cent. of radium,
this radium would account for and make good the heat that
is annually lost by the sun. “This is a tremendous fact,
upsetting all calculations of physicists as to duration in past
and future of the sun’s heat and the temperature of the
earth’s surface. The geologists and the biologists have long
contended that some thousand million years must have
passed during which the earth’s surface has presented ap-
proximately the same conditions of temperature as at pres-
ent, in order to allow time for the evolution of living things
and the formation of aqueous deposits of the earth’s crust.
The physicists,’ contended Professor Lankester, “notably
Professor Tait and Lord Kelvin, refused to allow more than
ten million years (which they have subsequently increased
to a hundred million, basing the estimate on the rate of

56 DARWINISM TO-DAY.

cooling of a sphere of the size and composition of the earth).
They have assumed that its material is self-cooling. But
as Huxley pointed out, mathematics will not give a true
result when applied to erroneous data. It has now, within
the last five years, become evident that the earth’s material
is not self-cooling, but on the contrary self-heating, and
away go the restrictions imposed by physicists on geological
time. They are now willing to give us not merely a thou-
sand million years, but as many more as we want.”

In this connection should be mentioned the position taken
by Ammon *’ and others who argue that the real effect or

Claim that se. result of natural selection is to preserve the
lection hinders type at the expense of the variants, which would
rather than pro- ~ ;
motes species: Make it a retarder rather than accelerator of
change, species-change. Bumpus’s ** observations on,
and conclusions concerning, his storm-beaten English spar-
rows is an example of what Ammon claims must be the
real result of selection. Bumpus, in statistical studies of the
variation of two animal species introduced from Europe into
the United States, viz., the English sparrow and the peri-
winkle, Littorina littorea, shows that the eggs of the sparrow
and the periwinkles themselves are much more variable in

Bengurk cb America than in their native regions, and the au-
servationson thor attributes this increased variability to their
ai ies “presumable emancipation from many of the re-
straining influences of natural selection.” In the case of the
English sparrows, also, Bumpus believes himself able to
show on a basis of the examination of 136 birds brought
in wounded or stunned after a severe storm of snow, rain,
and sleet (Feb. 1, 1898), that the sixty-four birds that
perished (seventy-two revived), “perished not through acci-
dent, but because they were physically disqualified, and that
the birds which survived, survived because they possessed
certain physical characters. These characters enabled them
to withstand the intensity of this particular phase of selective

DARWINISM ATTACKED. 57

elimination and distinguish them from their more unfortu-
hate companions.” The fortunate characters were mas-
culinity, shortness of body, lightness, longer humerus, longer
femur, longer tibio-tarsus, longer sternum, greater brain
capacity. But more important for survival than favourable
variations was the fact of’ approach to the species type or
mode of variability. The extreme variants perished.
“The process of selective elimination is most severe with ex-
tremely variable individuals, no matter in what directions the
variations may occur. It is quite as dangerous to be con-
spicuously above a certain standard of organic excellence
as it is to be conspicuously below the standard. It is the
type that nature favours.”

APPENDIX,

* For a fairly complete bibliography, with excellent abstracts, of
all important critical discussions of Darwinism since 1895, see
L’Année Biologique (ed. Y. Delage), 1895-1903; for good bibliog-
raphy also see Zoologischer Jahresbericht, issued annually. See
also discussions and notes in such journals as Natural Science, Bio-
logisches Centralblatt, Nature, Science, American Naturalist, etc.

*Von Kolliker, A., “Uber die Darwin’sche Schépfungstheorie,”
Zeitsch. f. wiss. Zool., Vol. XIV, pp.. 174-186, 1864.

® Korschinsky, S., “Heterogenesis und Evolution,’ Naturw. Wo-
chenschrift, Vol. XIV, pp. 273-278, 1899.

*Morgan, T. H., “Evolution and Adaptation,” 1903. A vigorous
anti-Darwinian argument, somewhat sophisticated in its lawyer-
like handling of Darwin’s own words, but keen and trenchant in
its exposure of the weaknesses of the selection theories as species-
forming explanations. It is also a brief for de Vries’s theory of
species-forming by mutation. (See chap. xi of this book.)

° “See Osborn, H. F., “Biol. Lectures,” Wood’s Holl Lab., 1894,
Pp. 79-100, for suggestive plea for the recognition of “the unknown
factors of evolution.”

© The subject of variation, an absolutely fundamental one in any
consideration of the factors and mechanism of organic evolution, has
a very large literature pertaining to it which the
serious student of evolution must make considerable
acquaintance with at the very outset. Of this litera-
oo the following books and papers may be suggested to serve aS

Books and pa-
me on variation,

58 DARWINISM TO-DAY.

a means of introduction to the subject, not alone in its broad out-
lines, but in its extensive ramifications of relation to other evolution
problems. Some of these books and papers include extended biblio-
graphic lists sufficient to enable one to follow up the subject in any
of its special phases.

Darwin, Chas., “The Origin of Species,” 1859.

Darwin, Chas., “The Variation of Animals and Plants under
Domestication” (Amer. ed.), 1868.

Wallace, A. R., Darwinism,” chaps. iii and iv, 1891.

Allen, J. A., “On the Mammals and Winter Birds of East Florida,”
Bull. Mus. Comp. Zool., Il, pp. 161-450, Plates IV-VIII, 1871.

Galton, F., ““Natural Inheritance,” 1880.

Bateson, W., “Materials for the Study of Variation,” 1894.

Duncker, G., “Die Methode der Variationsstatistik,” Archiv f.
Entwick. Mech., Vol. VIII, pp. 112-183, 1899. (Full bibliography.)

Rosa, D., “La riduzione progressiva della variabilita i suoi rap-
porti coll’ esstinzione e coll’ origine delle specie,” 1899.

Conn, H. W.. “The Method of Evolution,” chap. iv, 1900.

Davenport, C. B., “A History of the Development of the Quan-
titative Study of Variation,” Science, N. S., Vol. XII, pp. 864-870,
1900.

De Vries, H., “Die Mutationstheorie,” Vol. I, pp. 7-150, pp.
412-648, I90I.

Ewart, J. C., “Variation; Germinal and Environmental,” Trans.
Roy. Dublin Soc., Ser. II, Vol. VII, pp. 353-378, 1901.

Vernon, H. M., “Variation in Animals and Plants,” 1903.

Delage, Y., “L’Hérédité,” pp. 283-310, pp. 826-843, 2d ed., 1903.

Davenport, C. B., “Statistical Methods in the Study of Varia-
tion,” 2d ed., 1904. (Full bibliography. )

Kellogg and Bell, “Studies of Variation in Insects,” Proc.
Wash. Acad. Sci., Vol. VI, pp. 203-332, 1904.

Lotsy, J. P., “Vorlesungen ttber Descendenztheorien,” Vol. I,
chap. 1x, 1906.

Biometrika, 1go1-1906. A journal devoted chiefly to the sta-
tistical study of variation.

"See Kellogg, “Variation in Parthenogenetic Insects,” Science,
N. S., Vol. XXIV, pp, 695-699, 1906, in which it is shown that the

Cases of marked Parthenogenetically produced drone honey-bees vary
variation in par- Much more than do the workers which are of bi-
thenogenetic ani- sexual parentage, and that parthenogenetically pro-
mals. duced plant-lice (Aphidids) vary as markedly as
insects of bisexual parentage. See also Warren, Proc. Roy. Soc.,
Vol. LXV, 1899. in which the variation in parthenogenetic varia-
tions of Daphnia magna is shown to be little, if any, smaller than

DARWINISM ATTACKED. 59

jin sexually produced generations; also, Biometrika, Vol. I, pp. 129-
154, 1902, in which Warren shows the variation in parthenogenetic
series of the plant-louse Hyalopterus trirhodus to be as large as
the variability exhibited in sexual forms.

See also Haycraft, J. B., “The Role of Sex,” Nat. Science, Vol.
VII, pp. 245-250, 342-344, 1895, in which paper is presented an ingen-
ious argument to show that sexual reproduction tends not merely not
to increase variation but to decrease it: “the convergence to the mean
is, then, a result of sexual reproduction: it may be termed the role
of sex, and one indeed of no secondary order. The tendency con-
stantly to vary is a property inherent in protoplasm, yet often for
long periods of time the environment may be the same. In order
that a species may continue to live in such a constant environment,
the effects of variation must be checked. Sexual multiplication, a
conservative function, antagonises the progressive tendency of varia-
tion: *

Other naturalists have also held strongly to this view of the role
of amphimixis. See Bailey, L. H., “The Plant Individual in the
Light of Evolution,” address before the Biological Society of Wash-
ington, January 12, 1895, Science, N. S., Vol. I, p. 281, 1895, in which
paper the author points out the importance of a clear recognition
of the tremendous possibilities and actuality of asexual variation
in plants.

In a paper by Winslow and Rogers (Science, N. S., Vol. XXI,,
p. 486, 1905), referring to the classification of bacteria, there is the
following statement: ‘Since the swamping of minor differences by
sexual reproduction is absent from bacteria, every inheritable
variation is maintained, and instead of true species, we find an infi-
nite series of minutely differing but constant races. The only prac-
tical method of handling and systematising these, is to establish cer-
tain fairly distinct groups and types about which the individual
‘variations may be grouped.”

* By using a large series of individuals, and carefully tabulating
the noted conditions of variation of one or more parts, using, pref-

Nae erably, attributes whose variability is capable of being
pets hea mathematically expressed, such as dimensions, num-
of probabilities, bers of spines, or spots, etc. many students have

shown that these variations seem to occur in most
‘cases according to the law of probabilities, and that a curve plotted
so as to express graphically the actual conditions of variation for a
given character would be nearly identical with the curve that could
be plotted so as to express what variation would exist in the given
case if this variation occurred exactly according to the laws of
chance. This means that in a thousand individuals collected at

60 DARWINISM TO-DAY.

random and examined for variation in any character, say total
length of body, not only would there be found a larger number of
individuals of medium length than of any other length between the
two extremes, represented by the longest and shortest individuals,
but that the various lengths between the mean and the longest and
between the mean and the shortest, would be represented by groups
of individuals regularly decreasing in number as the length in-
creased or decreased on either side of the mean, but of equal number
if compared at equal amounts of difference away from the mean.
The curve expressing graphically the law of probabilities or,
better, the frequency of error, is determined by the formula for this
frequency deduced originally by Gauss at the beginning of the last
century. It would lead us too far afield to reproduce here the
mathematical proof of the formula or method of its determination,
but Vernon’s excellent concrete illustration of how such a formula
could be deduced directly from a study of biologic variation
may be quoted. “Supposing,” says Vernon in “Variation in Animals
and Plants,” pp. 11 and 12, 1903, “a group of developing organisms
be taken, of which the growth can be affected in a favourable or an
unfavourable manner by their surroundings. Let us suppose that
there are twenty different agencies, each of which would produce
an equal, favourable effect on growth, and twenty which would pro-
duce just as great an effect in the opposite direction. Suppose, also,
that each organism is subjected to only half of these forty different
agencies; then it would follow, according to the laws of chance,
that a larger number of the organisms would be acted upon by 10
favourable and to unfavourable agencies, than by any other com-
bination; @.e., they would, on our hypothesis, remain absolutely
unaffected in their growth. A somewhat smaller number would be
acted upon by 11 favourable and 9 unfavourable agencies, or on the
whcle, would have their growth slightly increased. A still smaller
proportion would be acted on by 12 favourable and 8 unfavourable
agencies, or would have their growth rather more increased. Finally,
the number of organisms acted on by 20 favourable and o unfa-
vourable agencies would be extraordinarily small, but in this case the

effect on growth would be extremely large. Similar relationships, ~

only in the reverse direction, would of course be found in those
cases in which the number of unfavourable agencies exceeded the
number of favourable. If desired, the proportional numbers of organ-
isms acted on by all the different combinations of agencies may be
readily determined by expanding the binomial (% + %)’°. It
is found, for instance, that for each single time the organisms are
acted on by the whole 20 favourable agencies, they are acted on 190
times by 18 favourable and 2 unfavourable; 15,504 times by I5

DARWINISM ATTACKED. — 6r .

favourable and 5 unfavourable; and no less than 184,756 times by
10 favourable and 10 unfavourable. Let us consider that the organ-
isms acted on by 20 favourable and o unfavourable agencies have
their size increased 20 per cent.; those acted on by 15 favourable
and 5 unfavourable by 15 — 5 = Io per cent.; and so on. If now
these percentage increments and decrements be plotted out at equal
distances on a base line, and” ordinates corresponding to the theo-
retical frequencies erected from each, then by joining these ordinates
we shall obtain a curve which is practically identical in form with
the probability curve of the law of frequency of error. Thus, by a
simple arithmetical method, we obtain a series approximating more
and more closely to the probability curve, the greater the number
of times the expression (% + %) is expanded. Expanded 20
times, the average error is less than .5 per cent., and for a greater

number of times it becomes rapidly smaller and smaller.”
This discovery and formulation of the law of individual varia-
tion—namely, that such variation occurs according to the law of
probabilities—was first made by the Belgian anthro-

Quetelet, the ; sf por

Meravccoretvaric DOlOgISt, Quetelet (‘‘Lettres sur la théorie des Proba-
ation according bilités,’ Brussels, 1846), on a basis of the examina-
‘to the law of tion of the height and chest measurements of soldiers.
chance. It was later elaborately confirmed by Francis Galton
(numerous papers and the book, “Natural Inheritance,” 1870-1890),
by quantitative determinations of the height, weight, span of arms,
breathing capacity, strength of pull, strength of squeeze, swiftness
of blow, and keenness of sight in men and women. It has been
most illuminatingly discussed by Karl Pearson in ‘‘The Chances of
Death, and other Studies in Evolution,” 2 vols., 1897. Since then
the recognised necessity of a more thorough study and understand-
ing of variation, as the indispensable foundation of species-forming
has led to a large development of the statistical and mathematical
study of variation, under the name of biometry, a study largely due
to the initiative and genius of the English mathematician and natural
philosopher, Karl Pearson (numerous papers from 1894 to present).
Most of the methods and formule for determining precise mathe-
matical expression of variation conditions have been devised by him.
These methods and formule permit of an actual mathematical com-
parison of variation among various parts in one species (immensely
enlarging our definite knowledge of structural correlations), or
among similar or wholly different parts in various species. With
the statistical facts or data of variation thus put into precise mathe-
matical expression, these expressions may be submitted to a deal
of independent mathematical treatment; rather bewildering, it must
-be confessed, to most biologists, but presented by the biometricians

62 DARWINISM TO-DAY.

as the first step toward making biology, in part, at least, an exact
science. But there is no question at all that the statistical and
quantitative study of variation, and the use of authoritatively
deduced mathematical expressions (and the graphic representation
of these by plotted frequency curves, polygons, etc.), have immensely
advanced our understanding of variation conditions, and given us.
definiteness and concreteness in a fiindamental field of evolution
study, where before were a mass of uncoordinated data and a haze
of loose generalising.

* Bateson, Wm., “Materials for the Study of Variation,” 1894.

*® See Kellogg and Bell, ‘Studies of Variation in Insects,” Proc.
Wash. Acad. Sct., Vol. VI, pp. 203-332, 1904, in which are discussed.
(pp. 257-273) variation conditions existing in the lady-
esind gee bird beetle, Hippodamia convergens. The variations.

in the number and character of the elytral pattern
(small black spots on a brown ground) noted in a thousand speci-
mens examined, were such that eighty-four “aberrations,” or pat-
tern-variates, could be distinguished and described, and yet, an
intensity of scrutiny demanding the use of a lens was necessary to:
distinguish properly these varying types. Such a scrutiny, needless.
to say, will never be given these beetles by bird or lizard, the active
agents representing natural selection, as far as pattern is to be
tested. Nevertheless, these pattern variations, if not so completely
connected by gradatory steps, would be exactly the characters on
which several Hippodamia species would be based, for they range all
the way from no spots to eighteen spots, although twelve is the
species character of convergens.

** Romanes discusses this subject of the indifference, or triviality,.
of many specific characters at some length in chap. vii of his “Dar-
win and After Darwin,” II, ‘““Post-Darwinian Questions,” “Heredity
and Utility,” 1895.

** Conn, H. W., “Method of Evolution,” pp. 78-83, 1900.

** Nageli, Carl, ‘“Mechanisch-physiologische Theorie der Abstam-
mungslehre,”’ 1884. Nageli, an eminent botanist, formulated many

Nageli’s seven Years ago the following famous seven objections to
objections to spe- the natural selection theory of species-forming (pp.
cies-forming by 289-290) :
selection, “Tech hebe folgende sieben Gesichtspunkte hervor,
welche uns die Abstammung durch Zuchtwahl unannehmbar machen :

“tT. Bezuglich der allgemeinen Bedeutung der Selectionstheorie
ist die unbestimmte Wirkung unbestimmter Ursachen und die dem
Zufall allzusehr tiberlassene Entscheidung durch die nattrliche
Zuchtwahl unserem naturwissenschaftlichen Bewusstsein weniger
zusagend. Ferner setzt sich die Selectionstheorie, welche ihrem

DARWINISM ATTACKED. 63

Princip gemass nur nach dem erreichten Nutzen einer Erscheinung
fragt, um dieselbe zu rechtfertigen, in Widerspruch mit der wahren
und exacten Naturforschung, welche vor allem die bewirkenden Ur-
sachen der Dinge zu erkennen sucht.

“2. Die Folgerung von der (kiinstlichen) Rassenbildung auf die
(nattrliche) Varietatenbildung, welche die Grundlage der Selec-
tionstheorie ausmacht, ist unzulassig, da beide wesentlich verschie-
den sind und namentlich sich riicksichtlich der Kreuzung ungleich
verhalten. Die Varietaten namlich vermischen sich sehr schwer mit
einander und nehmen kein fremdes Blut in irgend wirksamer Menge
auf, werden somit auch durch die ihnen gebotene Gelegenheit zur
Kreuzung nicht verandert; mit diesen Eigenschaften stimmen ihre
Vorkommensverhaltnisse genau tberein.

“3. Nutzliche Veranderungen kénnen erst, wenn sie eine bemerk-
bare Hohe erreicht haben und in zahlreichen Individuen vorhanden
sind, eine ausgiebige Verdrangung der Mitbewerber bewirken. Da
sie aber im Anfange durch eine lange Reihe von Generationen jeden-
falls noch sehr unbedeutend und nach der Selectionstheorie auch nur
in einer kleinen Zahl von Individuen vertreten sind, so bleibt die
Verdrangung aus und eine nattirliche Zuchtwahl kommt, da ihr der
wirksame Hebel mangelt, uberhaupt nicht zu Stande.

“4. Die Ernahrungseinflusse, welche die Selectionstheorie voraus-
setzt, bewirken thatsachlich keine erblichen Veranderungen, und
wenn sie es thaten, so konnte eine Steigerung der begonnenen Abian-
derung nicht eintreten, weil die unvermeidliche Kreuzung eine
naturliche Zuchtwahl unmoglich machen wiirde. Ferner lasst sich
aus den unbestimmten, in allen denkbaren Richtungen wirkenden
Ernahrungseinfllissen der so stetige phylogenetische Fortschritt zu
einer complicirteren Organisation nicht erklaren. Ebenso wenig
werden durch dieselben die Erscheinungen der Anpassung verur-
sacht; dies ergibt sich einerseits aus dem Umstande, dass Gebrauch
und Nichtgebrauch die Zu- und Abnahme der Organe bedingen, da
diese Ursache fiir sich vollkommen ausreicht und daher die Mit-
wirkung einer zweiten andersartigen Ursache ausschliesst,—und
andrerseits durch den ferneren Umstand, dass Anfange von Organen
bis zu der Grosse, wo sie in Gebrauch kommen und ihre Nuitzlich-
keit zu erproben verm6gen, mangeln, obgleich sie durch die Ernah-
rungseinfitisse in Menge hervorgebracht werden mussten.

“5. Die Ejigenschaften der Organismen mtssten in Folge der
naturlichen Zuchtwahl um so constanter sein, je ntitzlicher sie sind,
und Einrichtungen, die keinen Vortheil gewahren, konnten keine
Bestandigkeit erlangen. Im Widerspruche hiermit gehGren gewisse,
rein morphologische, mit Ricksicht auf den Nutzen indifferente
Merkmale zu den allerbestandigsten.

64 DARWINISM TO-DAY.

“6. Aus der Selectionstheorie, nach welcher von den eintretenden
richtungslosen Veranderungen bloss die ntitzlichen festgehalten wiir-
den, lassen sich weder die Divergenz der Reihen in den organischen
Reichen, noch die bestehenden Lucken in und zwischen den Reihen
erklaren, indem vielmehr eine netzformige Anordnung der Sippen
zu Stande kommen musste.

‘7 Ebenso widersprechen jener Theorie das Nichtvorhandensein
der von ihr behaupteten gegenseitigen Anpassung der Bewohner eines
Landes und die bestehenden Naturalisationen fremder Erzeugnisse.

“Diese Einwtirfe gegen die Selectionstheorie, die ich hier bloss
ganz allgemein formulirt habe, sollen im folgenden des Naheren
begriindet werden.”

*4 Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” 1808.
From this caustic attack on the Darwinian position, I quote as fol-
lows (pp. 56-57):

“Wenn wir sagen, die Selektion schafft Zweckmassiges dadurch,
dass eben nur das Zweckmassige erhalten wird, das andre zu Grunde

geht, so wird in dieser Fassung das Zweckmassige

Wolff's attack nattirlich vorausgesetzt, aber nicht sein Zustandekom-
on the selection~- men erklirt. Dass Zweckmissiges iiberhaupt da war,
ists’ assumption ... ‘ ie
of the appearance 1st im héchsten Grade unwahrscheinlich und unver-
at the right time Standlich. Mochte auch unter den vielen Variie-
of the needed rungen manchmal etwas Zweckmassiges zufallig
Variation. vorgekommen sein, so ist die Wahrscheinlichkeit eines

solchen Eintreffens so gering, dass ich nicht das Recht
habe, diesen Faktor als einen gegebenen in meine Rechnung ein-
zusetzen. Diese Wahrscheinlichkeit sucht nun der Darwinismus
dadurch zu vergrossern, dass er alle moglichen Falle annimmt, unter
welchen nattrlich auch das Zweckmassige als Spezialfall enthalten
sein muss. Der Darwinismus sucht also den Treffer sich dadurch
zu sichern, dass er den ganzen Gluckshafen mit nach Hause nimmt.

“Um ein Beispiel zu nehmen: es sei von Vorteil, dass die Schna-
belform entsteht, wie sie beim Kreuzschnabel vorhanden ist. Der
Darwinismus nimmt an, dass durch gluckliche Variierung ein bezw.
mehrere oder sogar viele gekreuzten Schnabel auftraten. Sagt nun
der Gegner: das spontane Auftreten einer Schnabelkreuzung scheint
mir so unwahrscheinlich, dass ich diese Voraussetzung eben nicht
zugebe, so antwortet der Darwinist: unter allen mdglichen Schnabel-
varlierungen ist auch der gekreuzte, darf ich alle, so darf ich auch
diesen voraussetzen; da aber die Variierung, wie die Beobachtung
lehrt, nach allen Richtungen beliebig wirkt, so sind alle Variierungen
moglich, folglich darf ich auch jene spezielle voraussetzen.

“Der Gegner wtirde jetzt vielleicht so erwidern: Gewiss, moglich
sind alle Variierungen, aber gegeben ist deren doch immer nur eine

DARWINISM ATTACKED. 65

begrenzte Anzahl. Die Zahl aller moglichen Variierungen ist = ©,
die Zahl der gegebenen ist eine endliche Grosse. Die Wahrschein-
lichkeit des Ejintretens einer speziellen zweckmassigen Variierung
(in unserm Beispiel der zweckmassigen Schnabelkreuzung) ist End-
liches dividiert durch Unendliches, d. h. eine Zahl, welche sich der
' Null ohne Ende nahert; mithin ist die Wahrscheinlichkeit, dass
unter den gegebenen Fallen sich eine gtinstige Variierung befindet,
so ungeheuer klein, dass nicht die geringste wissenschaftliche Be-
rechtigung besteht, den betreffenden Fall vorauszusetzen. Und nun
witirde allerdings demjenigen Darwinisten, welchem die Ktihnheit
fehlte, die Zahl der ihm zur Verfuigung stehenden Variierungen ein-
fach = © zu setzen, wohl kaum etwas andres tbrig bleiben, als sich
darauf zu berufen, dass es eine Sorte von Variierungen giebt, bei
denen die Zahl der gegebenen Falle gross genug ist, um alle mogli-
chen zu enthalten, gross genug also, um die Voraussetzung jedes
einzelnen wissenschaftlich zu rechtfertigen, namlich diejenigen Vari-
ierungen, welche nur in graduellen Veranderungen bestehen, bei
denen es sich also nur darum handelt, dass ein Vorhandenes grosser
oder kleiner wird. Hier ist die Zahl der modglichen Falle gleich 2,
die der gegebenen ebenfalls, die Wahrscheinlichkeit, sich unter den
gegebenen zu befinden, ist also ftir jeden der mdglichen Falle
gleich 1.”

** Kronig, “Das Dasein Gottes und das Gliick des Menschen,” p.
109, 1874.

** Weismann, Aug., “On Germinal Selection as a Source of Defi-
nite Variation,” trans. McCormack, p. 3 (preface), 1896.

*" Pfeffer, Georg, “Die Umwandlung der Arten,” 1894.

** Wolff, G., “Der gegenwartige Stand des Darwinismus,” 1896;
also, “Beitrage zur Kritik der Darwin’schen Lehre,” 1808.

*® Morgan, T. H., “Evolution and Adaptation,” 1903.

*’ Kellogg and Bell, “Studies of Variation in Insects,’ Proc.
Wash. Acad. Sci., Vol. VI, pp. 203-332, 1904. The following is
quoted from pp. 330-332:

“Insects are bilaterally symmetrical and metameric animals. There
are thus right and left and fore and aft structural correlations. Do the

Example of non- variations, continuous and discontinuous, show similar
correlated varia- bilateral and metameric correlation? Evidence regard-
bility in bilater- ing this question will be found on many pages in the
ane present paper, right and left correlation, at least, hav-

ing been considered and briefly discussed in connection
with almost all of the various cases studied. And the evidence is
curiously conflicting. For example, in the male black ant in which
were studied the variations of the venation and number of hooks, a
close correlation in the variation conditions of right and left wings

66 DARWINISM TO-DAY.

exists. On the other hand, in the honey-bee the bilateral correla-
tion of variation seems surprisingly small (see pp. 214-222). In
the case of variations in pattern, also, there is no uniformity among
the various cases studied. In Hippodamia convergens (p. 257 et
seq.) the two elytra show pattern-variations quite independently ;
in Diabrotica soror (p. 274 et seq.), on the contrary, there seems
to be a marked right and left correlation in the elytral pattern-
variation. In the cases of the variation in number of tibial spines
on the right and left hind tibie of locusts (p. 301) and cicadas (p.
306), we have simply made a brief statement, in each case, of the
actual conditions of correlation, leaving the reader to draw his own
conclusions. In the case of the variation in actual and relative
length of the antennal segments of the scale insect, Ceroputo yucce
(?) (p. 310), there is a surprising lack of correlation between the
right and left antenne.

““We have not attempted to determine the mathematical expression
(coefficient of correlation) for any of the cases studied. The data
presented, however, will enable any biometrician, who sees an
advantage in doing this, to do it. But without checking our results
by the use of that method there seems, on the whole, to be a sur-
prising lack of that fine degree of correlation in variation which
we should expect to find existing, if we believe that the actual
existing conditions of structure and pattern in these bilaterally sym-
metrical animals are an expression of the result of the action of
a rigorous natural selection. If one condition of pattern or structure
is the most advantageous (of the many conditions which selection
among a host of fluctuating variations could have established),
surely this condition ought to be pretty closely similar on both sides
of the insect. That as much bilateral variety as actually exists,
in many of the species examined by us, should exist—a variety
comparable in certain cases even with the degree of variety revealed
by the comparison of considerable series of individuals—is a state of
affairs that only confirms us in the belief that these innumerable
small continuous variations, on which for so long the thorough-
going selectionists have put their faith as the sufficient bases for
natural selection’s species-forming work, are clearly not competent
to serve as such bases. If these ‘continuous’ variations are the foun-
dation stones of new species, some other agents than selection must
be found or invoked to build several courses on them, to produce
some cumulation of them, before natural selection finds them of
that life-and-death worth which is the prerequisite for her potent
interference.”

*? Henslow, the botanist, has maintained a constant attitude of
antagonism to natural selection on the basis of his belief that the

DARWINISM ATTACKED. 67

complex correlations of floral structures cannot possibly be accounted
for by the natural selection of fortuitous variations. Henslow’s
Whe clow's tn- observations and ideas are exploited in detail in
tagonism to selec- two books called, “The Origin of Floral Structures
tion as explain- through Insect and Other Agencies,’ 1895, and

_ eroffloral corre- “The Origin of Plant Structures by Self-Adaptation

sasions. to the Environment,” 1895.

72 Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” p.
6, 1808.

*8 Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” 1898.
I quote the following, pp. 6-8:

“Solche Erscheinungen, welche der Erklarung durch die Selek-
tionstheorie widerstreben, weil sie hier eine gesetzmassige kom-

plizierte Veranderung der Formen voraussetzen wurde,

Wolff's objection statt sie zu erklaren, sind aber nicht etwa nur verein-
to the necessary 7elte Fille, sondern von solchen wird die ganze
Sa Formgestaltung beherrscht, wie z. B. von symme-
incident varia- trischer Anlage. Auch brauchen wir uns bei dieser
tion in repeated Betrachtung nicht nur auf solche Gebilde zu_be-
structures as schranken, die in geringer Mehrheit vorhanden sind,
ae scaler, sondern es giebt ja Gebilde, die in hundert-, ja tau-

sendfacher Anzahl an einem und demselben Or-
ganismus sich finden, wie Schuppen, Haare, Federn. Betrachten
wir z. B. gerade die Federn. Wie viel Millionen Variierungen
musste eine Reptilienschuppe durchmachen, bis sie sich in eine
Feder verwandelt hatte, vollends noch in ein so kompliziertes Gebilde
wie z. B. die Schwanzfeder des Pfaues. Aber dies ware immer
noch nach der Selektionstheorie erklarlich. Nicht erklarlich dage-
gen ware, dass die anderen Schwanzfedern immer gleichzeitig
dieselben Variierungen durchmachten. Ein Gesetz, welches ein
einheitliches Variieren dieser Hautgebilde vorschreibt, giebt es
nicht, denn es variieren ja nicht alle gleich. Es entstehen viele
gleiche Flaumfedern, viele gleiche Schwanzfedern etc., an einigen
Stellen bleiben die Schuppen sogar erhalten, namlich an den hinteren
Extremitaten.

“Wir konnen noch weiter gehen. Eine Masse von einzelnen Zel-
len musste bei den verschiedenen Differenzierungen, bei Entstehung
des Darms, des Nervensystems, der Muskulatur etc. in ganz genau
der gleichen Weise variieren. Wenn wir hier die Selektionstheorie
zur Erklarung herbeiziehen wollen, so ist die Kompliziertheit des
einzelnen Variierungsinkrementes so gross, dass damit die ganze
weitere Erklarung tberflissig wird.

“Interessant sind ferner solche homodynamen Gebilde, die nicht
zu gleicher Zeit auftreten, wie der dritte halbzirkelformige Kanal

!
\
i
|
'

68 DARWINISM TO-DAY.

im Gehororgan der Wirbeltiere, welcher bekanntlich erst in der
Klasse der Fische auftritt. Dieser dritte Kanal ist den beiden
andern vollig gleich, hat Crista, Ampulle, Macula etc., ist aber
spater entstanden; die namlichen zufalligen Variierungen, die
stattfanden bei der Entstehung der beiden ersten Kanale, mussten
viele Generationen spater ganz genau in derselben Art sich wieder-
holen! Dass diese Variierungen wieder auftreten, dies erklart die
Darwinsche Lehre nicht; denn die Selektion kann ja keinen Ein-
fluss auf die Variierung ausuben.

‘“‘Aehnlich sind die Resultate der Kowalevskyschen Untersuch-
ungen tuber fossile Huftiere zu betrachten, welche sich auf die im
Lauf der phylogenetischen Entwicklung stattgehabten Umwand-
lungen des Extremitatenskelettes dieser Tiere beziehen. Hier kann
bekanntlich eine allmahlich eintretende Verringerung der Anzahl
der Metatarsal- und Metakarpalknochen sowie der Phalangen
verfolgt werden. Diese Verringerung tritt zuerst an den hintern,
erst spater an den vordern Extremitaten auf!”

°* A moth, Phryganidia californica, whose larve live abundantly
on the oak trees in California, shows very clearly how a conspicuous

Example of mal- disadvantage does not seem to interfere much with
adaptation in egg- Successful life; for the “success” of this moth is only
laying habit of too well proved by the serious injuries which it pro-
Phryganidia cali- quces, because of its great numbers, on the beautiful
fornica, a 4

trees it infests. For several years the live-oaks and
white oaks of the Santa Clara Valley were defoliated to a dangerous
extent. The life history of the moth is told in detail in ‘The
Californian Phryganidian,” by Kellogg and Jack, Proc. Cal. Acad.
Sct., Ser. 2, Vol. V, pp. 562-570, 1895. From this account I quote the
following: ‘‘Although most abundant on the live-oaks (Q. agrifolia),
the larve attack other oaks. We have found them on Quercus
lobata, Q. kelloggii, Q. dumosa, and Q. douglasti. The live-oaks in
this vicinity begin to put out new leaves about January I, but in
the case of many of the trees badly defoliated by the larve in the
autumn, new leaves appeared much earlier than the first of Janu-
ary. The wintering of the insect in a larval condition is only possi-
ble in the evergreen oaks, and they are thus the natural and usual
host of the pest. At the time of the hatching of the first of the
autumn brood of eggs (latter part of November), the leaves of the
deciduous oaks begin to fall. But, oddly, the eggs were found to
be deposited on the leaves of both the white oak and Douglas’s oak
(deciduous oaks), and the larve hatched only to die of starvation.
By this suicidal means the pest aids in depleting its own numbers.
The new leaves of the deciduous oaks appear about April 1, before
the eggs for the summer brood of larve are deposited. These eggs,

DARWINISM ATTACKED. 69

therefore, can safely be laid on the leaves of these trees, but the
eggs laid by the fall moths on the foliage of these trees give up their
young to certain destruction.”

25 Mivart, St. G., “On the Genesis of Species,” 1871.

*° Wolff, G., eBeltege zur Kritik der Darwin’schen Lehre,” p. 8
ff., 1898.

*7 In Piepers, M. C, “Mimikry, Selektion und Darwinismus,”
1903, the author strongly antagonises the Darwinian explanation

Pi ; of protective warning and mimicking colour patterns.

iepers’s an- : ; ae
tagonism to selec- Piepers claims to show (1) that the so-called mimicry
tion explanation is a phenomenon or appearance whose _ biological
of colour and pat- value is greatly over-praised; (2) that the causes of
tern of insects. this appearance are not entirely known, yet can in
most cases be very well explained without having recourse to this
natural selection theory; and (3) that, therefore, mimicry makes
natural selection in no wise necessary, and hence lends no basis
for its establishing. The author also, in a long discussion of nearly
one hundred pages, criticises adversely the selection theories and
Darwin in general. He holds that the Darwinian theory of species-
building from varieties is very ill-grounded, but finds also de
Vries’s mutations-theory incompetent to explain species, at least, in
the large degree in which they actually exist. The author presents
a theory or explanation of his own for species-forming, which is
essentially this: Variation is not simply a fluctuation about a stable
mean; it 7s evolution in small steps. Evolution is the principle of
life; it is determinate, i.e., progressive, yet with rapid, slow, or even
standstill periods. There are differences in the rapidity of evolu-
tion among similar groups, as classes, orders, families, genera,
species, races, even individuals, and the two sexes of a kind. This
accounts for the great variety of life. There is a great variety of
stages of evolution rather than a great variety of adaptation.

28 De Vries, Hugo, “The Evidence of Evolution,’ Science, N. S.,
Vol. XX, pp. 395-401, 1904.

°° Lankester, Prof. Ray, Address by, reported in the London Mail,
September, 1906.

°° Ammon O., “Der Abdnderungsspielraum,” Naturw. Wochen-
schr., Vol. XI, pp. 137-143, 149-155, 161-166, 1894.

*1 Bumpus, H. C., “The Variations and Mutations of the Intro-
duced Sparrow, Passer domesticus,’ in Biological Lectures, Wood’s
Holl Laboratory, 1897; also, ‘““The Elimination of the Unfit as illus-
trated by the Introduced Sparrow, Passer domesticus,” in Biological
Lectures, Wood’s Holl Laboratory, 1899; also, “The Variations and
Mutations of the Introduced Littorina,’ Zool. Bull., Vol. I, pp. 247-
259, 1808.

CHAPTERAY.

DARWINISM ATTACKED (CONTINUED): THE
THEORY OF NATURAL SELECTION (CON-
TINUED).

CERTAIN objections urged by various authors may be said
to concern themselves more with the character of the varia-

Objection based tions themselves and the possibilities of their
on the linear and 4 ccymulation by selection, than with the manner
quantitative and
non-qualitative of their occurrence. For example, de Vries *
npr hs denies the species-forming capacity of Dar-
tions. winian selection of Darwinian (fluctuating)
variation, on the ground that these variations are only
“linear,” and thus cannot afford a basis for the creation of
new forms. Already existing bodies, organs, and parts
can be enlarged or made smaller, made smoother or rougher,
made bluer or less blue, greener or less green, that is de-
veloped plus-ward or minus-ward, but by this nothing really
mew is created. But, declares de Vries, the differentiation
of organs consists, taken by and large, in the development
of actually new characteristics ; therefore in such material as
that presented by the linear variations of Darwin, selection
cannot have the necessary basis for this production of new
characteristics.

Gustav Wolff * reiterates the same objection in his declara-
tion that while the theory of natural selection may get on
decently well when modifications embodying only quan-
titative changes in parts or organs are concerned, it is com-
pletely at a loss to account for modifications or adaptations
requiring as basis qualitative changes. Even the warmest

DARWINISM ATTACKED. | 1

advocates of the selection theory have to admit, says Wolff,
that they face a serious matter here. Weismann’ is quoted
as follows: “Wenn man sich die Umwandlung deshalb in
grésseren Schritten und durch Variationen von qualitativer
Natur geschehend denkt, so wird man uber dieses Hindernis
nicht wegkommen. Ich glaube aber, dass man von den
Variationen grosseren Betrages, wie sie bei domestizierten
Tieren und Pflanzen nicht selten vorkommen, bei den Pro-
zessen der Artumwandlung, wie sie in der freien Natur vor
sich gehen, vollstandig abgesehen hat, dass Mer tiberhaupt
nicht qualitative sondern nur quantitative Unterschiede der
Individuen das Material der Naturztchtung bilden, solche
aber sind immer vorhanden.” Wolff holds that there can
simply be no doubt that if natural selection can do any
modifying at all it has at most to limit itself solely to work
possible on a basis of quantitative variation of already ex-
isting structures.

Variation also of whatever kind is subject to Galton’s * law
of regression. This is, put briefly, that the young of

Galton'’s law Parents varying from the mean of their species
of regression. or race tend to vary also in the same direction
but less so than the parent, so that the mean or mode among
the young is nearer the species or race type (mean or mode)
than the parental type was. Or as Morgan’ has stated it:
“The facts of observation show that when a new variety ap-
pears its descendants are more likely, on the average, to
produce proportionately more individuals that show the same
variation, and some even that may go still farther in the
same direction. If these latter are chosen to be the parents
of the next generation, then once more the offspring may
show the same advance; but little by little the advance slows
down, until before long it may cease altogether. Unless,
then, a new kind of variation appears, or a new standard of
variation develops of a different kind, the result of selection
of fluctuating variations has reached its limit. Our experi-

72 DARWINISM TO-DAY.

ence seems, therefore, to teach us that selection of fluctuating
variations leads us to only a certain point, and then stops in
this direction. We get no evidence from the facts in favour
of the view that the process, if carried on for a long time,
could ever produce such great changes, or the kind of
changes, as those seen in wild animals and plants.”

There is something inherent in the make-up of the organ-
ism and something inevitably in incident to the phenomena of
variation which prohibit, even in ‘the most favourable cases,
the indefinite movement of variation. Johannsen,’ pro-
fessor of plant physiology in the University of Copenhagen,
finds that beans bred in pure lines, 7. e., not crossed, conform
perfectly with Galton’s law of regression. And Johannsen
holds that this regression must be a serious brake on the
species-modifying, 7. e., species-forming, activity of natural
selection. That is, while the species mode can be moved in
one direction or another by pure line breeding it can be so
moved only very slowly. And this same law of regression
will tend to break up a “mixed population” resulting from
crossed and miscellaneous breeding into distinct pure lines;
that is, each independent form-type tends to be constant, not
constantly moving, 1. e., transforming. New types must
arise chiefly then through (a) the crossing of races or
species (= hybridisation) or (b) through mutations.

Delage ‘ in his criticism of selection makes the point that
because the causes of variation are more feeble than the

Delage's eriti- CAUSES of fixity (as evidenced by the massing of
cism of Delbeuf’s variations around and close to the mean or mode,
mm and their increasing scarcity as they recede in
any direction from the mode (species type) ), the species
tends always to stand still rather than to change. If in the
first generation a thousandth of the individuals vary in the
same way, in the second generation only 1-1000 of the
thousandth part will show the same variation, reasons
Delage. But, as pointed out in chapter vi (“Darwinism De-

DARWINISM ATTACKED. 73

fended”’), this criticism was long ago met by Delbceuf, who
claimed to show mathematically that, however feeble may be
the number of varying individuals compared with those
non-varying, the number of the varying will always be
increasing and will finish by being greater than that of the
individuals holding to the type. Delage holds “Delbceuf’s
law” to be false as regards its attempted general applica-
tion to the selection of variation, conceding it to hold true
only in the hypothetical case where a persistent active modi-
fying cause influences for some reason but a part of the
individuals of a species. And Delage cannot conceive of a
cause endowed with such an attribute.

An objection that has been often made to the natural
selection theory may be put in the following general form:

It may be granted that selection can make evolu-

Selection may ., 4 ’ .
produce evolution tion, 7. ¢., adaptive change or progress, but this
eee not Will be done in such a way as to leave a con-
specieg (discon- tinuous chain or series. How is the chain
tinuous series)» broken into species? Areall our species simply
the existent ends of series or chains? But we see many
chains or series of discontinuous but obviously connected
species. Natural selection can make evolution but not
species. Darwin himself couched this objection more con-
cisely as follows: “Why, if species have descended from
other species by fine gradations, do we not everywhere see
innumerable transitional forms? Why is not all nature in
confusion, instead of the species being, as we see them, well
defined ?”

Professor Morgan, in his “Evolution and Adaptation,”
discusses this objection in the following paragraphs (pp.
129-131):

“The answer that Darwin gives [to his own just quoted
query] is, that by competition the new form will crowd out
its own less-improved parent form, and other less-favoured
forms. But is this a sufficient or satisfactory answer? If

74 DARWINISM TO-DAY.

we recall what Darwin has said on the advantage that
those forms will have in which a great number of new
variations appear to fit them to the great diversity of
natural conditions, and if we recall the gradations that exist
in external conditions, I think we shall find that Darwin’s
reply fails to give a satisfactory answer to the question.

“Tt is well known, and Darwin himself has commented on
it, that the same species often remains constant under very
diverse external conditions, both inorganic and organic.
Hence I think the explanation fails, in so far as it 1s based
on the accumulation by selection of small individual varia-
tions that are supposed to give the individuals some slight
advantage under each set of external conditions. Darwin
admits that ‘this difficulty for a long time quite confounded
me. But I think it can be in large part explained.’ The
first explanation that is offered is that areas now continuous
may not have been so in the past. This may be true in
places, but the great continents have had continuous areas
for a long time, and Darwin frankly acknowledges that he
‘will pass over this way of explaining the difficulty.” The
second attempt is based on the supposed narrowness of the
area, where two species, descended from a common parent,
overlap. In this region the change is often very abrupt,
and Darwin adds:

“To those who look at climate and the physical condi-
tions of life as the all-important elements of distribution,
these facts ought to cause surprise, as climate and height
or depth graduate away insensibly. But when we bear in
mind that almost every species, even in its metropolis, would
increase immensely in numbers, were it not for other com-
peting species; that nearly all either prey on or serve as
prey for others; in short, that each organic being is either
directly or indirectly related in the most important manner
to other organic beings,—we see that the range of the in-
habitants of any country by no means exclusively depends

DARWINISM ATTACKED. 75

on insensibly changing physical conditions, but in a large
part on the presence of other species, on which it lives, or
by which it is destroyed, or with which it comes into com-
petition; and as these species are already defined objects,
not blending one into another by insensible gradations, the
range of any one species, depending as it does on the range
of others, will tend to be sharply defined.’

“Here we have a petitio principu. The sharp definition of
species, that we started out to account for, is explained by
the sharp definition of other species!

“A third part of the explanation is that, owing to the
relative fewness of individuals at the confines of the range
during the fluctuations of their enemies, or of their prey,
or in the nature of the seasons, they would be extremely
liable to utter extermination. If this were really the case,
then new species themselves which, on the theory, are at
first few in numbers ought to be exterminated. On the
whole, then, it does not appear that Darwin has been very
successful in his attempt to meet this objection to the
theory.”

A rather surprising objection is that of Pfeffer,’ who
contends that selection cannot be the cause of the formation

of species, for if it were real, however feeble

Pfeffer’s objec- . ‘ :

tion based on the its effects, it would transform species much
2 areal more rapidly than they are transformed; and in

order to transform a species in a long time the
protection afforded by the selection of small additions or
modifications is so feeble as to be illusory. And adequate
protection under such a system of species transformation
is imperative. This is a curious argument, for it has always
‘been one of the claims of the mutationists that a “hurry-
up” theory is needed in order to satisfy the familiar objec-
tion that the physicists’ estimate of the actual age of the
world is too low to admit of the production of the hosts of
kinds of animals and plants which we know to have existed

76 DARWINISM TO-DAY.

by the process of natural selection. But Pfeffer, who is
an ingenious debater, makes out a very plausible case for his
contention.

Of the many special questions that have been asked of the
selectionists two may be mentioned, simply as examples illus-
trative of a rather formidable category of objections most
of which are concerned with certain particular phases of
evolution or groups of evolution phenomena rather than
with the whole problem of species-forming. Many such
special objections or questions touching specific cases were
taken up and answered by Darwin in his “Origin of
Species.””. Morgan has recently (“Evolution and Adapta-
tion’) gone over critically many of these special objections
and Darwin’s answers to them, and pointed out clearly
that in numerous cases Darwin relied for his answers on
evolution factors which the neo-Darwinians have attempted
to read out of court. In many tight places Darwin availed
himself of the Lamarckian factor of the cumulation, through
inheritance, of the effects of use and disuse, or of other
functional stimuli originating either in internal or ex-
trinsic conditions. That is, Darwin, while constantly trying
to rely, and whenever possible relying on natural selection
as the species-forming and adaptation-explaining cause,
never hesitated, when it seemed necessary, to admit the
influence and effect of the inheritance of acquired characters
or the influence of other, to him, unknown factors. In
most cases of degeneration, for example, he adopted a
Lamarckian explanation.

The question of how sterility between species could have
arisen is a case in point. “That this property of species is

useful to them in the somewhat unusual sense
at ak that it keeps them from freely mingling with
species sterility other species is true,’ says Morgan; “but this
by selection. ; : ;

would be a rather peculiar kind of adaptation.
If, however, it be claimed that this property is useful to

DARWINISM ATTACKED. 77

species, as Darwin himself claims, then, as he also points out,
it is a useful acquirement that cannot have arisen through
natural selection. It is not difficult to show why this must
be so. If two varieties were to some extent at the start
less fertile, inter se, than with their own kind, the only way
in which they could become more infertile through selection
would be by selecting those individuals in each generation
that are still more infertile, but the forms of this sort would,
ex hypothese, become less numerous than the descendants
of each species itself, which would, therefore, supplant the
less fertile ones.” Darwin admits that this situation cannot
apparently be explained by natural selection, and simply
says that to him it appears “that the sterility both of first
crosses and of hybrids is simply incidental or dependent on
unknown differences in their reproductive systems.”

Wolff * has urged strongly the objection that natural selec-
tion does not explain the degeneration or atrophy of parts,

Objection that at least not large or nearly complete reduction.
selection cannot And Weismann and other selectionists long
eee ago conceded that some sort of auxiliary prin-
generationof ciple was necessary to explain degeneration on
Le a Darwinian basis. This principle was supplied
by Weismann, under the name of panmixia, which is, simply,
that a constantly active selection is necessary not only for
the evolutionary development or specialisation of an organ
but as well for its retention in specialised condition.”’ *’
So that an organ which is no longer used and is therefore
useless comes no longer under the supporting influence of
selection (on the basis of advantage) and must consequently
degenerate. But, as Wolff says, it seems obvious that such
an influence or effect of the cessation of selection or of
panmixia (so-called by Weismann because all variations
good and bad alike mix and compensate each other) can
at best lead to degeneration or atrophy only when the
negative or reducing variations are in the majority, for when

78 DARWINISM TO-DAY.

this is not the case the average of the survivors cannot
change. Weismann himself has in recent years recognised
the inadequacy of panmixia alone to explain degenerative
phenomena. He says:* ... “In most retrogressive pro-
cesses active selection in Darwin’s sense plays no part,
and advocates of the Lamarckian principle, as above re-
marked, have rightly denied that active selection, that is,
the selection of individuals possessing the useless organ in
its most reduced state, is sufficient to explain the process of
degeneration. I, for my part, have never assumed this,
and have on this very account enunciated the principle of
panmiria. Now, although this, as I have still no reason
for doubting, is a perfectly correct principle, which really
does have an essential and indispensable share in the process
of retrogression, still it is not alone sufficient for a full ex-
planation of the phenomena. My opponents, in advancing
this objection, were right, to the extent indicated, and as
I expressly acknowledge, although they were unable to
substitute anything positive in its stead or to render my
explanation complete. The very fact of the cessation of
control over the organ is sufficient to explain its degenera-
tion, that is, its deterioriation, the disharmony of its parts,
but not the fact which actually and always occurs where an
organ has become useless—viz., its gradual and unceasing
diminution continuing for thousands and thousands of years
and culminating in its final and absolute effacement.”

To supply the lack in the present neo-Darwinian explana-
tion of retrogression Weismann calls on his new theory of
germinal selection, the “rehabilitator of the natural selec-
tion theory” (for an account of this theory see chapter viii).
But Wolff and Morgan and others have shown how unsatis-
factory and inadequate this third attempt at an explanation
is, even if we grant the actuality of germinal selection, a
hypothesis which has by no means met with any general
acceptance by biologists.

DARWINISM ATTACKED. 79

In all our discussion of the effectiveness of the natural
selection theory one feature of it has so far not been ques-
tioned. And that is the actual selecting power when the
variations or differences among individuals are large enough
to be conceivably of real advantage or disadvantage to the
respective organisms. That is to say, we have not brought
into question the alleged rigour of the struggle for existence
upon which rigour depends, of course, the selection and the
survival of the fittest. The very phrases “struggle for ex-
istence” and “‘survival of the fittest” presuppose and assume
a rigour of competition and a life-and-death-determining
value of the variations or differences that are fundamental
features of the natural selection theory. Let us, however,
not hesitate to scrutinise these basic assumptions of the
Darwinians.

What of the actual rigour of the struggle that must be
presupposed in order to give small variations a life-and-

Eorutiny of the death-determining worth? Does it exist? Has
claimed extreme it been observed? Is the actual (admitted)
Se dali production of thousands or millions of eggs.
consequent per- or embryos in localities capable of supporting
aa but tens or hundreds of individuals, sufficient
reason for deducing an endless, searching, utterly rigorous
competition sufficient to give the slightest variations
a weight in the balances determining death or life?
In the first place, this tremendous competition must be
largely over, if it exists, before the individuals come to
maturity. Especially is this absolutely true of all species
that live for a long time in immature stages and a very short
time in the adult stage, as the Mayflies ** with only a night-
long adult life. Many insects of complete metamorphosis
(i. e., those whose adult stage, assumed during a quiescent
encased pupal stage, is very different from their larval
stage) which have very elaborate structural specialisations in
the adult stage have had their fate as offspring-producing

80 DARWINISM TO-DAY.

agents decided for them in immature, 7. e., egg, larval, or
pupal, life, and this immature life is in most cases by far
the larger part of the insect’s duration of existence.

Henslow ** sowed together the same quantity of two
kinds of wheat in a square yard of ground. The young
wheat plants that came up were many times as many as the
soil could support; the passive struggle for life was intense.
In the end twenty heads ripened and these were all of one
of the two kinds sown. The experiment was repeated in
the following year with the same result. In the struggle
one kind of wheat had a distinct advantage over the other.
But this selection depended wholly on special characters or
strength of the young stages. None of the adult characters
cut any figure in this selection, which was decided before
ever the plants came to maturity. And this is true, it seems
to me, of most of struggle and selection.

It is not in the adult state that the oppressive abundance
exists: in the forest to-day are about as many crows as last
year; in the meadows as many yellow butterflies as in sum-
mers by. The eggs and the young are the stages which
figure in mortality tables. They need the variations and
adaptations ; the pressure is largely gone before maturity is
reached. However, the adaptations of the fully-developed
body, in structure and function, certainly do not fall behind
those of the embryonic and immature stages. Indeed they
obviously are more complex and perfected. }

But after all what determines just what millions of trout’s

Indiscriminate CGZs Shall be destroyed and what thousands
death. shall hatch small fry? Many a sharp-eyed trout
fisherman, many a keen-witted nature observer, many a
trained biologist will answer: Chiefly chance, the luck of
position, the good fortune of not being devoured by the
roaming things that paddle or crawl in the upper reaches of
trout streams. What shall decide when the big whale opens
his mouth in the nudst of a shoal of myriads of tiny

DARWINISM ATTACKED. 81

Copepods floating in the pelagic waters of the Aleutian seas,
what Copepods shall disappear forever? Mainly, we may
say, the chance of position. A bit more or less of size, or
strength, or redness, or yellowness, or irritability or what
not of form and function is going to avail little when the
water rushes into the yawning throat. Now this chance
and this luck are the luck and chance of the law of prob-
abilities; that is, luck and chance capable of being mathe-
matically determined. Given so much ocean, with so many
whales swimming about in such and such curves at such and
such rates and opening and closing their mouths inter-
mittently at such and such intervals, and just so many
shoals of so many million Copepods, these shoals at such and
such distances apart, and any mathematical friend will
reckon for you the chances any one Copepod individual has
at any given moment of being swallowed. But Darwinian
variations in the Copepod body will be represented by no
function in the mathematician’s formula. When the scores
of little streams dry in California every summer, what deter-
mines whether millions of Californian water-insects of
scores of kinds shall die in July or not? Mainly life or
death is determined for them by their good or ill luck in
being in one of the few streams that do not dry up, or in
one of the many that do dry. Kelsey Creek runs into
Clear Lake, in northern California; it is usually ever-living,
but some summers it suddenly dries up. Fish play back and
forth between this stream and the lake; at the time of the
sudden drying a few hundreds of thousands out of many
hundreds of thousands that habitually live in the stream and
adjacent lake waters find themselves one awful day gasping
painfully for water to wet their drying gills. They gasp a
short while and then die. Did they all have the same num-
ber of scales, the same shape and size of body, the same
tinges of fleeting colour? No, they represented most of the
possible gamut of Darwinian variation for their particular

ae DARWINISM TO-DAY.

species. But they were dead all together, by the ill-chance
of position. In Lagunita, a small artificial lake on the
campus of Stanford University, water pours in from two or
three rivulets during the rainy season so as to fill it and
make it an abiding place for many aquatic organisms that
swim in or are washed in through the dikes. And thou-
sands of little fishes and water beetles and dragon-fly
nymphs and the like live contentedly there for seven or eight
months. But with the rainless summer months come swift
evaporation and steady leakage, and by September all the
thousands of little fishes and insects lie dying there together
in the last few puddles. It is the hard luck of a fatal chance
against which all the variations in colour, in size, in scales,
in spines, and what not are as one as far as helping or sav-
ing any of the gasping possessors is concerned.

One might go on tiresomely but one does not need to point
the moral of these tales. Wolff *’ has clearly fancied how
the fate of millions of tapeworms may hang on the recep-
tion in the German Reichstag of a clever speech for or
against meat laws. To go so far isn’t necessary: the very
life-history of the tapeworm and of hundreds of similarly-
lived vermian parasites shows to what nearly absolute de-
gree chance rules their fate, and how utterly insignificant
a part in it miscellaneous individual variation can possibly
play.

But aside from the part that what we may call fortune *°
of position plays in determining life or death among indi-
viduals, what of the actual rigour of the strug-
gle in those cases where death does not come
to thousands at a moment;—in the whale’s
mouth, by catastrophe of flood or drouth, or by the elephant’s
tread on the ant-hill? To this question of the rigour of
intra-specific struggle I have given some personal attention
in insect life, and while to detail observations here would
be impossible, I may say baldly that no such rigour of in-

How real is per-
sonal selection ?

DARWINISM ATTACKED. 83

dividual selection based on variation “* in colour, in pattern,
in venation and other wing characters, in hairs and in
numerous other structural characters, as demanded by the
needs of the selection theory, is to be detected. I find
just as much variation represented in series of mature
individuals collected miscellaneously after having lived for
more ‘or less time a free life exposed to all the dangers of
this life, exposed, that is, to the rigour of the individual:
struggle for existence, as among series of similar extent of
individuals of the same species collected just at the time of
reaching maturity but before enjoying any opportunity to
be weeded out (on a basis of disadvantageous variation)
by the rigour of the life-struggle. Just as many varying
individuals, with variations of just as much extent and va-
riety, were found in series exposed to the struggle, in which
these variations are presumably capable of saving or losing
life, as among series not yet exposed; in other words, just
as much variation exists after enduring the selective rigour
of the struggle as existed on the day when the insects are
hrst.exposed to it,

Conn ** expresses his belief concerning destruction by
chance and the rigour of the struggle as follows:

Conn’s discus: 4s eiscriminate destruction occurs con-
sionof the chances Stantly, and certainly influences the problem of
ae survival. Of the hundreds of individuals that
are produced where few can live, many are destroyed in-
discriminately, independent of the principle of survival of
the fittest, and of these that are thus killed doubtless some
are superior to those that survive. This principle of indis-
criminate elimination does not in the slightest deny the
force of the principle of survival of the fittest, but only indi-
cates that its action is not absolutely rigid. The fittest do
not always survive, for many of them are destroyed.

“On the other hand the least fit do not always perish.
Whether an individual shall live or die in the struggle is

34 DARWINISM TO-DAY.

largely a matter of accident. Many a well-equipped indi-
vidual will die, while many another, even though handi-
capped by decidedly unfavourable characters, will continue
to live and produce offspring because of some specially
favourable conditions. Nothing could seem to be more
decidedly disadvantageous than a broken leg, and, if the
principle of elimination of the unfit were rigid, broken-legged
individuals should be speedily destroyed. But it is quite
common to find animals with broken legs or arms which
yet succeed in living perfectly well. They have repaired
their broken members by processes of bone growth, and have
been able to carry on their part in the struggle for life and
survive competition. J have found a frog with the whole
of both feet bitten off, and yet with the wounds healed, the
animal living without feet, and hence hardly able to swim,
but side by side in competition with other well-developed
animals. JI have found a clam that in its young condition
had received a severe rent in one gill, through which, by
some twist the body had been thrust, giving rise to the
extraordinary condition of three gills on one side of the
body and one on the other, a truly monstrous abnormity.
But this clam had lived to maturity and produced eggs in
quantities equal to any other clam.

“Now such instances simply show the complexity of the
conditions which determine survival. They indicate that
these animals were favoured in some respects sufficiently to
counteract the disadvantage of their mutilations. But the
fact that so many instances are found does show that single
characters do not always determine survival or elimination.
The question whether an individual survive is dependent
upon many factors, of which utility of various organs may
be one and accident another. What would seem more sure
from a logical standpoint, than that, in the intense struggle
for life due to numerous individuals seeking for food, a
frog who was unable to swim because of the loss of his

DARWINISM ATTACKED. 85

feet would be sure to be a loser? Even if the inflammation
caused by the wound did not destroy him, it would seem
impossible for the animal to obtain his share of food. Of
course, a footless race would be eliminated in a compara-
tively short time, but the survival of so many mutilated
individuals shows that selection is not so rigid as to eliminate
all unfit individuals, even though their disadvantage be very
great.

“Tf a very disadvantageous character may thus fail to pro-
duce destruction it must be still more true that a favour-
able character, occurring in a single individual, has really
little chance for survival. The individual possessing it will
have to compete with accident, with indiscriminate slaughter,
and with other conditions which we have just seen may be
sufficient to preserve even a broken-legged individual.
Nothing can seem more evident than that the web of the
foot and the muscles of the legs are of use in swimming,
and have therefore been developed by the preserving influ-
ence of natural selection. If anything is of selective value,
these characters certainly are. But when we find that a
frog with no feet can survive the struggle for existence, it
is evidently difficult to believe that single variations, either of
use or disadvantage, will have any special likelihood of sur-
viving at the expense of other members of the race, so as
eventually to replace all others. But only thus can they
be ‘seized upon by natural selection and preserved.’ ”’

There are two important objections to the natural selec-
tion theory based on the relations of this theory with the

oo is other selection theories, namely sexual
tion needs the Selection and artificial selection. Wolff *’ has
leant , made the criticism that natural selection must
theory, which is be supported by the sexual selection theory
ache in order to stand. It makes no pretension of
explaining those extraordinary secondary sexual characters
such as ornamentation, songs, dances, odours, etc., which

86 DARWINISM TO-DAY.

not only are of no conceivable utility in the struggle for
existence but are in many cases of obvious disadvantage.
It relies wholly on sexual selection to explain them, and
yet in Wolff’s eyes, and indeed in the eyes of most biologists,
sexual selection is practically discredited. It certainly can-
not explain some or many of these characters. (See account
of the sexual selection theory and the criticisms of it in
the next chapter.) Therefore, say Wolff and other anti-
Darwinians, natural selection 1s undermined in just so far
as it relies on the sexual selection theory to sustain it.
The other objection is that the natural selection theory
rests altogether too largely on an unwarranted analogy with
Pine -
tion rests too = has graphicaily expressed the contrast between
largely on an .
analogy witharti- the facts and processes of the two kinds of
cial selection. selection in the following double-column table:

Natural selec: the phenomena of artiScial selection.

ARTIFICIAL SELECTION.

(1) rests on the wish (Willen)
and intelligence of the breeder,
except in a certain few cases of
“unintentional breeding’ (See
Darwin, ‘Origin of Species.’’)
(2) selects exceptional, most
widely divergent characters,
which appear only in a few
individuals.

(3) complete isolation (pure
breeding) of the selected indi-
viduals.

(4) often leads to exaggerated
development and to a sickly dis-
position, so that the whole con-
stitution suffers.

(5) leads comparatively rapidly
to new forms.

(6) The = artificially-produced

NATURAL SELECTION.

(1) rests on the unvolitional
and umnreasoning resultant of
natural forces.

(2) is a selection of slight dif-
ferences, appearing simultane-
ously in many individuals.

(3) pure breeding is often very
difficult through the possibility
of crossing with the parental
type.

(4) effects no injury to the
whole constitution, but on the
contrary a strengthening and
bettering of it.

(5) The modification of species
is effected, presumably almost
always, very slowly, for if it
were otherwise the appearance
of new species would be often
observed.

(6) The natural races (varie-

traces are unstable; they revert
easily to the ancestral type if
allowed to run wild; this is so
probably because of their recent
origin.

DARWINISM ATTACKED. 87

ties) are stable; they do not
revert if the outer conditions
(environment) remain constant;
this is so probably because they
are more firmly established by

reason of greater age.

(7) The = artificially-produced (7) Natural varieties do not
traces of the same species are cross in nature, either with
in most cases fertile among each other or with the ancestral
themselves. type.

The most important contrast between the two kinds of
selection lies, in my eyes at least, in the results obtained in
the character of the new forms. As Morgan** well says,
“we should not lose sight of the fact that even after the most
rigorous selective process has been brought to bear on
organisms, namely, by isolation under domestication, we do
not apparently find ourselves gradually approaching nearer
and nearer to the formation of new species, but we find, on
the contrary, that we have produced something quite differ-
ent. Inthe light of this truth, the relation between the two
selective theories may appear quite different from the inter-
pretation that Darwin gives of it. We may well doubt
whether nature does select so much better than does man,
and whether she has ever made new species in this way.”

De Vries expresses very positively his belief that no artifi-
cial races are fixed and constant forms, in the sense that
natural varieties are. And this difference he believes to rest
on the radically different method *’ of origin of the two
kinds of forms; the domestic ones through carefully main-
tained selection; the natural ones through definitive imme-
diately fixed and enduring mutations.

If one stops to recall his own familiar knowledge of the
cultivated plants ** and will roughly classify the cultivated
fruits and vegetables and ornamental plants with which he is
acquainted into two categories depending upon the mode of
reproduction, that is whether by division or by seeds, one
will be struck by the great preponderance of the first of the

88 ‘’ DARWINISM TO-DAY.

two categories,—the category, namely, of cultivated plant
races which are reproduced practically exclusively by
division (1. ¢., by cuttings, roots, scions, buds, etc.). The
reason for relying upon this kind of reproduction is, in
nearly every case, that these races do not breed true to seed,
i. e., the races are not fixed, are unstable. And even among
those races which we are accustomed to allow to reproduce
by seed how necessary it is to maintain the unusual environ-
ment, the exaggerated excellence of conditions of food
supply, humidity, protection from natural enemies, etc., if we
are to be successful in maintaining the parental characters of
the plant. Let a few individuals escape from the hothouse
or fertilised and sprinkled garden and see how soon, if they
can persist at all, they lose their characters of amelioration,
and become most pitifully unadorned.

In Pfeffer’s “* eyes the fundamental difference between
the two selection processes rests on the fact that the breeder
or plant ameliorator selects his individuals (the “to be
saved’’) on the basis of the character or condition of single
characteristics, while in nature survival is not determined
by such conditions, but on a basis of total or all-around fitness
or advantage. ‘‘The moment,” says Pfeffer, ‘that one be-
lieves one’s self to be able to place in parallel, simply and
directly and in general, the activity of the breeder and the
activity of the struggle for existence, and from this false
generalisation deductively to compare the selective work of
the breeder based on definitive special characters with the
automatic selective work of nature based on similar specific
characteristics, that moment one enters the camp of the
teleologists, whether he is doing it knowingly and will-
ingly, or not. In short it is a logical fallacy when one as-
sumes to substitute for the selective action of the breeder a
mechanically-working natural selection. Only in a single
kind of case has this position any justification, and this not
on account of logical correctness but on account of the pecu-

DARWINISM ATTACKED. 89

liar identity of the circumstances. And this is when a single
definitive characteristic is so all-important and dominant in
the life of a race or species that its presence really has a
life-and-death-determining value in the struggle for exist-
ence; in this case the killing out of all the individuals not
provided with this specific character has the same re-
sult as an actual selection of the possessors of this char-
acter. The farther, however, the actual circumstances differ
from this case, in so far as a number of characteristics, and
not a single one, determines the outcome of survival, by just
so much less can the Darwinian explanation be made to
cover the situation.”

De Vries sums up a full and careful discussion ** of

natural as compared with artificial selection as follows: “In
conclusion, summing up all our arguments we may state that
there is a broad analogy between breeding-selection in the
widest sense of the word, including variety-testing, race-
improvement, and the trial of the breeding ability on one
side, and natural selection on the other. This analogy, how-
ever, points to.the importance of the selection between ele-
mentary species,and the very subordinate roleof intra-specific
selection in nature. It strongly supports our view of the
origin of species by mutation instead of continuous selec-

tion. Or to put it in the terms chosen lately by Mr. Arthur

Harris in a friendly criticism of my views: ‘Natural selection
may explain the survival of the fittest, but it cannot explain
the arrival of the fittest.’ ”’

Finally I desire to add an objection that has real weight
with me, whatever may be the personal attitude of other

Anircreasing naturalists or students to it. And that is, that
number of work-

ing biologists 2 Constantly increasing number of working

unsatisfied with biologists find themselves, on a basis of their
the selection

theories. cumulative individual observation and experi-

ence and thought, unsatisfied with the explanation of adapta-
tion and species-forming offered by the selection theories.

go DARWINISM TO-DAY.

Men using, or rather, testing, these theories every day in
their work in field and laboratory, find selection insufficient
to explain the conditions that their observation and experi-
ments reveal to them. These men are students in all the
different lines of biological work; they are zoologists, bota-
nists, palzontologists; they are students of anatomy, physi-
ology, cecology, and taxomony (classification); they are
embryologists, pathologists, animal and plant breeders.
From all these lines of work come increasing complaints ;
selection cannot explain for me what I see to exist. From
some the cry is more bitter: selection is a delusion and false
guide; I reject it utterly. For me, I repeat, this is an
objection of much significance and importance. Just as
modern chemistry seems to be finding its long useful atoniic
theory now a restraint and a hindrance in understanding the
wonderful new facts that have followed the pushing out of
investigation into the rich fields of physical chemistry, so
the biological experimentalists, the students of variation and
heredity, of life mechanics, of physico-chemical biology,
are finding the rigid theory of selection’s control of all
processes and phenomena a rack on which they will no
longer be bound.
Coupled with the significance of this general objection to
the reign of the selection theory—a general objection that
___ the selectionists will say is simply the objection
The concessions ; ; : -
of the selection- that the selection theory is objected to—is the
sic added significance of the concessions in the way
of supporting theories that the neo-Darwinians have made
to the general increase and sharpness of scientific criticism
of selection ; conspicuous examples are Roux’s theory of the
battle of the parts, and Weismann’s theory of germinal
selection. This latter is no less than a neo-Darwinian ex-
planation of how determinate variation, that is ortho-
genesis, may be explained non-teleologically. Which is
practically to rob natural selection of all influence in the

DARWINISM ATTACKED. gi

primary determination of lines of descent. But to these
supporting and concessionary theories we shall come in
a later chapter.
To show how definitive and positive an anti-Darwinian
position is taken by some biologists I shall quote some para-

osineey's graphs from an interesting short paper by Kor-
radical anti-se- schinsky,*° a Russian botanist whose formula-
lection position, tion of the theory of species-forming by hetero-
genesis preceded that of de Vries by two years. In this
paper (which is a vorlaufige Mitteilung published in Ger-
man preliminary to the issuance, in the publications of the
Royal Academy of Sciences of St. Petersburg, of a larger,
more detailed paper) Korschinsky arranges in parallel
columns the various corresponding or contrasting items of
the selection theory compared with the heterogenesis theory
of the author himself (for this full table see chapter xi).
From this table I quote only the following statements to
show how differently from the Darwinian view the probable
effects of the struggle for existence may appear to another
naturalist and to what radically anti-Darwinian conclusions
a man may come who interprets the effects of selection in
this way:

“The origin of new forms can only occur under condi-
tions favourable for them, and the more favourable such
conditions are, that is, the less severe the struggle for ex-
istence is, the more energetic is their development. Under
severe external conditions new forms do not arise, or if they
appear they are extinguished.

“The struggle for existence, and the selection which goes
hand in hand with it, compose a factor which restricts new-
appearing forms and restrains wider variations, and which is
in no way favourable to the production of new forms. It
is indeed an inimical factor in evolution.

“Were there no struggle for existence, then there would
be no extinguishing of arising or already arisen forms. The

g2 DARWINISM TO-DAY.

organic world could then develop into a mighty tree, whose
branches could all remain in blooming condition, so that
the now isolated extremest species would be united with all
others through gradatory forms.

“The adaptation resulting from the effects of the struggle
for existence is absolutely not identical with advance, for
higher-standing, more complex forms are by no means
always better adapted to outer conditions than the lower
ones. The evolution [used here by the author as synony-
mous with advance or progressive complexity] of organisms
cannot be explained in a purely mechanical way. In order
to explain the origin of higher forms from lower it is neces-
sary to postulate in the organisms a special tendency to ad-
vance which is nearly related to or identical with the
tendency to vary, which tendency compels the organisms
to advance so far as the outer conditions permit.”

These declarations sound strange and perhaps almost
absurd in the ears of one accustomed for years to
hear only the Darwinian interpretation of the effects of the
strugele for existence and natural selection. But taken
up one by one, as they are by Korschinsky, and developed
and explained, they begin to have a kind of plausibility,
an appeal to our reason, of much that sort which the Dar-
winian interpretation has and makes. After all the Darwin-
lan interpretation is proved only in so far as it possesses a
high degree of plausibility and makes a convincing appeal
to our reason. Of exact proof, in the nature of observed
fact or result of experiment, or of mathematical demonstra-
tion, there is little in the case either of the Darwinian or
the Korschinskian interpretation.

Those other biologists “" who, like Korschinsky, take the
extreme and positive stand that the struggle and selection
are not factors in evolution, or if factors are really hinder-
ing and opposing ones, constitute, however, by far the
smaller body in the ranks of the anti-Darwinian critics when

DARWINISM ATTACKED. 93

compared with those whose arraignment of selection is
chiefly a protest against its assumption of altogether an
undue share of influence in species-forming, and whose
principal attempt is to reduce selection to a secondary place
among evolutionary factors, giving first place to that influ-
ence or those influences which determine the character and
direction of variation. Still the totally anti-Darwinian
critics are not few, and are not without ingenuity and
capacity in debate.
But better justified by what we know to-day and far saner
in their estimate of the Darwinian factors are such critics
_ as Delage and Morgan. “The conclusion of
Dirty lial this criticism,” says Dglage,”* at the end of a
detailed critical discussion of the “true role of
selection,” “is that selection is powerless to form Species.
Its role, however, is not nul, but it is limited to the sup-
pression of variations radically bad, and to the maintaining
of the species in its normal character. Far from being an
instrument for the evolution of species it guarantees their
fixity.” And elsewhere he says: “Species come from fixed
variations. The formation of species is due ordinarily to
general variation [a conception of change much like that of
de Vries’s mutations and sudden fixed origin of elementary
species], very rarely to strong individual variation [sports or
discontinuous variations], and never to weak individual
variation [fluctuating or Darwinian variation].
Morgan * in a recent popular essay in which he takes a
strong stand against natural selection as a species-forming
Morgan's ad- factor and in favour of “definite variations”
verse criticism of (de Vriesian mutations) concludes as follows:
the species-form- ,,
ing value ofse- | 1” the preceding pages I have tried to bring
lection: into contrast the point of view of the
Darwinian school and the newer conception of the sur-
vival of elementary species. I have tried to show what
selection has meant to the selectionists. They have

79 1662

94 DARWINISM TO-DAY.

never hesitated to take each particular character of an
animal or plant, and dress it up in more perfect gar-
ments, while the body of the species, if I may so speak,
has been left as it was before. There has been a con-
tinual tampering with the characters of the organism with
the laudable intention of doing with them that which na-
ture herself seems unable to do, namely, to dissociate them
from the rest of the organisation and perfect them in this
way or in that. It is this meddling with the fluctuating
characters of the species that has been the characteristic
procedure of the Darwinians, in their attempt to show how
new species have been created. In contrast to this method,
the theory of the survival of species assumes that a form
once made does not have its individual parts later disso-
ciated and adjusted to better fit the external needs of the
species. Such a new form can change only by becoming
again a new species with a new combination of characters;
some of which may be more developed in one direction than
before, others less, etc.

“New forms on the Darwinian theory are supposed to be
created by a process of picking out of individual differences.
If, in addition to this, Darwin supposed that at times varie-
ties and species crowd each other out nothing new is thereby
created.* On the other hand the theory of the survival of
definite variations refers the creation of new forms to an-

*“Tf the survival of certain species determines, in a metaphorical
sense, the kinds of future mutations that occur, the course of evo-
lution may appear to be guided by selection or survival; but, how-
ever true it may be that selection acts by lopping off certain
branches, and limits to this extent the kinds of possible future muta-
tions, the origin of the new forms remains still a different question
from the question of the survival of certain species. This negative
action of selection is not the process that most Darwinians have
had in mind as the source of the origin of new species. It is true
that Weismann believes that selection of individual differences deter-
mines the origin of new species. and that the creation of these new

species determines the future course of variations in the same direc-
tion, but his argument that fluctuating variations can go on indefi-

DARWINISM ATTACKED. 95:

other process, namely, to a sudden change in the character
of the germ. The creating has already taken place before
the question of the survival of the new form comes up.
After the new form has appeared the question of its per-
sistence will depend on whether it can get a foothold. The
result is now the same as when species crowd each other
out. This distinction appears to me to be not a matter of
secondary interest, but one of fundamental importance, for
it involves the whole question of the ‘origin of species.’ So
far as a phrase may sum up the difference, it appears that
new species are born; they are not made by Darwinian
methods, and the theory of natural selection has nothing to
do with the origin of species, but with the survival of already
formed species. Not selection of the fittest individuals, but
the survival of the sufficiently fit species.

“There is a fundamental difference between the idea that
fluctuating variations become specific characters through
accumulation by selection, and the idea that new species
arise as definite variations, which, with their appearance,
characterise the new form as a new species. According
to the Darwinian theory, natural selection performs a double
duty, first, to build up new species, and second, to maintain
them in competition with other species. According to the
other view, species are not formed by any kind of selection,
and the question of survival only concerns the maintenance
of species already formed. The primary problem is the
problem of the ‘origin of species.’ The central idea is not

nitely varying in the direction of selection is refuted by what has.
been actually found to be the case when the process of selection of
fluctuating variations is carried out. Most of the individuals of a
species may be brought in this way to show the particular character
selected in its highest degree as a fluctuating variation, but it appears:
not possible to transgress this limit; and rigorous selection in every
generation is necessary to hold the individuals to the highest point.
reached. Only by the appearance of new definite variations can a
given character be permanently fixed, or a new species created that.
will show fluctuating variations around the new standard.

96 DARWINISM TO-DAY.

what species survive, but how species originate; no matter
whether they are going to become victorious or not.

“After a species has appeared it will surely be admitted by
every one, that forms that can survive will survive! If
Darwin’s theory meant only this to those who adopted it,
is it not surprising that such a truism should have been
hailed as a great discovery? Was not the theory heralded
because it seemed to explain how new species arose? What
shall we say then when we find a situation like that existing
at the present time, when we are told that after all the only
difference between Darwin’s theory of natural selection and
the theory of the survival of definite variations is that in the
one case fluctuating variations are selected, and in the other
mutations, and that in both cases natural selection is the
key to the evolutionary process! Is not the ‘origin of
species’ still the real point at issue?

“T yield to no one in admiration for what Darwin has done
in behalf of the biological sciences, for he succeeded, where
the great French zoologists failed, in establishing the prin-
ciple of evolution. Furthermore no other hypothesis, that
has as yet been proposed, accounts so well for the wide-
spread occurrence of adaptation of organisms to the environ-
ment as does the principle of natural selection. But appre-
ciation of Darwin’s claims in these directions need not blind
us to the insufficiency of the theory of natural selection to
account for the origin of species; nor to the fact that his
followers have been especially concerned in propounding
and making application of this side of the theory. They
have shown little interest in selection as the great conserv-
ing factor of evolution, and the reason for this is not far
to seek, because of the much greater importance that they
have attributed to natural selection as a creative factor in
building up individual differences into specific characters.”

DARWINISM ATTACKED. 97

APPENDIX.

* De Vries, H., ‘Die Mutationstheorie,” Vol. I, pp. 83 ff., 1901.

* Wolff, Gustav, “Der gegenwartige Stand des Darwinismus,” p.
9, 1896.

* Weismann, A., ‘““Aufsatze tiber Vererbung,” p. 116, 1892.

* Galton, Francis, ‘‘Natural Inheritance.” I quote from Galton as
follows: :

“As soon as the character of the problem of filial descent had
become well understood, it was seen that a general equation of

Galton’s state- the same form as that by which it was expressed,
mentofthelaw also expressed the connection between kinsmen in
of regression. == every degree. The unexpected law of universal re-
gression became a theoretical necessity, and on appealing to facts,
its existence was found to be conspicuous. If the word ‘‘peculiarity”
be used to signify the difference between the amount of any faculty
possessed by a man and the average of that possessed by the popu-
lation at large, then the law of regression may be described as
follows: Every peculiarity in a man is shared by his kinsmen, but
on the average in a less degree. It is reduced to a definite fraction
of its amount quite independently of what its amount might be.
The fraction differs in different orders of kin, becoming smaller
as they are more remote. When the kinship is so distant that
its effects are not worth taking into account, the peculiarity of the
man, however remarkable it may have been, is reduced to zero in
his kinsmen. This apparent paradox is fundamentally due to the
greater frequency of mediocre deviations than of extreme ones,
occurring between limits separated by equal widths” (pp. 194-195).

“The law of regression in respect to stature may be phrased
as follows: namely, that the deviation of the sons from P are on
the average equal to one-third of the deviation of parent from P,
and in the same direction or more briefly still; if P + (+D) be
the stature of a parent, the stature of the offspring will on the
average be P + (+1-3 D)” (p. 104).

“Thus, however paradoxical it may appear at first sight, it is
theoretically a necessary fact, and one that is clearly confirmed
by observation, that the stature of the adult offspring must, on the
whole, be more mediocre than the stature of their parents; that is
to say, more near to the M of the general population” (p. 95).

“The law of regression tells heavily against the full hereditary
transmission of any gift. Only a few of many children would
be likely to differ from mediocrity so widely as their mid-parent,
and still fewer would differ as widely as the more exceptional of

98 DARWINISM TO-DAY.

the two parents. The more bountifully the parent is gifted by
Nature, the more rare will be his good fortune if he begets a son
who is as richly endowed as himself, and still more so if he has
a son who is endowed yet more largely” (p. 106).

° Morgan, T. H., “Evolution and Adaptation,” p. 104, 1903.

* Johannsen, W., “Uber Erblichkeit in Populationen und in reinen
Linien,” 1903.

” Delage, Yves, “L’Hérédité,” 2d ed., p. 398, 1903.

® Pfeffer, G., “Die Umwandlung der Arten,” p. 26, 1894.

* Wolff, G., ‘“Beitrage zur Kritik der Darwin’schen Lehre,” pp. 50
ff. I quote as follows:

“Fir jeden, der sich den Grundgedanken der Selektionstheorie
auch nur einigermassen klar gemacht hat, kann kein Zweifel daru-
Wolff's criticism ber bestehen, dass die nattrliche Selektion immer
of panmixia. nur ein einziges Anpassungsgebilde, niemals aber
zwei oder gar noch mehr zu gleicher Zeit ztichten kann. Es konnen
z. B. Auge und Ohr nicht gleichzeitig geztichtet werden, denn sonst
miissten ja die ausgelesenen Individuen mit den besten Augen
zugleich auch diejenigen mit den besten Ohren sein, eine Vorausset-
zung, die wir um so weniger machen durfen, als dieselbe ja auf
alle ubrigen Organe ausgedehnt werden musste. Die Naturzuchtung
wird sich immer auf die Ziuchtung desjenigen Organes verlegen,
dessen bessere Ausbildung fur das Tier den grosseren Vorteil
bietet.. Ist ein gutes Auge niitzlicher, als ein gutes Ohr, so
sind die Individuen mit den besten Augen denen mit den besten
Ohren gegenuber in Vorteil: sie werden gezitichtet. Wahrend also
das Auge geztuchtet wird, steht das Ohr nicht unter dem Einfluss
der Selektion, also unter dem Einfluss der Panmixie. Unter diesem
Einflusse stehen aber samtliche Organe mit Ausnahme des ein-
zigen, welches gerade geziichtet wird, sie fangen daher alle an,
einen Ruckbildungsprozess einzugehen. Sobald nun eines der nicht
gezuchteten Organe bereits so weit rtickgebildet ist, dass der Zu-
stand desselben eine Gefahr fur den Organismus in sich schliesst,
alsdann wird sich die Naturztichtung diesem Organe zuwenden,
denn dann ist eine bessere Ausbildung dieses Organes ein grosserer
Vorteil als die des andern. Die Selektion iiberlasst also dieses
letztere seinem Schicksal, d. h. der riickbildenden Panmixie, unter
deren Einflusse die andern Organe immer noch stehen.

* Jedes Gebilde, welches durch Naturztichtung hervorgebracht ist,
auch wenn es jetzt von untergeordneter Bedeutung ist, muss einmil
Generationen hindurch, d. h. so lange als die Selektion zu seiner
Herstellung brauchte, das allerwichtigste gewesen sein, eine Konse-
hae die allein gentigt, den ganzen Darwinismus ad absurdum zu
uhren.

DARWINISM ATTACKED. 99

“Wem die Absurditat dieser ganz unvermeidlichen Konsequenzen
noch nicht einleuchtet, der mdge sich die Sache an einem Bilde
versinnlichen. Wenn ein Lehrer eine Klasse von Schilern zu
unterrichten hat und dabei so verfahrt, dass er immer einen Schiler
zu sich auf sein Zimmer nimmt und dort unterrichtet, unterdessen
aber die tbrigen treiben lasst, was sie wollen, so wird er bei einer
Inspizierung durch den Schulrat mit seiner Klasse wenig Staat
machen konnen, weil die Schtiler weit mehr Zeit auf das Vergessen,
als auf das Behalten und Lernen verwendet haben. Sie werden
daher nicht nur das, was sie bei diesem Lehrer in den wenigen
Einzellektionen, sondern auch das, was sie in den friithern Klassen
gelernt hatten, vergessen haben. Genau so beim Organismus. Alle
Organe stehen eine weit langere Zeit unter dem Einflusse der Pan-
mixie, als unter dem der Selektion; wenn also die Panmixie einen
Einfluss ausubt, so wird dieser Einfluss der titberwiegende sein, und
wenn dieser Einfluss dem der Selektion entgegengesetzt ist, so wird
der Einfluss der Selektion ganzlich aufgehoben werden, d. h. der
ruckbildende Einfluss wtirde die Oberhand behalten, das ganze
Tier musste sich mit Stumpf und Stiel—zuriickbilden, ein Vorgang,
bei welchem die Panmixie zu vergleichen ware einem Feuer, das
ein Dorf ergriffen hat, die Selektion dagegen einer Feuerwehr,
welche mit der Spritze immer wieder an dasjenige Haus fahrt, aus
dem gerade die starksten Flammen herausschlagen. Diese Feuer-
wehr wird gewiss nicht viel von dem Dorfe retten.

“Der Darwinismus muss also, wenn er der Absurditat dieser
Konsequenzen entgehen will, notwendig annehmen, dass diejenigen
Organe, welche jeweilig nicht unter dem Einflusse der Selek-
tion stehen, ruhig und unbeschadet warten k6nnen, bis die miitter-
liche Sorgfalt der Selektion, welche sich immer nur einem ihrer
Kinder widmen kann, sich ihrer wieder annimmt. Das heisst der
Darwinismus muss annehmen, dass die Panmixie keinen Einfluss
auf die Organisation hat.

“Da aber die Variierung eine Thatsache ist, so muss er anneh-
men, dass gunstige und ungiinstige Variierung die gleiche * Wahr-
scheinlichkeit haben, womit ein weiterer Beweis geliefert ist, dass
der Darwinismus nur mit graduellen Veranderungen rechnen kann.

“Die Lehre von der Panmixie und die Selektionstheorie vertragen
sich nicht mit einander. Aus der Richtigkeit der einen folgt die
Falschheit der andern. Und insofern die Selektionstheorie eigentlich
die Voraussetzung zur Lehre von der Panmixie ist, vernichtet diese
letztere sich selbst durch ihre blosse Existenz. Ihre Bejahung

*Ist man, wie Emery, der Ansicht, dass ungiinstige Variierungen

grossere Wahrscheinlichkeit haben als giinstige, so muss man
hieraus allein die Unrichtigkeit der Selektionstheorie folgern.

100 DARWINISM TO-DAY.

schliesst ihre Verneinung in sich, d. h. sie leidet an einem unl6sbaren
inneren Widerspruch.”

*°? This necessity of constantly active selection must apply as well
to specialised function as to specialised organ. But it is not diffi-
Example of inef- cult to call attention to certain functions or physio-
fective panmixia. logical capacities of various animals which seem to
negative this deciaration of the need of constant selection to main-
tain specialisation. For example, I have shown (‘‘Regeneration in
Larval Legs of Silkworms,” Jour. Exper. Zool., Vol. I, pp. 593-599,
Io figs., 1904) that the long ‘‘domesticated” mulberry silkworm larva
possesses the capacity of regenerating any of its legs, if the mutila-
tion has not removed the whole appendage. Now the assumption
of most selectionists is that this capacity for regenerating injured
legs and other parts is a specialisation, adaptive and advantageous.
But in connection with this particular case, it should be borne in
mind that the silkworm has been for approximately 5,000 years a
domesticated animal, cared for under such conditions as to make
the natural loss of legs almost an impossible occurrence. Perfectly
protected against such natural enemies as bite off legs, there has
certainly been nothing of that sharp necessity, during all the life of
countless generations of silkworms, which is supposed to be the
basis for maintaining the advantageous capacity for regeneration.
There has been a clear field for panmixia. But the regenerative
capacity still exists in effective degree.

11 See a recent paper by Vejdovsky (“Uber einige Stisswasser-
Amphipoden, III. Die Augenredtiktion bei einem neuen Gam-

Example of pro- mariden aus Irland und uber Niphargus caspary
eh rae Pratz aus den Brunnen von Munchen,” in S. B. Kgl.
cable by sie ln Bohm. Ges. d. Wiss., 1905), embodying the results of
selection. his studies on the reduction of the size in certain
small Crustaceans (Gammaridz), which he found living in the Irish
Sea at a depth of from 130 to 150 feet. These Crustaceans form
an interesting series showing a gradual reduction of the eyes. It is
shown clearly that this reduction proceeds very regularly from the
periphery toward the interior. First, there is apparent a high degree
of variability of all parts, then the optic parts of the eye disappear,
and finally the nervous, or retinal, parts. This course of reduction
is only explicable, according to the author, on a basis of the
inherited degenerative results of a lack of use, for in any decreas-
ing use exactly this course of individual degeneration of the eye
is what is met with; that is, the active external optic elements
degenerate first, and later the nervous, or retinal, elements.

** Weismann, A., “On Germinal Selection as a Source of Definite
Variation,” trans. McCormack, pp. 38 ff., 1896.

DARWINISM ATTACKED. IO

*® The Mayflies, or lake-flies, constitute an order (Ephemerida)
of insects which spend from several months to perhaps a couple
of years in their immature life (as crawling, gill-bearing, wingless
aquatic larve), and from a few hours to at most a few days as
free-flying adult creatures. Many other insects (indeed most in-
sects) have a much shorter adult life than immature life, and
most of them have very different structures in the two life-periods.
Hundreds of insect kinds take no food in the adult stage and many
others that do have food-habits quite different from the larval habits.

** Henslow, G. W., “Origin of Flowering Structures,” 1895.

*® Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” pp. 41,.
ff., 1898. I quote as follows:

“Ware die Wahrscheinlichkeit einer niitzlichen Variierung wirk-
lich so klein, wie Emery behauptet, ware sie wirklich so klein, wie

Wolff's discus- die Wahrscheinlichkeit, dass in dem Satz einer
sion of the selec- Druckseite durch beliebiges Ersetzen eines beliebigen.
tion coefficient. Biuchstaben durch einen beliebigen andern ein Druck-
fehler verbessert wird, dann k6nnte sich der Darwinismus gleich
von vornherein begraben lassen. Er konnte dann nicht mehr sagen:
die Auslese des Bessern muss notwendig eine Steigerung des.
Niitzlichen ergeben. Die erforderlichen Voraussetzungen waren dann
noch viel verwickelter; es mtisste dann auch noch tuber den Inten-
sitatsgrad’* des Selektionsprozesses eine Voraussetzung gemacht
werden: er muss so hoch sein, dass die Summe aller ttberlebenden
+ dx?” (unter denen vor Eintritt des Selektionsprozesses die unge-
heure Mehrzahl negativ, das Vorhandensein positiver dagegen
ausserst unwahrscheinlich war) eine positive Zahl wird. Der
Kampf ums Dasein an und fir sich niitzt also noch gar nichts;
erst wenn er jenen ganz bestimmten Intensitatsgrad erreicht, dann
erst wirkt die Selektion verbessernd. Und wie hoch ist dieser von

* Dieser Intensitatsgrad ist eine genau bestimmte, wenn auch
selten bestimmbare Zahl. Sie giebt das Verhaltnis der erzeugten zu
den sich fortpflanzenden Nachkommen an. Man konnte diese
Verhaltniszahl den Selektionskoeffizienten nennen.

Ich muss trotz der Einwendungen Emerys meine Schreibweise
dx beibehalten. Sage ich, dass der Darwinismus mit dem Vari-
ierungsinkrement nur dann rechnen diirfe, wenn er von ihm keine
bestimmte Grosse voraussetzt, sondern ihm gestattet, sich der Null
beliebig zu nahern, und will ich dies durch ein mathematisches
Zeichen ausdriicken, so ist das einzig richtige dx. Ob die wirk-
lichen Variierungsinkremente messbar sind oder nicht, ist dabei
ganz gleichgiltig. Ubrigens ist Emery im Irrtum, wenn er meint,
alle seien messbar. Die wenigsten sind es. Die Differenz in der
Disposition zur Tuberkulose zwischen zwei vollig gesunden Indi-
viduen ist z. B. gewiss nicht messbar, und doch kann gerade hier

eine, wenn auch noch so kleine Differenz, im Kampf ums Dasein
den Ausschlag geben.

102 DARWINISM TO-DAY.

Emery geforderte Intensitatsgrad! Nimmt man an, ein Tier habe
40,000 Millionen Kinder, von welchen nur 2 Individuen sich fort-
pflanzen, so ware nach Emerys Rechnung dieser Selektionsprozess
noch nicht einmal intensiv genug, um es wahrscheinlich werden zu
lassen, dass diese 2 im Durchschnitt sich irgendwie verbessert
haben.* Und dabei ist noch vorausgesetzt, dass die Selektion von
den 40,000 Millionen wirklich ganz genau die 2 Besten heraus-
gefunden hat. Dies wird nattrlich nie der Fall sein. Denn je
geringer die Prozentzah! der gtinstigen Variierungen ist, um so
weniger wird das Resultat der Selektion von Variierungsvorteilen,
um so mehr dagegen von Situationsvorteilen abhangen. Nehmen
wir z. B. eine Tierklasse, bei welcher die Verhaltniszahl der erzeug-
ten und der erhaltungsfahigen Individuen der von Emery geforderten
Zahl vielleicht am nachsten kommt: die Bandwiirmer. Nehmen
wir also an, ein Bandwurm erzeuge wahrend seines ganzen Lebens
40.000 Millionen Eier. Unter den abgehenden Eiern findet eine
Selektion statt: nur die, welche vom Zwischenwirt gefressen werden
konnen sich zur Finne entwickeln. Es werden aber ungeheuer
wenige gefressen, die meisten gehen ungefressen zu Grunde. Wir
haben also eine intensive Selektion. Wovon hangt es aber ab, ob
das Ei gefressen wird? Ganz ausschliesslich von aussern Umstan-
den. Die individuellen Eigenschaften der Eier kommen nicht in
Betracht. Wir haben also hier einen Selektionsprozess, bei
welchem ein Einfluss der Variierungsvorteile absolut ausge-
schaltet ist, bei welchem ausschliesslich Situationsvorteile in Be-
tracht kommen. Nur in Bezug auf die Resistenzfahigkeit konnten
Variierungsvorteile von Belang sein, die wir aber ausschalten
konnen, indem wir uns auf ein bestimmtes Anpassungsgebilde
beschranken (was ttberhaupt bei jeder Darwinistischen Betrachtung
notig ist), z. B. die Entstehung der Saugnapfe, etc. Dass unter
den relativ wenigen gefressenen Eiern sich eines von den 2 mit
einer in Bezug auf die Saugnapfe vorteilhaften Keimesanlage
befinde, ist ausserst unwahrscheinlich. Die gefressenen Embryonen
kommen nun ‘zur engeren Wahl.’ Nicht alle werden in fremden
Organismus bleiben. Viele werden einfach abgehen. Bei diesem
Selektionsprozess, der lange nicht so intensiv ist, als der erste,

1 Wobei noch zu beachten ist, dass die Zahl 100 der Elemente, in
welche Emery ein Organ sich aufgelost denkt, selbstverstandlich
eine willktrliche ist, und dass diese Zahl der Wirklichkeit naturlich
um so naher kommen wird, je grosser sie angenommen wird. Wie
enorm wiirde sich dann erst die Zahl der Kombinationen vermehren!
Ubrigens kommt es auf die Zahlen gar nicht an: das Wichtige ist,
dass mit der Emeryschen Annahme der Hypothesenkomplex,
welchen die Selektionstheorie darstellt, um eine neue und zwar das
Fundament betreffende Hypothese vermehrt wurde.

DARWINISM ATTACKED. 103

konnen auch (aber keineswegs ausschliesslich) Variierungsvorteile
mitwirken. Die soweit gelangten Finnen kommen nun zu einer
noch engern Wahl. Nur diejenigen entwickeln sich weiter, deren
Zwischenwirte gefressen oder gegessen werden. Diesen Selektions-
prozess konnen wieder eine Unzahl der verschiedensten Faktoren
beeinflussen. Mehr oder weniger grosser Geschmack an rohem
Fleisch, mehr oder weniger grosse Achtsamkeit der Sanitatsbehor-
den, diplomatischer Notenwechsel tber Grenzverkehr: das sind alles
Faktoren, die in Betracht kommen konnen. Eine schneidige Reichs-
tagsrede kann unter Umstanden uber Tod und Leben von Tau-
senden von Bandwiirmern entscheiden. Eine Klasse von Faktoren
kommt aber ganz gewiss nicht in Betracht, das sind individuelle
Vorteile der Finnen. Auch hier ist also die Wirkung der Vari-.
ierungsvorteile ausgeschaltet. Unter den gefressenen oder geges-
senen Finnen findet wahrscheinlich wiederum ein Selektionsprozess
statt, bei welchem Variierungsvorteile (aber keineswegs ausschliess-
lich) mitwirken k6nnen. Von den 2 Individuen mit vorteilhaft
variierten Saugnapfen wird aber aller Wahrscheinlichkeit nach kein
einziges zur letzten Wahl gekommen sein. Also selbst bei denjeni-
gen Tieren, bei welchen die Uberproduktion die grosste ist, konnte
nach der Emeryschen Rechnung die Selektionstheorie zur Erkla-
rung der Anpassungserscheinungen nicht mehr verwendet werden.”

*® See Piepers, M. C., “Mimikry, Selektion, Darwinismus,” 1903,
pp. 376 ff. Author shows how an enormous mortality among
oysters can occur without any reference to their fitness for lite,
and also gives other interesting cases of indiscriminate non-
selective mortality.

™ Kellogg and Bell, “Studies of Variation in Insects,’ Proc.
Wash Acad. Sci., Vol. VI, pp. 203-332, 1904. I quote the follow-
ing: |

“There are certainly few selectionists left who honestly believe
that the minute fluctuating variations in pattern, in size, in curve

Example of non- of a vein, in length of a hair, etc., have that life-
selection of trivial and-death value which is the sole sort of value that
differences. an ‘advantageous variation’ must have to be a ser-
viceable handle for the action of natural selection. As a matter
of fact, no systematist will have escaped having had it distinctly
-impressed on him that he recognises differences in the pattern of
lady-bird beetles, in the number of fin rays in fishes, in the branch-
ing of a vein in flies’ wings, that no enemy, no agent of natural
selection, can recognise, at least to the extent of pronouncing
sentence of death (or not pronouncing it) on its basis. And
further, no biologist really satisfies himself with the worn state-
ment, ‘We must not presume to judge the value of these trivial,

104 DARWINISM TO-DAY.

these microscopic differences, for we do not know all the complex
interrelation and interaction of the organism and its environment.’
We do not, but we do know for many cases that such differences
are actually not of life-and-death selective value, and reason
compels us to believe to a moral certainty that in other cases these
fortuitous trivialities have similar lack of life-and-death importance.
The case of the variation of the convergent lady-bird beetle, Hip-
podamia convergens (p. 275 et seq.), is distinctly in point. In our
account of this variation we have called attention to the suggestive-
ness, in its light on the rigour of the ‘struggle for existence’ among
individuals, of the fact that armong several thousand individuals,
gathered together to hibernate after an active life, having been
exposed to the attacks of bird and insect enemies, to the rigours
of climatic conditions and to the necessities of obtaining food
(other smaller insects, as aphids, etc., caught alive), such a range
of variation in pattern is found as enables us to describe (so that
they may be actually readily distinguished by verbal description),
eighty-four ‘aberrations’ or pattern-variates; lady-birds with no
spots, with one, with two, with three, with each of all the numbers
up to and including eighteen distinct small black spots, the different
numbers usually being represented by several different combinations
of spots. Systematic entomologists describe Hippodamia convergens
as a brown-red beetle with six black spots on each elytron, and this
description is true for most beetles of this species. But not at all
for all; nor even approximately for many. After a season of ex-
posure to the struggle for existence, to the rigours of selection,
individuals with one spot, with six spots, with twelve spots, with
eighteen, find themselves alive and healthy; they come together
to pass a quiet winter under the fallen oak leaves on a mountain
side, ready to mate miscellaneously in the spring, and produce young
of all manner of pattern (as far as number and arrangement of
spots go); which young, whether twelve-spotted as they ought to
be, or no-spotted, or eighteen-spotted as they may be, will appa-
rently go safely through life despite the malevolent search of the
all-powerful Inquisitor, Rigour of Selection!

“Directly touching this point, too, are our data of the variation
of series of honey-bees collected from free-flying individuals after
exposure as adults to the rigours of outdoor life, as compared with
the variation in the series of bees, adult, but collected just as issu-
ing from the cells before being exposed as adults in any way to
the external dangers of living. Series of both drones and workers
representing both exposed and unexposed individuals were studied.
The results of this examination are, put in one statement, that the
variation among the exposed individuals is no less than that among

DARWINISM ATTACKED. 105

the unexposed individuals. This means that these various, mostly
slight, blastogenic variations (although in such important organs
as the wings) which occur among bees at the time of their issuance
as active, winged creatures, are not of sufficient advantage or dis-
advantage to the individuals to lead to a weeding out (by death)
or saving of such varying individuals by immediate selective action.
Whatever the rigour and danger of the outdoor bee life, these
variations seem to be insufficient to cut any figure in the persist-
ence or non-persistence of any individual in the face of this rigour.”

** Conn, H. W., “The Method of Evolution,” pp. 72 ff., 1900.

7° Wolff, G., ‘“Beitrage zur Kritik der Darwin’schen Lehre,” pp.
24 et seq., 1808.

2° Plate, L., “Uber die Bedeutung des Darwin’schen Selections-
prinzip,” pp. 17-18, 1903.

2+ Morgan, T. H., ‘Evolution and Adaptation,” 1903.

2 De Vries, in a recent paper (‘“Altere und Neuere Selektions-
methode,” Biol. Centralbl., Vol. XXVI, pp. 385-395, 1906), describes
the new methods of plant amelioration adopted by the Svalfor Ver-
suchsstation (Sweden). These methods have been determined
largely by the acceptance of De Vries’s mutations theory as a
working hypothesis.

7? For account of the breeding and amelioration (artificial selec-
tion) of plants see Darwin, ‘Variation of Animals and Plants

Dee cenccn to. Undet Domestication,” many editions; Bailey, L.
books and papers i, “‘Plant-breeding,” 4th ed., 1900 ; Hays, W. M.,
on plant-breed- ‘‘Plant-breeding,” Bull. 29, Div. Veg. Phys. and
me Path, U. S. Dept. Agric., 1901; Webber, H. J.,
and Bessey, E. A., “Progress of Plant-breeding in the United
States,” Yearbook of U. S. Dept. Agric., for 18809, pp. 465-490;
Kellogg, V. L., “The Scientific Aspects of Luther Burbank’s Work,”
Pop. Sci. Mo., pp. 363-374, Oct., 1906 (reprinted in Appendix to
chapter ix of this book).

** Pfeffer, Georg, ‘“‘Die Umwandlung der Arten,” pp. 19-20, 1894.

25 De Vries, H., “Species and Varieties, their Origin by Mutation,”
pp. 798-826, 1905.

*° Korschinsky, S., ‘“Heterogenesis und Evolution,” Naturwiss,
Wochenschrift, Vol. XIV, p. 276, 1899.

?™ Coe, C. G., ‘‘Nature versus Natural Selection,” 1894. A book
devoted wholly to denying any validity at all to natural selection.

78 Delage, Yves, “L’Hérédité,” 2d ed,, p. 419, p. 843, 1903.

*° Morgan, T. H., ‘‘The Origin of Species through Selection Con-
trasted with their Origin through the Appearance of Definite
Variations,’ Pop. Sci. Mo., pp. 54-65, May, 1905.

CHAP ER yy.

DARWINISM ATTACKED (CONTINUED): THE
THEORY OF SEXUAL SELECTION.

THE differences between male and female individuals of
a single species are often striking; recall the gorgeous
colouring, the plumes and tufts and tail-feathers

Secondary s ,
sexual difer- Of many male birds compared with the sober
cy and quiet plumage of their mates; the antlers

of the stag, the mane of the lion and bison, the beard of
the goat, many monkeys, and of man. Recall the mamme
of the female quadrupeds, the brood pouches of the female
kangaroos and opossums, the small size, compared with their
mates, of many female birds, the winglessness of many fe-
male insects. Other less familiar kinds of animals show
sexual dimorphism or dichromatism in even more striking
degree, while in many others the differences are less con-
spicuous but nevertheless perfectly obvious if some attention
is given to looking for them. These differences in size,
colour, general appearances, and various specific structural
details in head, trunk, wings, feet, plumage, etc., are over
and beyond those primary radical differences existing in all
species in which the two sexes are differentiated. Some of
these differences may, however, have obvious relation to
the primary differences, in that they may be connected im-
mediately with the act of pairing or with the work of rear-
ing the young. The presence in male insects of complexly
developed holding organs, and in female mammals of milk
glands exemplifies differences of this category. A great many
sexual differences, however, have no such obvious direct
relation to the function of producing and rearing the young.
106

DARWINISM ATTACKED. 107

Such are the metallic purple and bronze colours of the male
grackles compared with the dull brown of the females; the
long tails and brilliant coloration of the male pheasants,
the great, spreading, patterned tail of the peacock, the
larger size or the winglessness of many female insects, etc.
All these differences between male and female of the same
species of animal, beyond or in addition to the differences
between the actual primary reproductive organs, are known
as secondary sexual differences, or the characters themselves,
which may be characteristics of physiology and habit as
well as the more familiar ones of structure, are called sec-
ondary sexual characters. The layman may not readily
appreciate the abundance and the great variety of these char-
acters, but it is a fact that almost all species of animals,
excepting those in the lower invertebrate branches, show
them, and if one will try to recall the aspect of the two
sexes in one after another of the species of animals with
which one is familiar, mammals, birds, insects, etc., one will
begin to realise how widespread and significant are these
secondary sexual characters.

Various biologists have made up classifications, from
various points of view, of the different kinds of these char-

Classifications 2cters; one classification, like that of Kramer ’
of secondary sex- for the secondary sexual characters of insects,
ual characters. ray be based on the different parts of the body
showing the differences between male and female indi-
viduals, as head, antenne, thorax, wings, legs, abdomen,
etc., and on the character of the differences themselves, as
whether differences in structure or in colour and pattern.
Another type of classification, and one more useful for our
present discussion, is that based on the apparent significance
or actual use of the differing characters. An excellent
classification of this type is that of Plate.* The following
are the principal subdivisions of this classification with a
few examples illustrating each:

108 DARWINISM TO-DAY.
CLASSIFICATION OF THE EXTERNAL SECONDARY SEXUAL CHARACTERS.

Group A. Characters which are useful to the possessor, or to its
young, or have an indirect relation to reproduction.

Sub-group 1. Specialisations in organs which aid in the finding of
individuals of the other sex. Examples, the extra-develop-
ment of the antenne in many male moths and beetles, the
enlarged and divided eyes of certain flies and May-flies, the
enlarged tactile feelers of male Daphnias, the larger or better
wings of many male insects, the swimming membrane, in the
breeding season, on the hind-legs of Molge paradoxa.

Sub-group 2. Specialisations that aid in mating. Examples, the
clasping organs of many male crabs, the hectocotylus of
octopuses, the expanded tarsi of many male insects, and in
general, the accessory copulatory organs of innumerable vari-
ous animal species.

Sub-group 3. Special size and form of the female due to the extra-
development of the ovaries. Examples, in Psychid moths and
parasitic Crustaceans.

Sub-group 4. Differences connected with care of the young. Ex-
amples, mammz of female mammals, brood-pouch of mar-
suplals, brood-sacs of male sea-horses, and brood-cavities in
the back of male Pipa (a frog).

Sub-group 5. Specialisations for defence or offence. Examples,
protective coloration of female birds and insects, mimicry
by female butterflies, antlers of the stag, strong canines of
many male mammals (wild boars, etc.), sting of the female
honey-bee, spurs of the cock, greater size and strength of
many male mammals and birds.

Sub-group 6. Differences in coloration which aid in the recogni-
tion of the sexes (“recognition marks” of Wallace).

Sub-group 7. Differences connected with various special habits of
life. Examples, the pollen-baskets of the worker honey-bees,
the winglessness of male fig-caprifying insects (Blastophaga),
the large differences between males and females of certain
insects where one sex lives parasitically, the other independ-
ently, as the scale insects, the Strepsiptera, etc., the beak
differences in the New Zealand bird, Heteralocha acutiros-
tris, whose male chisels out the hard wood with a short,
broad beak, while the female extracts insect larve from decay-
ing wood by means of a long, curved beak.

Group B. Exciting organs. These are found almost exclusively in
the males only, and serve to indicate the sexual excitement
of their possessors, and at the same time to stimulate or excite

DARWINISM ATTACKED. 109

the females. The excitation of the male is manifest to the
female through her senses of sight, hearing, and smell (in each
case through one or more of these), and this perception gives
rise reflexively to an excitation on the part of the female.

Sub-group 1. The male characters may appeal to the sense of sight
of the female: (a) by colours, as in the breeding plumage, or
coloration, of many birds, fishes, amphibians, and reptiles, or,
as in the constant brilliancy of colour and pattern in many
butterflies, other insects, and spiders; or (b) by striking form,
as the beard and hairy tufts of many monkeys and the
extraordinary “horns” and processes of certain lamellicorn
beetles ; or (c) by movable processes (often strongly coloured),
as the wattles and movable feathers (tail, etc.) of certain birds,
swelling cheek or neck sacs of turkeys, etc.; or (d) by strik-
ing movements, as the dancing on the ground or tumbling
and whirling in flight of certain birds, the mating-time bat-
tles of mammals, birds, and fishes, and the “love-dances” of
spiders.

Sub-group 2. The male characters appeal to the sense of hearing
of the females, as the song of birds, the cries and calls of
many mammals, frogs, and insects.

Sub-group 3. The male characters appeal to the sense of smell of
the females, as the odours given off by goats, chamois, musk-
deer, beaver, etc., and from the scent-scales (androconia) of
many male butterflies.

Group C. Reciprocal organs; that is, organs which exist in func-
tional condition in one sex but are inherited by the other only
in rudimentary and often non-functional form.

Examples; the reduced mammz of male mammals, the brood
pouch of the male Thylacinus; wingless female butterflies often
have a rudimentary sucking proboscis, which in some cases is in-
herited by the males without any reduction of the wings; in
cases of mimicry by female butterflies, the males often show
some traces of the changed colour-pattern; traces of spurs in
female pheasants, reduced horns of female antelopes and goats,
small “horns” on female lamellicorn beetles, undeveloped stridu-
lating apparatus in female crickets, katydids, etc.

Group D. Indifferent characters, without any apparent utility.

Sub-group 1. Rudimentary organs, which are wholly non-func-
tional in one sex, although still functional in the other.
Examples, the reduced wings of many female insects, the
rudimentary alimentary canal of male Rotatoria.

Sub-group 2. Negative characters, that is, those wholly failing in
one sex, although present in the other. This lack can be a

110 DARWINISM TO-DAY.

primary one, that is, indicate an older phyletic condition, as
the absence of antlers in the female deer; or be a secondary
one, that is, gradually acquired by progressive reduction, as
the loss of wings by many female insects.

Sub-group 3. Atavistic characters, as the more marked hairiness
on the breast of men as compared with women.

Sub-group 4. Correlated characters, which may be called into ex-
istence by other organs present; with the female mollusc
Anodonta, the shell is more strongly bowed in adaptive
correlation with the expanded brood chamber between the
gills.

Sub-group 5. A large number of secondary sexual characters
which are incapable of specific classification, as the minute
differences between the sexes in size and habitus; slight dif-
ferences in wing form in humming-birds, dragon-flies, and
butterflies; small differences in character and number of
tarsal and antennal segments of many insects.

As Plate justly remarks the foregoing classification can,
of course, make no pretension to completeness. But it

jeer indicates sufficiently clearly certain important
nificance of tke differences among the secondary sexual char-
pac acters; differences especially important in con-
nection with any attempt to get at an explanation of the
why and how of these characters. Such a classification
shows that many of these characters have uses which are
of a kind directly helpful in the struggle for existence, as the
strong antlers of the stags, useful in defence against attacking
enemies; the brood sacs of the kangaroos and opossum, use-
ful in caring for their helpless young; the milk-glands and
teats of all female mammals, the pollen-baskets and wax-
glands of the honey-bee which make the workers more
effective food-gatherers and food-storers, and the protective
colours and patterns of many insects and birds. But others,
many others, indeed, of these secondary sexual characters,
are either of a kind apparently useless in the struggle for
life, or even of a kind actually harmful. Of apparent useless-
ness are the reduced wings of some male insects, and the
host of slight differences in coloration, pattern, size, or

DARWINISM ATTACKED. 11!

shape, of different body-parts or of the whole body, the
beards and hair-tufts of many male mammals and the combs
and wattles of male gallinaceous birds. Of apparent harm-
fulness are those ultra-developed pro-thoracic and head
processes, “horns,” of stag and other lamellicorn beetles, the
conspicuous staring colours of many male birds, the long
dangling plumes, the weighty crests, and heavy dragging
tails of others, all these parts also usually being dangerously
conspicuously coloured. The lively loud song of many
male birds, and the dancing and leaping of numerous male
spiders and some male birds must also involve some danger
to the performers by attracting the attention of their enemies.
In fact most of those secondary sexual characters that are
classified under the general head of “exciting organs” are
apparently of a sort that should be actually disadvantageous
in the struggle for existence. They are of a character tend-
ing to make their possessors conspicuous and thus readily
perceived by their carnivorous enemies. How 1s to be
explained the existence of so many and such highly de-
veloped structural and physiological characters of this kind,
a condition that seems to stand in direct opposition to the
theory of natural selection? Darwin’s answer to this ques-
tion is contained in his theory of sexual selection.
This theory, in few words, is that there is practically a
competition or struggle for mating, and that those males are
Bee ine. successful in this struggle which are the stron-
ory ofsexual gest and best equipped for battle among them-
spies selves, or which are most acceptable, by reason
of ornament or other attractiveness, to the females. In the
former case mating with a certain female depends upon
overcoming in fight the other suitors, the female being the
passive reward of the victor; in the second case the female
is presumed to exercise a choice, this choice depending upon
the attractiveness of the male (due to colour, pattern, plumes,
processes, odour, song, etc.). The actual fighting among

112 DARWINISM TO-DAY.

males and the winning of the females by the victor, are ob-
served facts in the life of numerous animal species. But a
special sexual selection theory is hardly necessary to explain
the development of the fighting equipment, antlers, spurs,
claws, etc. This fighting array of the male is simply a special
phase of the already recognised intra-specific struggle; it is
not a fight for room or food, but for the chance to mate.
But this chance often depends on the issue of a life-and-
death struggle. Natural selection would thus account for
the development of the weapons for this struggle.

For the development, however, of such secondary sexual
characters as ornament, whether of special plumage, colour,
pattern, or processes, and song, and special odours, and
“love-dancing,”’ the natural selection theory can in no way
account; the theory of sexual selection was the logical and
necessary auxiliary theory, and when first proposed by
Darwin met with quick and wide acceptance. Wallace in
particular took up the theory and applied it to explain many
cases of remarkable plumage and pattern development
among birds. Later as he analysed more carefully his cases,
and those proposed by others, he became doubtful, and
finally wholly sceptical * of the theory.

The theory as proposed by Darwin was based on the fol-
lowing general assumptions, for the proof of each of which a

Pursiniad few to many facts were adduced. First, many
bases of the secondary sexual characters are not explicable
gah by natural selection; they are not useful in the
struggle for life. Second, the males seek the females for
the sake of pairing. Third, the males are more abundant
than the females. Fourth, in many cases there is a struggle
among the males for the possession of the females. Fifth,
in many other cases the females choose, in general, those
males specially distinguished by more brilliant colours, more
conspicuous ornaments, or other attractive characters.
Sixth, many males sing, or dance, or otherwise draw to

DARWINISM ATTACKED. 113

themselves the attention of the females, Seventh, the sec-
ondary sexual characters are especially variable. Darwin
believed that he had observed certain other conditions to ex-
ist which helped make the sexual selection theory probable,
but the conditions noted are sufficient if they truly exist.
Exposed to careful scrutiny and criticism—an admira-_
ble and convincing example of such scientific and impar-
tial criticism is Kramer’s analysis of the
Scrutiny and
criticism of the Secondary sexual characters of European in-
as sects—the theory of sexual selection has been
relieved of all necessity of explaining any but two categories
of secondary sexual characters, namely the special weapons
borne by males, and the special ornaments and excitatory
organs of the males and females. For examination has
disclosed the fact that males are not alone ° in the possession
of special characters of attraction or excitation. Regarding
these two categories Plate,’ in his able recent defence of
Darwinism, says, “the first part of this theory, the origin of
the special defensive and offensive weapons of males through
sexual selection is nearly universally accepted. The second
part of the theory, the origin of exciting organs has given
rise to much controversy. Undoubtedly the presumption
that the females compare the males and then choose only
those which have the most attractive colours, the finest song,
or the most agreeable odour, presents great difficulties, but
it is doubtful if it is possible to replace this explanation
by a better.” Some of these difficulties may be briefly
enumerated.
The theory can be applied only to species in which the
males are markedly more numerous than the femaies, or in
ene which the males are polygamous. In other
morenumerous cases there will be a female for each male
Sohreenae whether he be ornamented or not; and the
unornamented males can leave as many progeny
as the ornamented ones, which would prevent any cumula-

114 DARWINISM TO-DAY.

tion of ornamental variations by selection. As a matter of
fact-in a majority of animal species, at least among the
vertebrates, males and females exist in approximately equal
numbers.

Observation shows that in most species the female is
wholly passive in the matter of pairing, accepting the first

Female is usy- Male that offers. Note the cock and hens in
ally passive. the barnyard. 3

Ornamental colours are as often a characteristic of males
of kinds of animals in which there is no real pairing, as

ieiacie ces POMS those which pair. How explain by
cur on males that Sexual selection the remarkable colours in the
tall Jeo breeding season of many fishes, in which the
female never, perhaps, even sees the male which fertilises
her dropped eggs?

Choice on a basis of ornament and attractiveness implies
a high degree of esthetic development on the part of the

females of animals for whose development in
Assumption of er :
esthetic develop- this line we have no (other) proof. Indeed this
ment inlower choice demands esthetic recognition among
animals, : : pad
animals to which we distinctly deny such a

development, as the butterflies and other insects in which
secondary sexual characters of colour, etc., are abundant
and conspicuous. Similarly with practically all invertebrate
animals. Further, in those groups of higher animals where
esthetic choice may be presumed possible we have repeated
evidence that preferences vary with individuals. Certainly
they do with man, the animal species in which such prefer-
ences certainly and most conspicuously exist. In some
human races hair on the face is thought beautiful; in others,
ugly. Besides even if we may attribute fairly a certain
amount of zsthetic feeling to such animals as mammals and
birds, is this feeling to be so keen as to lead the female
to make choice among only slightly differing patterns of
songs? Yet this assumption is necessary if the development

DARWINISM ATTACKED, 115

of ornament and other attracting and exciting organs is to
be explained by the selection and gradual cumulation through
generations of slight fortuitously appearing fluctuating
variations in the males.

There are actually very few recorded cases where the
observer believes that he has noted an actual choice by a

Pos spaced. Lemale. Darwin records eight cases among
cases of choice birds. Since Darwin not more than half a
br emele dozen other cases, all doubtful, have been
recorded. Also a few instances, all more illustrative of
sexual excitation of females resulting from the perception
of odour or actions, than any degree of choice by females,
have been listed.

In numerous cases the so-called attractive characters of
the males, described usually from preserved (museum)

specimens, have been found, in actual life, to
Some so-called
attractive char- be Of such a character that they cannot be noted
acters not visible hy the female. For example, the brilliant
1n nature. :
colours and the curious horns of the males

of the dung beetles are, in life, always so obscured by dirt
and filth that there can be no question of display to the
female eyes about them. The dancing swarms of many
kinds of insects are found to be composed of males alone
with no females near enough to see; it is no case of an
excitatory flitting and whirling of many males before the
eyes of the impressionable females. Of many male katy-
dids singing in the shrubbery will not for any female that
particular song be the loudest and the most convincing that
proceeds from the nearest male, not the most expert or the
strongest stridulator? Similarly with the flitting male fire-
flies; will not the strongest gleam be, for any female, that
from the male which happens to fly nearest her, and not
from the distant male with ever so much better, stronger
light?

Stolzmann finds it difficult to understand, when nearly

116 DARWINISM TO-DAY.

related species differ widely in their ornamental plumage,
that this should be attributed to a difference in
Problem of preference among the females of the related
the Andean ; : : :
humming-birds, Species. The humming-bird, Schistes perso-
natus, lives in Ecuador on the west side of the
Andes, in a restricted range of four degrees of latitude. It
is distinguished from the nearly related Schistes geoffroy
especially in the possession by its male of a brilliant spot over
each eye. Schistes geoffroyi lives on the east side of the
Andes from Colombia to Central Peru, with a range cover-
ing over twenty degrees of latitude, which range is divided
into two completely separated regions by the Maranon
valley. Now if isolation alone is sufficient to produce a
change in the taste of the females, one would expect to find
two sorts of males (as far as ornamental pattern goes) in-
side this one species. But there is but one kind of male
through the whole range. Why is the taste of the female
constant through twenty degrees of latitude, while it is
changed on the other side of the Andes in a limited range
of four degrees of latitude? Another case presented by
Stolzmann is even more striking. The Chilian hummer,
Eustephanus galeritus, which is green in both sexes, has
migrated from the continent to the Juan Fernandez Islands.
On Masatierra Island it has changed to Eust. fernandensis,
in Masafuera Island to Eust. leyboldi. These two species
agree in the females with the original continental form
(that is, are green) while the males have become red, but in
different pattern in the two species. Eust. galeritus (the
Continental form) also occurs on Masatierra Island, in the
same form as on the continent, that is, with green male.
Now one must presume from this state of affairs that this
species (galeritus) has been able to reach Masatierra twice,
once long ago—the descendants of the invasion having
changed to Eust. fernandensis—and once more recently—
the descendants of these later migrants showing as yet no

DARWINISM ATTACKED. 117

sign of a transformation of the malecolour. Shall one in this
case and others like it, asks Stolzmann, assume a change of
beauty-ideal on the part of the females? Much simpler and
much more reasonable, according to Stolzmann, is it to see in
the change of colour of the males of the earlier migrants the
results of the direct influence of the new environment; the
islands are distinctly milder and warmer than the continent.

Even if the females do choose among the males on a basis
of attractiveness, how are the characters of the more at-

tractive males to become especially fostered

How are more ,
attractive char- amd accumulated by selection? Do such males
acters to be produce more offspring or more vigorous ones
fostered ? ; /

than the other males, which, though rejected
by the first females, find their mates among the females not
already mated? Are we to attribute to the more ornamental
males a particular vigour? If so, may not that very vigour
be the cause of the extra-production of colour or plumage
or wattles, etc.?

Darwin admits, in order to explain the beginnings of
colour and ornament development, a certain degree of differ-

_ | ence between the male and female in regard to

Darwin's sig- é f : :
nifcantadmis- their reaction to environmental influences. If
ut so, may not these admitted differences be really
sufficient to account for even a pretty high degree of differ-
ence in development of secondary sexual characters?

The special display of colours, tufts, plumes, spreading
tails, and other secondary sexual characters by the males at
mating time is an observed fact; the “dances”
of cranes and storks, the serenades of the song-
birds, the evolutions of the male spiders are all
familiar phenomena in the mating season of these animals.
And they probably do exercise an exciting effect on the
females, and are probably actually displayed for this pur-
pose. But does this in any way prove, or even give basis
for a reasonable presumption for belief in a discriminating

Does display
prove choice ?

118 DARWINISM TO-DAY.

and definitive choice among the males on the part of the
female? And it is this actual choosing which is the neces-
sary basis for the theory of sexual selection.

How explain the well-known cases of a similar extra-
development of plumage in the nuptial season by both

Bow éxplald males and females, as in certain herons and
ornamentsin other birds? And what of those other cases in
females or : — : f
common to both Which it is the female that is the brighter-cq-
sexes 7 oured individual of the pair? To explain the lat-
ter case Darwin assumes that in these cases the males have
done the selecting, but even this rather too easy reversal of
the situation postulated as a fundamental generalisation
of the theory does not explain the first of the questions in
this paragraph. Do both sexes among the herons do
selecting?

Morgan‘ lists twenty objections to the sexual selection
theory, several of which are identical with those already

mentioned in the foregoing paragraphs, but
Pevionites among which are several to which we have not
referred. One of these is that “some of the

objections that apply to the theory of natural selection
apply also with equal force to the theory of sexual selection
in so far as the results in both cases are supposed to be the
outcome of the selection of individual, or fluctuating, varia-
tions. If these variations appear in only a few individuals,
their perpetuation is not possible, since they will soon dis-
appear through crossing. It would be, of course, preposter-
ous to suppose that at any one time only those few indi-
viduals pair and leave descendants that have secondary
sexual characters developed to the highest point, but if
something of this sort does not occur, the extreme of
fluctuating variations cannot be maintained. Even if half
of the individuals are selected in each generation, the ac-
cumulation of a variation in a given direction could not go
very far. The assumption, however, that only half of all

DARWINISM ATTACKED. 11g

the individuals that reach maturity breed, and that all of
these are chosen on account of the special development of
their secondary sexual characters, seems _ preposterous.
Furthermore, if it is assumed that the high development of
the new character appears in a large number of individuals,
then it is not improbable that its continued appearance might
be accounted for without bringing in, at all, the hypothesis
of sexual selection.”

Again, Morgan well points out that “the development, or
the presence, of the esthetic feeling in the selecting sex is not
accounted for on the theory. There is just as much need to
explain why the females are gifted with an appreciation of the
beautiful as why the beautiful colours develop in the males.
Shall we assume that still another process of selection is go-
ing on, as a result of which those females are selected by the
males that appreciate their unusual beauty, or that those
females whose taste has soared a little higher than that of the
average (a variation of this sort having appeared) select
males to correspond, and thus the two continue heaping
up the ornaments on one side and the appreciation of these
ornaments on the others No doubt an interesting fiction
could be built up along these lines, but would any one be-
lieve it, and if he did, could he prove it?

“Darwin assumes that the appreciation on the part of
the female is always present, and he thus simplifies, in
appearance, the problem, but he leaves half of it un-
explained.

“There is another side to the question,” also says Morgan,
“the importance of which is so great, that it is surprising
that Darwin has not taken any notice of it. If, in order to
bring about, or even maintain, the results of sexual selection,
such a tremendous elimination of individuals must take
place, it is surprising that natural selection would not
counteract this by destroying those species in which a
process, so useless for the welfare of the species, is going

120 DARWINISM TO-DAY.

on. It is curious that this has not been realised by those
who believe in both of these two hypotheses.

“What has just been said applies also with almost equal
force to the development of such structures as the horns
of the deer, bison, antelopes, and the brilliant colours of
many insects and birds. If in nature, competition between
species takes place on the scale that the Darwinian theory
of natural selection postulates, such forms, if they are much
exposed, would be needlessly reduced in numbers in the
process of acquiring these structures. So many individuals
would have been at such a disadvantage in breeding, that
if competition is as severe as the theory of natural selection
postulates, these species could hardly be expected to compete
successfully with other species in which sexual selection was
not taking place.”

Finally to make an end of miscellaneous objections and
come to that one which promises to be, if it is not already,

. the most serious obstacle in the way of the
Experimental ; eae
evidence is op- | S€Xual selection theory, it is a fact that all the
posed tosextal evidence (though it be little as yet) based on
selection theory. ; ;
actual experiment is strongly opposed to the
validity of the assumption that the females make a choice
among males based on the presence in the males of ornament
or attractive colours, pattern, or special structures. I may
mention especially the striking experiments of Mayer ‘
(which, published in a small entomological journal of
limited circulation, have not received the attention that they
deserve) on the large Bombycine moth, Callosamia pro-
methea. This well-known American moth expands about
three and one-half inches and shows unusually pronounced
secondary sexual differences as to colour and pattern. The
females are reddish-brown in ground colour, while the males
are blackish and in the two sexes the pattern is distinctly
different. If there is any moth species in which the colours
and general pattern of the male ought to be readily obvious

1. Fe

DARWINISM ATTACKED. “yer

to the female, and in which sexual selection might be pre-
sumed to have been the influence in producing a pronounced

aa male type 40! preferred pattern, it As this
perimentson Species. Mayer’s simple and convincing ex-
PIERCE: periments were as follows: Mayer took four
hundred and forty-nine pupz (in cocoons) of the moth
Callosamia promethea, which had been collected in Massa-
chusetts and New Jersey, south to Loggerhead Key in the
Dry Tortugas Islands off Florida. This island is separated
by many miles of ocean from other land, and is hundreds
of miles south of the range of the species. Evidently no
interference with Mayer’s experiments could come from
outside individuals of this species. The moths issued during
May and June in the proportion of about two males for
each female. The males of this species seek out the female
for pairing and can do this for a considerable distance. As
many as several dozen males will find a single female and
hover, fluttering, about her. Mayer’s first experiments were
directed to the end of determining if the males found the
females by sight or by smell. By enclosing females in
numerous jars variously arranged and covered or uncovered,
it was readily determinable that males never pay any
attention to females enclosed in transparent jars so closed
as to prevent the escape of any odours from the female,
while to females enclosed in boxes or wrapped in cotton so
as to be invisible but yet capable of giving odour off into
the air males came promptly and hovered about. To locate
the organs of scent in the female Mayer cut off abdomens
from various females and then placed abdomens and ab-
domenless females at some little distance apart. Males
came to the abdomens and not to the thorax plus wings,
legs, and head parts. Females were proved to increase in
attractive power with age, and virgins are a little, but only
a little, more attractive than already fertilised females. It
was readily proved, by experiments with males whose an-

122 DARWINISM TO-DAY.

tennz were covered with shellac, photographic paste, glue,
paraffin, etc., that the sense of smell is seated in the antennz.
Males with antenne covered with photographic paste did
not find females, while the same males with this paste dis-
solved off did.

Mayer now tried to test the selective action of the female.
The male promethea has blackish wings while the females
are reddish-brown. In accordance with the theory of
sexual selection, the peculiar coloration of the male should
be due to the selection of dark-coloured males, so that
under this influence the males would become, in successive
generations, darker and darker until the present coloration
has been attained. Mayer’s own account of his experi-
ments and conclusions to test the preferences and selective
action of the females is as follows:

“In order to test this hypothesis I cut off the wings of a
number of females, leaving only short stumps, from which
all the scales were carefully brushed. Male wings were
then neatly glued to the stumps, and thus the female pre-
sented the appearance of a male. Under these circum-
stances the males mated with the female quite as readily as
they would have done under normal conditions.

“T then tried the experiment of gluing female wings upon
the male. Here again the mating seemed to occur with
normal frequency, and I was unable to detect that the
females displayed any unusual aversion toward their
effeminate-looking consorts.

“It 1s also interesting to note that normal males pay no
attention to males with female wings.

“In another series of experiments the wings were cut
entirely off of males and females and the scales brushed
off their bodies; and yet these shabby males were readily
accepted by normal females, nor could I see that normal
males displayed any aversion to mating with wingless
females.

DARWINISM ATTACKED. 123

“We are therefore forced to conclude that the melanic
coloration of the male has not been brought about through
the agency of sexual selection on the part of the female.”

More recently Mayer (and Soule) * repeated these experi-
ments on a more extensive scale and with some variations

woe in character. Fifteen hundred cocoons of
Soule’s experi- Promethea were collected in the winter of 1go1-
ae o2 and hung in trees so that the issuing moths
might fly about unconfined. “About six hundred males
emerged from the cocoons and the wings of about one-half
of them were painted with scarlet or green ink, while the
others were allowed to remain normal in colour. It was
evident that the males whose wings were scarlet and green
succeeded fully as well in their attempts to mate as did the
normal males.”

Experiments were also tried with the moth Porthetria
dispar, in which the male is brown and the female white.
The experiments showed that males with wings painted
scarlet or green were accepted as readily as normal males,
but that males with the wings cut off were more apt to meet
with resistance from the females than perfect males were.
From these experiments Mayer and Soule conclude that the
mating instinct in the males of C. promethea and P. dispar
is a phenomenon of chemotaxis. Sexual selection on the
ground of colour alone does not affect it, and there is no
associative memory connected with it.

To these experiments may be added the observations of
Douglass,*” who found that females of the wall-lizard,
Lacerta muralis, showed no preference what-
ever among the variable patterns exhibited by
males in breeding-coat. Diurigen ** observed
that male lizards without tails are accepted readily by
females.

Finally, also, of the nature of objections to the sexual
selection theory are the replacing or substutionary explana-

Experiments
on lizards,

124 DARWINISM TO-DAY.

tions of secondary sexual characters which various biol-
ogists have offered. These explanations will be presented

Alternative ex- in some detail in chapter xi, which is devoted
ee ar to an exposition of the various alternative
characters, theories proposed to replace or partially to re-
place the Darwinian theories. It must be sufficient to say here
that the theories proposed to account for secondary sexual
characters mostly rest on one or both of two principal basic
assumptions; first, that the secondary sexual characters are
produced as the result of the immediate stimulus (naturally
different) of the sexually differing primary reproductive
organs, this stimulus being usually considered to result
from an internal secretion of the genital organs acting on
certain tissues of the organism; and, second, that the males
in most species possess an excess of energy which manifests
itself in extra-growths, extra-development of pigment,
plumage, etc., and that displays by the males of special move-
ments, sound-making, etc., are direct effects or manifesta-
tions of sexual excitation. To these explanations should be
added the rather far-fetched one of Emery, who believes that
many cases of secondary sexual differences are explained by
the sudden appearance (mutation) of another form of male
or female, the persistence for a while of the two forms side
by side, as now exists in numerous dimorphic species (espe-
cially among insects), and then the gradual dying out (kill-
ing out by natural selection) of one of the two old original
forms (the one like the other sex), thus leaving the other,
or aberrant form. The ideas of Cunningham,” who does.
not believe that any selection of fortuitous variation can
account for secondary sexual characters, may also be re-
ferred to. In a book of over three hundred pages this
author lists and describes—according to principal animal
groups—a host of secondary sexual characters, and pro-
poses a theory to account for them. “The direct effects,”
writes Cunningham, “of regularly recurrent stimulations are

DARWINISM ATTACKED. 125

sooner or later developed by heredity, but only in associa-
tion with the physiological conditions under which they were
originally produced. This is the explanation of the limita-
tions of particular modifications not ‘merely to particular
species or kinships, but to particular periods in the life of
the individual, to a particular sex and even to a particular
season of the year in that sex.”’ The author believes that an
examination of secondary sexual characters shows that they
develop at places and in parts which are at the time of
sexual excitement unusually directly stimulated by exertion
or contact or use. These secondary sexual characters are
“in many cases not merely limited to the period of mature
life but actually to that part of the year in which the repro-
ductive organs are active, that is to the breeding season.”
In closing this chapter given up to objections to the Dar-
winian theories of natural and sexual selection, attention
may be called to Wolff’s ** objection to natural
Importance of selection based upon the dependence of the na-
the sexual selec- . :
tion theory asa tural selection theory on the sexual selection
support ofthe theory for explanation of the existence of orna-
natural selection
theory, mental characters, and of all these secondary
sexual characters, which are useless or even
apparently disadvantageous in the life-and-death inter-
‘specific struggle for space and food. As Wolff looks on the
‘sexual selection theory as wholly discredited, he finds this
necessary dependence on it by believers in natural selection
for the explanation of those characters just mentioned
strong evidence for the weakness of the natural selection
theory. —
APPENDIX.

* Kramer, Paul, “Theorie u. Erfahrung ; Beitrage zur Beurtheilung
‘des Darwinismus,” 1877, Halle. An interesting paper criticising
‘the selection theories from two points of view; first, on the basis of
a mathematical treatment of the Darwinian hypothesis (especially
that of sexual selection), the author taking Darwin’s premises and
-by a mathematical handling of them showing that they do not lead

126 DARWINISM TO-DAY.

to the Darwinian conclusions; and, second, on a basis of the care-
ful scrutiny of the facts of secondary sexual differences, the author
finding sexual selection wholly unable to account for the great
majority of secondary sexual characters among animals.

7 A ate, x, “Uber die Bedeutung des Darwin’schen Selections-
prinzips,”’ pp. 107-111, 2d. ed., 1903, Leipzig.

* Darwin outlined the theory of sexual selection in the “Origin
of Species” (1859), but first treated it at length in the “Descent of
Man” €Parts- Il :and Ill), 187%,

* Wallace, A. R., “Tropical Nature,” chap. v, 1878; and “Darwin-
ism,’ chap. x, 1891, London.

* Doane (Ent. News, Vol. XVIII, pp. 136-138, 1907) has described
the striking behaviour during mating of certain Dolichopodid flies
(Scellus virago, n. sp.) observed by him on the salt marsh flats
of San Francisco Bay, near Stanford University. In these matings
it is the female which is the active sex in pursuing and exciting
the other.

* See note 2.

"Morgan, T. H., “Evolution and Adaptation,” chap. vi, 1903,
New York. This chapter is an exhaustive attack on the theory of
sexual selection.

* Mayer, A. G., “On the Mating Instinct in Moths,” Psyche, Vol.
IX, pp. 15-20, 1900.

°* Mayer, A. G., and Soule. C. G, ‘Some Reactions of Cater-
pillars and Moths,” Jour. Exper. Zool., Vol. III, pp. 427-431, 1906.

*? Douglass, N. G. “On the Darwinian Hypothesis of Sexual
Selection,’ Nat. Science, Vol. VII, pp., 398-406, 1895.

‘' Duirigen, ‘““Deutschlands Amphibien u. Reptilien,” p. 89, 1897.

* Cunningham, J. T., “Sexual Dimorphism in the Animal King-
dom,” 1900.

‘8 Wolff, Gustav, “Beitrage zur Kritik der Darwin’schen Lehre,”
p. 21 ff., 1898, Leipzig. A bitter but keen and trenchant critical ex-
position of certain weaknesses in the selection theories. He criti-
cises the theory of sexual selection in the following words:

“An diese Falle reiht sich vielleicht am besten die Betrachtung
der Folgen, welche frithzeitige Sterilitat auf die Ausbildung von

Wolf's exposi- sekundaren Geschlechtscharakteren ausubt. Wir kon-
tion of weak- nen ja diese Erscheinungen auch in gewissem Sinne
nesses insexual zu den Rickbildungen rechnen; sie haben aber insbe-
selection. sondere auch das mit den vorigen Fallen gemeinsam,
dass wir hier ebenfalls einen im individuellen Leben des Organismus
sich abspielenden Vorgang beobachten konnen, der nach der Selek-
tionstheorie nicht eintreten durfte.

“Nach der Selektionstheorie entstehen ja sekundare Geschlechts-

DARWINISM ATTACKED. 127

merkmale dadurch, dass eben Individuen des einen Geschlechts, bei
welchen durch zufallige Variierung eine Andeutung solch eines
Merkmals da war, mehr Chancen hatten, sich fortzupflanzen und
diese Eigenttmlichkeit auf die Nachkommen ihres Geschlechts zu
vererben, von denen dann durch den gleichen Prozess immer
diejenigen zur Fortpflanzung ausgewahlt wurden, welche die betref-
fende Eigentiimlichkeit am starksten besassen. Es soll also zwischen
jenen Gebilden und dem Geschafte der Zeugung an und fiir sich
nicht der geringste Zusammenhang existieren. Dann ist aber
schwer erklarlich, warum jene sekundaren Geschlechtsmerkmale
sich haufig nur zur Zeit der Geschlechtsthatigkeit bilden und nachher
wieder verschwinden, wie z. B. der Hochzeitskamm der Tritonen.
Aber geben wir einmal zu, das sei bloss ein zufalliges Zusammen-
treffen, indem eben diejenigen zur Fortpflanzung gelangten, welche
gerade zufallig um die Zeit der Brunst eine bald wieder zufallig
verschwindende Verstarkung des Kammes besassen. Es ist zwar
unmoglich, sich dies, insbesondere das Verschwinden des Kammes,
vorzustellen, weil ja, wenn auch das spatere Verschwinden des:
Kammes dem Tiere irgend einen Vorteil gebracht haben sollte,
dieser bei der Selektion in keiner Weise sich geltend machen konnte,
oder doch nur in Bezug auf das Individuum aber nicht auf dessen.
Nachkommen, aber nehmen wir einmal an, das sei alles in Ordnung:.
wie erklart sich dann, dass, z. B. beim kastrierten Hirsch kein
Geweih sich entwickelt, dass der kastrierte Mensch hohe Stimme
behalt, keinen Bart bekommt u. s. w., u. s. w.?

“Auch andere Riickbildungen, welche nach AufhGren der Ge-
schlechtsthatigkeit normal sich einstellen (z. B. Aufhéren der Flim-
merbewegung im Uterus des Weibes nach Aufhoren der Menstrua-
tion, Verlust der Flugel nach der Begattung bei Insekten,* etc. ), bieten.
der Selektion die grossten Schwierigkeiten, denn wenn hier die
Ruckbildung einen Vorteil bote, welcher die Auswahl der Indi-
viduen, bei welchen diese Riickbildung auftrat, herbeifiihrte, so
konnte dieser Selektionsprozess doch erst nach der Fortpflanzungs-
zeit eintreten, auf die nachfolgenden Geschlechter daher von keinem
Einflusse mehr sein.

“Der unbestreitbare Zusammenhang, welcher zwischen der Ge-
schlechtsthatigkeit und den sekundaren ’ Geschlechtsmerkmalen
besteht, ist nun aber nicht etwa durch das Wort “Korrelatior’
erklart. Es ist natiirlich richtig, dass eine Anderung irgend eine
andere im Gefolge haben kann, dass es also korrelative Abande-
rungen giebt, aber ist denn damit vielleicht erklart, dass eine
bestimmte zweckmassige Abanderung nun auch eine andere fir

*In diesem letzteren Fall ist vielleicht doch ein Vorteil ftir die
Art durch Vermittlung der Brutpflege denkbar.

128 DARWINISM TO-DAY.

den jeweilig vorliegenden ganz speziellen Fall nititzliche Abande-
rung bedingt? Korrelative Abanderungen beziehen sich ja in den
meisten Fallen, wo wir von solchen sprechen, auf ganz bestimmte
Verhaltnisse der Aussenwelt. Sich zur Erklarung solcher Erschein-
ungen mit der Konstatierung eines Gesetzes der Korrelation
zufrieden geben, heisst einfach eine praestabilierte Harmonie
zwischen der Entwicklung der Organismen und den Verhaltnissen
der Aussenwelt annehmen. Das Ratselhafte ist ja zunachst nicht
der Umstand, dass es uberhaupt Korrelationserscheinungen giebt
(wenngleich wir naturlich auch hierflr ebensowenig, wie
fur irgend eine andere Lebenserscheinung eine Erklarung haben),
sondern der Umstand, dass eine Eigenttimlichkeit eine andere
korrelativ im Gefolge hat, die eben gerade fiir besondere
aussere Zwecke vorteilhaft ist. Hier kann die Selektionstheorie
nichts ausrichten, denn der Selektionsprozess hat doch keinen Ein-
fluss auf die Variierungsgesetze, zu welchen die Korrelationsge-
setze gehoren; diese mtssen vielmehr vorausgesetzt werden.

“Es giebt ubrigens Thatsachen, die mir darauf hinzudeuten schei-
nen, dass die korrelativen Beziehungen noch viel verwickelter sind,
und dass korrelative Beziehungen gar nicht immer auf die Ent-
stehung korrelativer Abanderungen zurtickzufthren sind, sondern
dass, was ja noch viel ratselhafter ist, eine Korrelation erst sekundar
erworben werden kann, wie folgendes Beispiel zeigen diirfte.

“Von den drei verschiedenen Individuen des Bienenstaates hat
nur die Arbeitsbiene an der Innenflache des Tarsus regelmassige
Borstenreihen, sogenannte Burstchen. Da die Arbeitsteilung immer
eine hohere Differenzierung ist, so kann es keinem Zweifel unter-
liegen, dass urspriinglich bei allen Formen die Beine gleich waren.
Kaum zu entscheiden dtrfte wohl die Frage sein, ob ursprunglich
sich die Btirstchen sowohl bei mannlichen als auch bei weiblichen
Individuen differenzierten. sodass das Fehlen derselben bei den
Drohnen als Riickbildung betrachtet werden miusste, oder ob die
Biirstchen gleich von vornherein als sekundares Geschlechtsmerkmal
der Weibchen auftraten. Im erstern Fall ware also die Bildung
primar in keinerlei Korrelation zum Geschlechtsapparate gestanden,
diese miisste vielmehr erst spater erworben worden sein. Im
zweiten Fall waren die Biirstchen als zum Geschlechtsapparate
korrelative Bildungen entstanden, aber in beiden Fallen musste
eine Anderung des Korrelationsverhaltnisses eingetreten sein, die
Korrelation musste namlich eine reziproke werden: die Entstehung
von Biirstchen ist zwar an das weibliche Geschlecht geknupft,
jedoch in der Weise, dass die Biirstchen nur auftreten, wenn die
Geschlechtsorgane nicht zur Ausbildung kommen.”

CHAPTER Vik.
DARWINISM DEFENDED.

In taking up the defence of Darwinism it should be noted
in the first place that the anti-Darwinians are without the
walls; that theirs is the burden of attack; that
Renata. against them is the presumption of right. The
defendersof § J)arwinians are in the castle, theirs simply the
Darwinism. : . ; ; é
necessity of withstanding or repelling really
significant and truly threatening attack; theirs the strength
of possession and the presumption of truth. Much anti-
Darwinism is futile and easily answered; much was an-
swered by Darwin * himself before ever the anti-Darwinians
formulated it; much other anti-Darwinism is directed against
a position which Darwinism, true Darwinism, has long seen
the inadvisability, indeed the impossibility, of holding.
With certain concessions made, what use of further struggle
over them? Thus by answering briefly the insignificant and
undamaging part of anti-Darwinian attack, or by referring
to Darwin’s own answers of this, and by indicating clearly
and definitely the concessions that Darwinism is ready to
make, has made, indeed—these humiliating concessions, if
humiliation is in them, only being made necessary because

*Darwin’s anticipation of the criticisms of his theories, and his
own open-minded and detailed answers to these criticisms, should,
of course, be held clearly in mind by any student of fiur-und-
gegen Darwinismus. but many of these answers concern objections
which present-day Darwinism has largely conceded as valid, and
most of the others touch matters on which modern biological re-
search has thrown much new light. So that it is perhaps fairer
to the Darwinian theories to set out the attitude of present-day
Darwinians. For a detailed critical consideration of Darwin’s own
answers, see Morgan, “Evolution and Adaptation” (1903).

129

130 DARWINISM TO-DAY.

of the ill judgment and rash enthusiasm of certain too
ardent and too conspicuous friends of Darwinism, the so-
called neo-Darwinians—with this salutary restriction of
diffuseness in account, “Darwinism Defended” may be con-
fined to fewer pages than have been devoted to “Darwinism
Attacked” without suggesting by this brevity any necessary
weakness in the Darwinian position.

Let us give our first attention to the Darwinian conces-
sions—those concessions which the biological world has

Mechs practically agreed have been made necessary by
against ultra- the steady criticism of the exaggeration and
oe magnification, almost wholly post-Darwinian in
appearance, of the Darwinian factors in evolution. It is
strange, but wholly true, that the modern reaction and revolt
against Darwinism is chiefly due to the activity and attitude
taken by certain of its over-ardent friends. Weismann, by
denying validity to any other evolutionary factor than the
natural selection of purely congenital variations, and by the
development to an illogical and untenable extreme of his
theory of the independence and continuity of the germ-
plasm, precipitated the revolt and furnished the enemy with
the very weapons needed to overcome neo-Darwinism.
The evolution champion Haeckel, although not at all a
Weismannian Darwinian, has also by his daring and reck-
less speculative development of certain phases of evolution-
ary thought, especially in its relation to sociology and
religious philosophy, and by his obstinate adherence to, and
reiteration of, certain long discredited more strictly biological
dogmas of evolutionary science, contributed to
produce an irritation and antagonistic activity
among biologists, especially in Germany, which has helped
make many friends for the anti-Darwinian party. “Der
Haeckelismus in der Zoologie,’* as Semper originally
phrased it, is the object of a curiously bitter and often-
expressed contempt in German biological circles. I fancy

Haeckel.

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DARWINISM DEFENDED. 131

that this feeling really depends not so much on Haeckel’s
attitude and speculative writing in zoology as in his unpar-
donable intrusion into politics and religion; the Social-
Democrats and the Free-Thinkers have found a helpful and
willing scientific champion in Haeckel. And this is sin
superlative in rigorous minds! As a matter of fact, how-
ever, biologists generally are agreed that Haeckel’s daring
speculations and reckless progress in advance of positions
grounded on observed fact have been, in a way, always repre-
hensible and dangerous to the fair fame of biological science.
But, to my mind, biologists may also fairly agree that this
very activity and speculative daring of Haeckel have in-
spired much genuine biological investigation (for the sake
of denying or confirming his speculations) and have led to
a salutary reactionary critical attitude toward other biologi-
cal speculations and hypotheses. It is a rare ism in any
science or philosophy that yields nothing good.

Weismannism is wholly different from Haeckelism. It
has only in common with it that it is, in part, also daringly
speculative. But the speculations primarily interest neither
Free-Thinkers nor Social-Democrats. They have to do
with the ultimate structure and behaviour of protoplasm,
especially germinal protoplasm, and with the intimate proc-
esses of heredity and variation.

Weismann first attempted to free Darwin’s general theory
of modification and species-forming from all taint of La-
marckism; an attempt which resulted in his
apparently successful overthrowal of the com-
monly accepted theory of the inheritance of
acquired characters, a theory or assumption which is a
fundamental and indispensable part of the general Lamarck-
ian theory. (Lamarckism and the inheritance of acquired
characters are explained and briefly discussed in chapter x of
this book.) On the strength of this success Weismann pro-
posed the doctrine of the Allmacht of natural selection; that

Weismann’s
theories.

132 DARWINISM TO-DAY.

is, that natural selection alone is capable of explaining all the
phenomena and facts of species-forming and descent. At
‘the same time he developed and announced the theory of the
continuity of the germ-plasm,’ which, in a word, is the
theory of an absolute separation of the germ-plasm from
the soma-plasm and consequently the thorough independ-
ence of this germ-plasm from all influence and control of
the soma-plasm, 7. ¢., all that part of the body other than
the germ cells. This carried with it the assumption that
all the phenomena of heredity and variation depended solely
on the germ-plasm and that the germ-plasm of any individual
is derived, unmodified by any somatic influences, directly
from the germ-plasm of its ancestors. This assumption in
turn led to the logical but startling conclusion that all the
capacity or possibility of variation for all time was present
in that primitive ancestral germ-plasm from which the germ-
plasm of all many-celled animals has been derived. But such
a nearly infinite capacity for furnishing variations demanded
the postulation of an equally nearly infinite capacity for ac-
tual physical or structural complexity on the part of the germ-
plasm itself, for biologists insist on a physical mechanism for
all the physiological phenomena they find in life. So Weis-
mann assumed an interesting but invisible and apparently
non-testable composition of germ-plasm out of life-units,
called biophors, grouped into particles of.a second order called
determinants. The biophors are taken to be much larger
and more complex units than chemical atoms, or even than
molecules. They are groups of several to many molecules,
each biophor, however, still ultra-microscopic, and represent-
ing a single characteristic of cell-life. Each biophor is as-
sumed to possess the essential attributes of living substance,
viz., the capacity to assimilate food, to grow, and to repro-
duce itself. The groups of biophors called determinants
are larger, of course, but yet invisible to our best micro-
scopes, and each represents all the characteristics which a

DARWINISM DEFENDED. 133

cell of any particular single kind has. Thus one kind of
determinant represents all the attributes of the red blood
corpuscles, another of the nerve-ganglion cells, another of a
certain type of epithelial cells, and so on. Each determinant
has also the power of assimilating food, growing and re-
producing itself by division. Now the possibility of repre-
senting in the germ-plasm the nearly infinite capacity to
vary characteristic of this plasm has for its physical or
mechanical basis the minute size of the biophors and deter-
minants coupled with the inconceivably many combinations
of different kinds of biophors possible in the make-up of the
determinants which are, as already said, the actual structural
representatives of, or better, controllers or producers of,
the various kinds of body tissue and organs.

These three general assumptions of Weismann, namely,
(1) the composition of germ-plasm out of ultimate life-units
called biophors (grouped into determinants) which deter-
mine all the physical characteristics of the individuals into
which the germ-plasm develops; (2) the isolation (from the
soma) and the continuity (from generation to generation,
from beginning to end) of the germ-plasm; and (3) the
Allmacht of natural selection, which involves the discarding
of all other factors of modification and species-forming than
the natural selection of the slight fluctuating congenital
variations produced (in an unknown manner) by infinitest-
mal changes in the determinants of the germ-plasm—these
three fundamental and important Weismannian assumptions,
accepted more or less nearly completely by Wallace and a

See number of other English biologists, and by a
ism and Neo- few naturalists of Europe and America, con-
Lamarckism. = ctitute the essential position of what is called
neo-Darwinism. This neo-Darwinism immediately found
many capable antagonists, and as most of the antago-
nists were believers in some parts of the general theory
of adaptation and species-forming first proposed by

134 DARWINISM TO-DAY.

Lamarck, their position came to be known as _ neo-
Lamarckism. Herbert. Spencer in Eneland, Packard,
Osborn, and others in America, and Eimer in Ger-
many were prominent exponents of the anti-Weisman-
nian views. The debate was spirited, and engaged many
biological writers, and interested the general reading
public in the larger problems of biology more than it
has been interested at any other time since the great struggle
immediately following the publication of Darwin’s “Origin
of Species.” The best known part of the general debate
was that carried on directly by Weismann and Spencer in
the Contemporary Review (1893 and 1894).
The general result of the struggle between neo-Darwin-
ism and neo-Lamarckism can be fairly stated to be, that
Weismann’s assault on the theory of the in-
secre a heritance of acquired characters was in general
successful; while, on the other hand, the assault
of the anti-Weismannians on the assumptions of the isola-
tion and continuity of the germ-plasm and of the Allmacht
of natural selection forced from Weismann and his follow-
ers, one by one and slowly, such radical concessions as to
make the latter doctrine utterly untenable, and to rob the
other of most of its significance in the consideration of modi-
fication and species-forming. The assumption of the com-
position of germ-plasm out of biophors and determinants
is of course merely an interesting speculation, or tentative
hypothesis, which, because it is untestable by scientific ob-
servation or experiment, cannot be debated to any particular
advantage. Weismann himself, in 1895, definitely conced-
ing that natural selection is radically weak at its base, being
incapable of explaining the beginnings of useful variations
and the development (which actually occurs) of indifferent
ones, proposed a new and radically un-Darwinian theory
under the name of Germinal Selection. This theory (ex-
plained in chapter viii of this book) although including the

ey
ea

DARWINISM DEFENDED. 135

_word selection in its name is fundamentally different from

natural selection in the Darwinian sense, and is indeed
an admission of the existence of variations maintained (not
by means of natural selection) along definite lines, result-
ing in a real orthogenesis. It attempts to offer a causo-
mechanical explanation of such un-Darwinian development.
By the theory of germinal selection, which is based abso-
lutely on the assumption that the plasm is composed of
biophors and determinants or at least of physical life units
of similar type and function, Weismann hopes to strengthen
four weak places in the general position of neo-Darwinism.
The theory explains (1) how in Panmixia (another Weis-
mannian contribution to neo-Darwinism, for account of
which see chapter viii) the degeneration of useless organs
is brought about, (2) how it is that for the continued
development of any certain complex adaptation exactly the
right variations shall appear at the needed time, (3) how co-
adaptation comes to exist, and finally (4) how variations
may come to be developed along fixed lines or in definite
directions without the aid of personal selection. Whether
the theory of germinal selection explains these four things
or not, what is to us for the moment the chief interest of the
theory is that it is put forward by Weismann, who is dis-
tinctly the foremost neo-Darwinian, to explain just these
things. For that makes of these things concessions that the
neo-Darwinians, the ultra-selectionists, feel forced to offer.
It should be noted, however, that perhaps Weismann does
not speak for all ultra-selectionists, for example, Lloyd
Morgan, Ray Lankester, and other English * Darwinians.
Certainly his theory of germinal selection is accepted by
few of them.

On the whole, however, I think I speak perfectly fairly
in saying that the believers and defenders of the natural
selection theory to-day admit in large measure the valid-
ity of those criticisms which are directed at the inca-

136 DARWINISM TO-DAY.

pacity of Darwinism, in its long familiar form, to account
for the development of variations and modifications up
to the advantageous or disadvantageous stage. They admit
also the actual existence, and in abundant measure, of
species differences which are of indifferent character, that is,
of no especial utility, and make the consequent admission
that such species differences cannot for the most part be
explained by natural selection. And they also concede, or
at least most of them, including Weismann, do, the force
of the criticism that the assumption of the occurrence of the
tight variations at the right time is a necessity for the
development by selection of many if not most specialisations
of qualitative and of coadaptive character, which assump-
tion in turn demands an explanation of causes anterior to
selection.

And finally most selectionists concede that selection can-
not make new species by relying on the extremes of series
of fluctuating or Darwinian variations because of the
inevitable extinguishing or swamping of these extreme
variations by inter-breeding with the far more abundant
average or modal individuals of the species. Hence all
those objections recorded in the chapters on “Darwin-
ism Attacked” which have to do solely with this inca-
pacity of natural selection to make use of variations too
small or too few or purely fortuitous, or with the incapacity
of selection to explain hosts of indifferent, non-adaptive
species differences which actually exist, and hence with the
certainty of its not being the only factor, if indeed a prin-
cipal factor, in the formation of species, need not be re-
discussed, at least to any length, in this chapter. We may
also largely neglect those objections which are directed
against the purely hypothetical assumptions and the extreme
positions of the neo-Darwinians. Many of these assump-
tions, such as that of the absolute isolation and independence
from the soma of the germ-plasm, are not a part of Dar-

DARWINISM DEFENDED. 137

winism proper, and the extreme position of the believers in
the Allmacht of selection was certainly never taken by Dar-
win himself. In fact, most of neo-Darwinism has been.
deserted by its one-time followers, and most conspicuously
and perhaps most radically by Weismann himself.

Thus, with these two categories of objections listed in
the “Darwinism Attacked” chapter put to one side, for the
moment at least, by admitting the validity of one category
and showing the inapplicability of the other as regards its

relation to true Darwinism, we have left to us.
The objections to consider those remaining objections which
needing answer. ; eqe
are made (1) against the capability of selec-
tion’s making any use at all of the familiar and always
occurring fluctuating variations called Darwinian, (2)
against its capacity to explain coadaptive and highly com-
plex adaptations, especially those which seem as if they
could be of advantage to the organism only in fully
developed or specialised state, (3) against its inability to
account for overdeveloped specialisations, (4) against the
possibility of selection’s explaining qualitative differences in
species, and many-branched descent (quantitative differ-
ences and linear descent seeming to be the only kinds pos-
sible to it), (5) against its capacity to explain complete
or extreme structural degeneration of useless organs and
parts, (6) against the reality and extreme rigour of the
struggle for existence and personal selection (an essential
foundation of the selection theory), (7) against the sexual
selection theory, particularly in its capacity as a supporting
prop of the natural selection theory, (8) against the reliance
by the selectionists on the homology or analogy which they
hold to exist between natural selection and artificial selec-
tion, and finally to consider those curiously positive and
definite declarations of such radical anti-Darwinians as
Wolff, Korschinsky, and others that natural selection is a
vagary, having no claims to existence either on a basis of

138 DARWINISM TO-DAY.

observation or logical reasoning, or that if it exists its whole
influence is directly inimical to changes and evolution rather
than of a nature to produce and foster them. The most
comprehensive, fairest, and most effective recent attempt
to gather together and meet seriatim the objections and
criticisms of Darwinism is (as already stated in the chapter
on “Darwinism Attacked”) that of Ludwig Plate,’ and I
have therefore given considerable space in this chapter to
direct quotations from the answers and discussions of this
modern Darwinian champion.

The objection made that natural selection can make no use
at all of the small fluctuating Darwinian variations is really

Poke wider application of the really valid objection
objection that that such variations cannot, or can only rarely,
fuctuating vari- Offer material for the production by selection of
ations are too
slight tobeof new organs and that for many adaptations
pi bea they are too slight to be of use and hence
cannot serve as handles for selection. As a matter of
fact, however, many adaptive modifications are purely quan-
titative, not necessarily involving any qualitative change
at all. Increase in general size, or in any one dimension
of an organ or part, meaning often an increase of strength
on the part of the animal, in the capacity for aggres-
sion or defence, in swiftness, in flight, running or swim-
ming, in reaching or digging or climbing or leaping—
such an adaptive modification might well be brought about
by selection of even very inconsiderable enlargements or
strengthenings of one or more organs or parts. Wherever
the modification is in a directly linear path, and an advantage
is possible through even slight advances or regressions along
this line, natural selection will find in the Darwinian varia-
tions a means of fostering and perfecting this modification.
There are just two requirements necessary for the Darwin-
ian variations to meet in order to serve as handles for
natural selection: they must be variations actually suff-

DARWINISM DEFENDED. 139

ciently useful and advantageous to turn the scale in the intra-
or inter-specific struggle for existence in favour of the
individuals possessing them, and they must occur in suffi-
ciently many individuals to avoid being swamped or
extinguished by cross-breeding: that is, they must be useful
enough to be selected and numerous enough to perpetuate
themselves. Do Darwinian variations ever meet these re-
quirements? Unfortunately our proof is rather indirect:
observation reveals their abundance, but does not actually
show their utility.” To answer the question our judgment
and reason, based on our knowledge and experience of the
existing conditions of animal and plant life, will have to
be trusted for answer. How real is the rigour; how keen
the struggle ; how crowded the square yard or square mile;
how great or how little must be the differences in a part to
give a life-or-death decision in the competition? Each
naturalist must answer this for himself, and the layman
must take the general consensus of opinion of the natural-
ists, if there is one, for his answer.
The objection to the linear and quantitative character of
the Darwinian variations has been recently especially urged
by de Vries in connection with his exposition
eee a of the theory of species-forming by mutations.
cerning the The selection theory reckons with linear hence
linear and quan- ; ate Sate
titative charac- Strictly quantitative variations, says he, and yet
ees is presumed to create new forms for which in
reality qualitative variations are necessary as
a basis, so that in fact selection can only increase or
diminish, add to or subtract from characters already in
existence and cannot create anything new, this appear-
ance of new characteristics being, however, precisely the
principal peculiarity of new species, taken by and large. This
position of de Vries has been discussed by Plate’ as follows:
“T call attention in advance to the fact that de Vries
understands by ‘linear variations’ what are more usually

140 DARWINISM TO-DAY.

known as individual, fluctuating or continuous variations.
He has chosen this name because the single characteristic
can change toward but two directions; that is, toward the
plus, or toward the minus direction. In contrast to this
kind of variation stand the sudden and discontinuous leap-
like changes or mutations which have been for the first
time carefully investigated by the praiseworthy labour of
de Vries, hitherto having been familiar indeed under the
names ‘single variations’ or ‘sports,’ but little studied. Con-
cerning these linear variations de Vries writes: “The statis-
tical method of the study of variation has now been so
generally followed as to make its principles familiar without
further discussion, and they may be considered as accepted.
The chief principle indicated by the use of the frequency
curves is that the characteristics vary in but two directions,
that 1s toward plus or toward minus. The old vague con-
ception of an all-sided variation of the single characters
has disappeared of its own self.’

“As highly as I appreciate the great service of de Vries
in relation to our knowledge of the suddenly appearing
changes, heritable in high degree, I must nevertheless op-
pose him in his conclusions touching the selection theory.
In the first place this theory does not reckon alone with
linear variations, but also with mutations, if they appear,
for it takes the changes as given material without troubling
itself about differences in their mode of origin. In the
second place it is not correct that a character cannot so
change itself through simple addition or reduction that it
may not be, in the customary classificatory limits, looked on
as a new character. A smooth leaf, a leaf with few small
hairs, and one with a thick wool show only linear variations,
but in spite of that they may very well serve as character-
istic of different species. Nearly related butterflies—recall

the Vanessas and Lycenas—often show the same funda- -

mental characters of pattern and form, so that they are dis-

DARWINISM DEFENDED. 141

tinguished only by plus or minus variations. Indeed one
may consider the whole endless manifoldness of organic
combinations as only representing greater or lesser num-
bers of atoms of the same few elements which are bound to-
gether in one molecule. In the third place the statistical
studies of variation have not shattered in any respect the
conception of an all-sided variation of the single characters,
but indeed on the contrary have rather shown that all the
parts and attributes of organisms that are accessible to
observation appear to us more or less different in different
individuals. This all-sided variability has nothing to do
with the statement that each single variable element can
vary always only toward plus or toward minus. Blue
flower petals can appear more or less blue and at the same
time reveal their indeterminate, fortuitous, or all-sided
variability in differences of form, hairiness, thickness,
structure, etc. The same indeterminateness which de Vries
claims for his mutations is characteristic also of linear
variations.”

Tayler,” a Darwinian defender, has discussed this objec-
tion as follows: “This objection appears to me to be one of
the most weighty of all the objections which have been raised
to the selectional hypothesis, and it is further an extremely |
difficult objection to satisfactorily reply to; first, because it is
almost impossible to say in what form of organism the earli-
est variations appeared, and without this no judgment on the
value of any small variation can be of use; secondly, it is
equally essential to know the kind of environment which
such an organism was living in; and lastly, if we were
fully acquainted with the character of the organism and its
environment it would still be difficult to form any adequate
opinion on the value of such a variation, owing to the fact
that this apparently simple organism would differ so widely
from our own functional activity and life that any conclu-
sions formed on comparative methods of testing its powers,

142 DARWINISM TO-DAY.

etc., would be extremely likely to be fallacious. If, however,
we keep in mind the facts that (1) the whole and not merely
a part of the organism is selected, and that, therefore,
each variation does not require to be of the same value as if
selection depended on it alone; (2) specialisations are
largely quantitative, between man at one extreme of de-
velopment and a simple unicellular organism at the other,
the difference, though very great, is mainly due to the fact
that man is a huge multicellular colony; this difficulty will be
much simplified. To estimate the quantitative difference it is
necessary to endeavour to determine the specialisation of an
individual cell in one of those collective specialisations or
organs: the difference between a cell in, for instance, the
cerebral cortex of man and the character of an ameeba is no
doubt great, but the amceba reacts to stimuli, though in a
less specialised form, just as the cortex cell does ; in the same
way the reaction to light in the mammalian eye is not a new
development—it has its beginnings in the preference for
light or darkness shown by many unicellular organisms.
These two points, that selection is organismal and that
specialisations are as, or more, largely quantitative than
qualitative, weaken if they do not abolish all those diff-
culties to natural selection that are founded on this objec-
tion, and it is further necessary to recollect that no specialisa-
tion has yet been found which has not a primitive counter-
part in the earliest known forms of life.”
With regard to the objection that because natural selec-
tion working with fluctuating Darwinian variations 1s
working only with linear or quantitative varia-
Answer tothe tions and therefore cannot produce many-
objection that
selection cannot branched descent (which is certainly the kind
‘samen lent Of descent that exists) but only straight-line or
and discontinuity mono-typic descent, it is obvious that the Dar-
ciaeataa winian answer to this is partly that of the
answer to the objection discussed in the last paragraph. In

“it

pn > 7
en 3
n
1

DARWINISM DEFENDED. 143

addition it is partly that of the answer to the objection to
be mentioned in the next sentence. This related objection
is that while natural selection may produce continuous
gradatory adaptive change or evolution it cannot produce
discontinuity in the series, 7. e., cannot produce separated
distinct species. This objection receives an answer which
is of the nature of an admission that natural selection wholly
unaided really cannot differentiate species. It must call to
its aid some isolation or segregation factor, and as isolation
is certainly most commonly effected through migration and
geographic means, it is usually this factor of geographic
isolation that natural selection must be accompanied by to
form new species. As Plate says: “Any particular phase
of the struggle for existence extinguishes all those indi-
viduals which do not possess certain absolutely necessary
characteristics. By this means there is produced a common
type. And only when some means of isolation is added can
the splitting of the species into two or more forms result.
Natural selection can only transform a species gradually
and develop it in a continuous forthright line; alone it cannot
produce a divergent, tree-like evolution. This results from
geographic, biologic, or sexual isolation, which is in most
cases a form of the extensive manner of working of the
struggle for existence. But selection can aid in the differ-
entiation of a species into two or more forms, as the following
examples show. When all average or median-sized in-
dividuals of a species are killed out there remain only the
smallest and the largest, by which we may assume that the
first are saved because they can most readily conceal them-
selves, while the latter find in their ereat size a sufficient
protection. On the ground of this difference in size perhaps
both forms will be inclined to keep apart from each other
and if to this is added a somewhat differing habit of life,
two races can arise which in course of time will become
distinct species. From a butterfly kind of very variable

144 DARWINISM TO-DAY.

‘colour-tone all brown individuals might disappear for some
special reason while both the lighter and darker individuals
might persist. Now if in consequence of this contrast a
racial feeling should develop between the light individuals
on the one hand and the dark ones on the other, the differ-
entiation into two species is already begun. If a snail species
living in fresh water is so harassed that it can only maintain
itself when its individuals move either into the region be-
tween tide-lines or into the deeper water, this would lead to
morphological differentiation, as we can indeed actually note
in the case of the chitons.”’
The objection that the existence of coadaptive and highly
complex adaptations, especially those which seem as if they
could be of no possible advantage to their pos-
Prarieneum sessors except in their present fully developed
cerning complex Or specialised state, is one which. unfortunately
aera cannot be definitely refuted or proved by ever
so much ingenious explaining or discussion in
the face of the lack of what we certainly do not now
possess, namely, direct observational or experimental evi-
dence. For such specialisations as elaborate mimickry, or
the electric organ of the torpedo, etc., which are of appa-
rent advantage only in perfected state, the selectionist is
forced to admit that the objector has apparently a good case,
but for the gradual specialisation of many highly complex
structures and specialisations through the long-continued
selection of slight advantageous variations, Darwin and his
followers have offered ingenious and plausible explanations.
For the case of so complex and coadaptive a specialisation as
the eye and its function in the vertebrates or in the insects
and crustaceans, the possible evolution, by slight additions
and modifications, from simple pigment fleck to the present
marvellous visual organ, a logically irrefutable Darwinian
argument can be made out on the basis of the real and
constant utility and advantage of even very slight steps

DARWINISM DEFENDED. 145

forward. And so with many other complex specialisations,
although in almost all these cases it is necessary, as Darwin
says, to let the reason conquer the imagination. That is, the
reasoned explanation explains, although one recoils con-
stantly before the almost inconceivable actuality of the
phenomenon.

Plate has recognised this objection as one of the really
weighty ones and has given much attention to its considera-
tion. His conclusion is that it is necessary to rely to a
ereater or less extent on the Lamarckian factor of the
inheritance of somatogenic characters acquired in the life-
time of the individual through the effects of use, or disuse,
or other functional stimuli. This is, of course, direct aban-
donment of the position maintained by such strict selection-
ists as Weismann and Wallace, although Weismann himself,
in order to answer the objection without having recourse
to reliance on Lamarckian factors, introduces his new
theory or hypothesis of germinal selection to aid natural
selection in the difficulty presented by the objection. Lloyd
Morgan’s* answer to this objection consists chiefly of the
formulation of the theory of orthoplasy (explained in chapter
viii of this book). It is, briefly, that every organism, from
its somatic and germinal aspects, exhibits two tendencies
of variability. The somatic variability is determined largely
or at least modified largely by environmental influences ;
therefore those organisms whose somatic tendency is pre-
dominantly plastic will survive under altered conditions of
environment, where those organisms of a less easily mod-
ifiable tendency will be eliminated. Now if somatic changes
rarely or never become germinal, 7.e., are inherited, the mod-
ifications of the parental organisms cannot be transmitted
to their offspring, but those offspring that happen to be
endowed with germinal variations in the same direction
as the acquired but not transmitted modifications would
start their life with a predisposition favourable to their

146 DARWINISM TO-DAY.

environment and therefore favourable to more complete
modification of the somatic side of the organism; this tend-
ency being accumulative under constant conditions, coinci-
dent variability would arise by the process of selective
elimination and preservation, without the need of the
assumption of use-inheritance, which assumption facts
appear to negative.
Against the criticism that natural selection cannot explain
over-developments of specialisation, that is, the carrying
unnecessarily far of advantageous structural
Answer to the . .
objection con- aNd functional development, as illustrated by
cerningover- the great antlers of stags and moose, the micro-
specialisation, . : ; ‘ mee
scopic fidelity of simulation and mimicry, and
the nearly identical equivalence of the right and left halves.
of bilaterally symmetrical animals, the selectionist has little
to offer except the always pertinent questions: Are we sure
that the case in point is one of over-development, of unnec-
essary specialisation? And although the paleo-zoologists
may be pretty emphatic in their declarations that the ex-
tinction of the Irish stag and of the unwieldy cretaceous
reptiles was directly due to over-specialisation, they cannot
prove it. And there you are, says the Darwinist.
The difficulty that natural selection has with structural
degeneration is admittedly a real one. The strict Darwinian
answer has to be that retrogression is produced
Consideration . ; ‘
of the objection ¢ither by reversed selection, that is, that when
concerning de- by a change in the life habits or external condi-
i datas tions a certain function or organ becomes inju-
rious, as in the case of insects on small exposed islands
where the wind might carry the flying ones off into the
ocean, selection, on the basis of advantage, would tend to
preserve the ones most poorly equipped for flight; or it
has to be that when the function of an organ is, because of
change in habit or conditions, once neglected or discon-
tinued, that is, the organ is no longer used, any slight varia-

DARWINISM DEFENDED. 147

tion toward reduction of the organ would be of advantage
because of the saving in food which would be effected! But
this is simply carrying the logic of the principle of advan-
tage to an illogical extreme, an extreme impossible to accept.
So Weismann devised the ingenious explanation of pan-
mixia or cessation of selection to account for degeneration.
‘That is, a rigid and persistent selective activity is as neces-
sary to maintain a specialisation as it was to produce it.
But even Weismann has found this explanation inadequate
and has, therefore, found a final and sufficient explanation
in his new theory of germinal selection. This last theory, a
refinement of Roux’s theory of the battle of the parts, is
ingenious, suggestive, and thoroughly interesting, but un-
fortunately it is founded on certain assumptions concerning
the ultimate make-up of the germ-plasm and the behaviour
of the unit parts of it, the truth of which simply cannot be
tested. A strictly neo-Darwinian answer, that is, one based
solely on selection, is therefore hard to give. Plate,”’ after
an effective adverse criticism of the influence of the Weis-
mannian panmixia as an explanation of the structural reduc-
tion or atrophy of parts, concludes that such reduced or
rudimentary organs are to be explained “through the
inherited effects of disuse, the inherited effects of the influ-
ences of external factors, the inherited effects of the influence
of economy in nutrition, and, in a few cases, through re-
versed selection. The first three principles are cnly admissi-
ble under the assumption of the actuality of the inheritance
of individually acquired characters, and the fourth principle
has only a very subordinate importance.”” This is equivalent
to saying that the strict selectionist has no sufficient answer
to the objection under present consideration. One seems
forced to rely on Lamarckian factors for anything like a
satisfactory explanation of actual structural reduction of
‘useless organs. Tayler,”’ however, offers an explanation
for both ontogenic and phyletic degeneration, based on the

148 DARWINISM TO-DAY.

“known facts of nutrition.” The interested reader may find
this explanation in the appendix to this chapter.
Doubt is expressed by some biologists of the reality and
fierceness of the struggle for existence which is an essential
part of the selection theory. De Vries ex-
Answer to the . . :
objectionsurged Presses the belief that the intra-specific strug-
against therig- ole, that is, the struggle and competition among
our ofselection. » |. . ,
individuals of the same species, has been much
overrated. And a few observations ** have actually been
made which indicate that for certain species this struggle
is at least not rigorous enough to give to the slight Dar-
Winian variations a determining value as to the character
of the surviving individuals. Here again the proof for the
Darwinian point of view is not one so much of observa-
tion—although actual life-and-death combats between indi-
viduals of a single species, and innumerable examples of
the preying of one species on another are familiar—as it is
a proof of reasoning. The fact of an over-production of
eggs and embryos, that is, of reproduction by multiplica-
tion, is undeniable. The lack of existing space and food
for all individuals, if all should live the ordinary span of
life peculiar to the species, is demonstrable by mathematics.
The consequent conclusion of these two established premises
is a struggle for existence. That is the sound Darwinian
position.
The principal answer of the Darwinians to the criticisms
levelled at the theory of sexual selection is, that however
ineffective the theory is to explain many of the
Answer to the 8 ae
objections to the Phenomena it is called on to cover, it is at least
ae so much more reasonable and satisfying as an
explanation of some of the phenomena, that is,
some of the categories of secondary sexual characters, such
as the ornamental plumes and colour-patterns of birds, the
sound-making organs of insects, etc., than any alternative
explanation that has been offered, that until a better expla-

DARWINISM DEFENDED. 149

nation be presented the theory of sexual selection should
not be discarded. That no other explanation of many, if not
most, of the phenomena in question has anything at all
convincing or satisfactory about it, or has met with any.
general acceptance on the part of naturalists, is the plain
truth. If we feel it imperative to give our adherence, with
certain reservations, to any explanatory hypothesis of sec-
ondary sexual characters, Darwin’s theory is the one to
have first claim on us. As a matter of personal opinion I
feel no necessity for any such attitude and am willing to
look on most of the phenomena connected with the general
problem of secondary sexual characters as quite inexplica-
ble on the basis of our present knowledge of bionomics.
The specific answer of Lloyd Morgan** and other Dar-
winians to the objection that choice on the part of the
female assumes an esthetic recognition and preference
which it is doing violence to our knowledge of animal
psychology to assume, should not be overlooked. This
answer is, put summarily, that this so-called choice is one
of impulse, not deliberation: it is an imperative reaction to
a sufficient stimulus: and what determines that the stimulus
from one male shall be sufficient while that from another 1s
not, is the degree of pronouncedness or effectiveness of the
ornament, or call, or behaviour. It is a choice “which is
determined by the emotional meaning of the conscious mean-
ing. And it is the reiterated revival of the associated
emotional elements which generates an impulse sufficiently
strong to overcome her instinctive coyness and reluctance.
It is a perceptual choice arising from impulse rather
than an ideational choice due to motive and volition.”
Regarding Wolff’s argument that an explanation of these
characters is very necessary to the acceptance of the theory
of natural selection there is little to say in rebuttal. Natural
selection confesses itself inadequate to explain those ex-
traordinary characters and conditions by which the males

150 DARWINISM TO-DAY.

of many species of mammals, birds, insects, spiders, etc.,
differ from the females. And if sexual selection does not
explain them then some other explanation is necessary. But
the lack of this explanation does not invalidate the general
theory of natural selection as one of the factors in organic
evolution and indeed one of the most important and far-
reaching ones.
The difficulty of a satisfactory discussion of the objection
that natural selection rests too largely on an assumed likeness
to artificial selection, while the differences in
Consideration the two processes, especially in their results, are
of the objection ;
that natural se- too radical to allow us to rest any confidence
ee on this apparent homology, is, that despite the
assumed analogy Several thousand years through which artificial
hiaertiuai selection has been followed and studied we
still know too little of the real character of it,
especially of its results. Most selectionists now admit that
the argument for natural selection on the basis of its sim-
ilarity to artificial selection has been given too great promi-
nence and relied on too strongly, but that the observed
processes of the one do teach us much of truth about the
unobservable processes of the other the Darwinians firmly
maintain. As Plate says, “The great value of artificial
selection consists in this, that it shows first, that a gradual
cumulation of characteristics in definite directions is actually
possible through successive selections, and second, that it
has afforded us a rich mass of data concerning variation,
inheritance, and the influence of changing intrinsic condi-
tions or influences. When Darwin showed what a high
plasticity the domestic animals possess he built for his
theoretical explanation of descent an indubitable necessary
foundation, for the changes which a domestic animal passes
through in the hands of man must of necessity be able to
be called forth in similar manner in the feral animals by
the creative force of nature, for the domestic animals cer-

DARWINISM DEFENDED. 151

tainly have come from the wild ones. It is also true that
man has made use of only natural factors, and whoever will
compare the extraordinary creatures of the deep sea with
even the most bizarre of our cultivated races, will see that
the fluxing life-conditions of free nature can modify or
reform the animal world in no less degree than the intelli-
gence of man can do it... .

“Recently de Vries,’* in his book on ‘Mutations,’ has tried
to deny the worth of the selection principle, and although
I fully recognise the high worth of his contribution to science
based on such extensive series of experiments, yet I must
oppose him in this position. In various places in the book
he writes that nothing fixed can be produced by selection,
and that therefore it can have no importance as a working
factor in descent. For example, in the introduction (p. 6)
he says: ‘Artificial selection never, as far as experience
reaches, leads to the origin of new complete types.’ The
reversion of modified domesticated races is indubitable, and
de Vries himself has brought forward new illustrations of
this fact which has been so long known. But convincing
proof that natural selection cannot lead to constant forms
cannot be deduced from these observations, because they
refer in all cases to forms which have been highly modified
in the course of a few years or decades, so that the pre-
sumption lies close at hand that there has not been sufficient
time really and lastingly to modify the original heredity
established by centuries. Many facts indicate that the in-
tensity of heredity depends upon the number of generations,
that is, upon time. Long-inherited characters are difficult
to eradicate; recent ones easy. We can, therefore, not
expect to meet such a constancy in the products of a century
as we find in Nature. Many gradually selected races of
doves are now almost entirely constant, that is, no longer
revert to the primitive race when they are inter-bred. The
way in which the reversions appear shows that the duration

152 DARWINISM TO-DAY. —

of time plays an important role in inheritance (heredity).
Schubeler found in his studies of the translation of the
northern boundary of the grain culture that the characters
newly acquired (heavier and earlier ripening seeds) per-
sisted for several generations when the forms were replanted
in the original [more southerly] habitat. De Vries in six
years selected corn which had an average of 20 rows of
kernels instead of the original 12 to 14, and held the plants
at this height of production through five years. When he
then planted seed from a 16-rowed ear, the average of the
ears gathered from this planting was in the first generation
still at 20 rows, and sank only in the next two years again
to 14 to 16. If he had continued his selection longer he
would have arrived at a more nearly constant form. De
Vries himself says: “When the selection ceases, the selected
characteristics drop away and in practically the same length
of time which was necessary for the production of the new
race, that is within a few generations.’ From this it follows
that a domestic race produced by slow persistent selection
through many thousands of generations would show the
same relative constancy or fixity as natural species, the
majority of which also must have originated slowly, for
otherwise the appearance of new species would be often
observed. If one wishes to be very conservative in this
matter one may declare: in the light of our present knowl-
edge we cannot say that artificial selection gives us any safe
means of judging just what degree of constancy [fixity] can
be attained by its means; but it is not fair to say that be-
cause up to the present only a partial constancy has been
reached through artificial selection, natural selection cannot
have led to the production of constant species. All culti-
vated races have been relatively quickly, some indeed very
quickly, selected ** and, therefore, they strike back very
quickly. This, however, need not be assumed for the slowly
arisen products of natural selection.”

DARWINISM DEFENDED. 153

Tayler,’* making a general defence of the natural selection
theory, says: “To realise how far the theory of selection is

Resivecta: capable of explaining the facts of organic evo-
eral defense of lution, it is necessary to bear in mind the
natural selection. Ho<tylates on which the theory is founded.

“tr. It is obvious that natural selection can only act by
preserving or eliminating the complete organism. Selection
must therefore be organismal. This Darwin and other
selectionists have clearly recognised.

“2. As the whole organism must survive, if the favoura-
ble variation or variations are to be preserved, it follows that
certain minor unfavourable variations may also be pre-
served if they happen to exist in an individual which sur-
vives on account of its major favourable variations. And
since no individual is completely adapted to its environment,
it follows that there must be always a variable amount of
residual unfavourable variability in every organism.

“3. This residual unfavourable variability may be of con-
siderable utility under changed conditions.

“4. Complementary specialisation of parts, as Spencer
has shown, is favourable to successful competition, and as it
is the whole organism that is selected or eliminated, it fol-
lows that any weakness of one specialised part, since it would
disturb the balance of all, would be detrimental. The more
complex the organism, the more specialised the structures,
the more dependent one part will be on the others for its
existence, hence a complementary specialising tendency will
be favoured by selection, and therefore all struggles of one
part of an organism with another will be reduced to a
minimum.

“Tt is clear that there must be some underlying criterion
which determines whether any given organism shall be
selected or not, and that criterion must be the net result of
its adaptability to its environment. One organism may con-
ceivably survive, by its possession of a large number of small

154 DARWINISM TO-DAY.

favourable variations, while another may survive in virtue
of a single valuable one, but in each case it would be the
whole value of that organism which determined its survival.
This fact is continually disregarded by opponents of the
neo-Darwinian position, yet this selection of the organism
as a whole is the fundamental postulate from which the
theory of selection starts. Thus it is not uncommon to
read criticisms bearing on the early development of some
organ, in which the inadequacy of selection 1s supposed to
be proved by the writer demonstrating, or believing he has
demonstrated, the fact that the particular variation in ques-
tion must have been too small to be by itself of selection
value. In many cases the particular variation would, no
doubt, if taken alone be, as the objector asserts, too unim-
portant to be selected, but as it is the whole organism that
is selected, it is not logical to make an artificial separation
and study the development of one organ or structure irre-
spective of the other organs with which it is in nature asso-
ciated. Every organ in its evolution must be considered in
relation to the whole cf the particular organism in which
that particular stage of development of that organ 1s found.
Starting, therefore, with this fact that the net value of
adaptability of the whole organism to its environment must
be the basis which determines selection or elimination, it
will follow that certain lines of development will result from
the application of this criterion. In a series of organisms
placed under new conditions, elimination will proceed along
lines essential to bring about a proper adjustment to the
new conditions. If the offspring of these adjusted organ-
isms merely repeated in their generation the characters of
the exterminated as well as of the surviving organisms,
that temporary adjustment would be permanent as long as
the conditions were unchanged. But since the offspring are
produced only by the surviving organisms, selection is con-
tinually raised to higher and higher planes of adaptation,

DARWINISM DEFENDED. 155

and, therefore, as long as conditions remain constant, the
tendency of selection’ must be, as Darwin clearly saw, cumu-
lative. He did not, however, apparently see that from this
cumulative tendency definite variability must arise out of
indefinite.

“Selection in direct relation to climatic conditions is, there-
fore, of very minor importance, while selection. among the °
members of a species and all forms of inter-organismal
selection is of infinitely more importance, since it is this
interaction, produced by the offspring in different degrees
inheriting the advantages of both parents (both of whom
have survived on account of certain advantages), that leads
to the cumulative development and never-ending, struggle
for survival. Darwin came very near to this conception of
definite variability when he pointed out that ‘if a country
were changing the altered conditions would tend to cause
variation, not but what I believe most beings vary at all
times enough for selection to act on.’ Extermination would
expose the remainder to ‘the mutual action of a different
set of inhabitants, which I believe to be more important to
the life of each being than mere climate,’ * and as ‘the same
spot will support more life if occupied by very diverse
forms,’ it is evident that selection will favour very great
diversity of structure.

“Bearing in mind this cumulative action of selection it
will follow that under constant or relatively constant con-
ditions the struggle for successful living will become more
and more selective in character, even if the actual number
of inhabitants remain more or less the same as when the
struggle first commenced. The selection of variations will
thus tend to pass through certain more or less ill-defined,
but nevertheless, real stages. In proportion as the struggle
becomes intense, either from the number or from the in-

*From Poulton’s ‘Charles Darwin and the Theory of Natural
Selection” (Abstract of Darwin’s letter to Professor Asa Gray).

156 DARWINISM TO-DAY.

creasing adaptability of the organisms, or both, certain
major essential adaptations, which were necessary for the
climatic and other more or less comparatively simple con-
ditions, will be supplemented by minor auxiliary variations
which in the earlier stages would not have appeared. And
still later, as more and more rigorous conditions of life were
' imposed, the advantage would tend to rest with those organ-
isms which possessed highly codrdinated adaptations, since
this would entail more rapid responsiveness to environment.

“As evolution advances from the unspecialised to the spe-
cialised, and higher and higher forms of life come into
being, with increasing complexity and specialisation of parts
entailing an increasingly delicate adjustment of those parts
to each other’s needs, the relation of each part to the whole
organism becomes of more and more importance, and it
follows that selection must become more and more general-
ised in its action. No single variation could be of service
to any of the higher forms of life unless it was in more or
less complete harmony with the whole tendency of the
individual. The adjustment of parts and their mutual inter-
, dependence make it essential for adaptation that the relation
of parts be preserved; consequently, correlated minute
favourable variations will tend to be more and more selected
as evolution passes from the unspecialised to the specialised
forms of life. This response of the whole organism should
be still more delicate in those forms of life that are con-
tinually subjecting themselves to changed conditions; hence
this delicacy of adjustment is far more necessary in the
higher forms of animal life than in the more stationary plant.
organisms, and in the developing nervous system of animals
we have just the central adjusting system that is required for
these conditions. Wiuth evolution of type there will thus be
an increasingly definite tendency given to organic, espe-
cially the animal, forms of life, if the acting principle of
evolution has been selectional. Selection is, therefore, able

DARWINISM DEFENDED. 157

to account for the steadily progressive tendency of life as a
whole without calling to its aid any unknown and doubtful
perfecting principle.

“To summarise :—Natural selection, acting on the whole
organism, tends to produce more and more definite tend-
encies in all surviving forms of life, which tendencies are
progressive and continuous in character. Variable condi-
tions, by partially altering the line of selection, induce a
temporary indefiniteness. And lastly, the process of selec-
tion being itself able to be the indirect, though not the direct,
cause of those favourable variations, which it subsequently
selects from, is able to dispense with any subsidiary factors,
provided it has a certain number of elementary properties
of life which afford sufficient material to work with.”

APPENDIX,

1 Semper, Carl, “Der Haeckelismus in der Zoologie,”’ 1876.

27In 1876, Gustav Jaeger anticipated Weismann’s later much-
heralded theory of the continuity of the germ-plasm in _ his
“Zoologische Briefen.”

>For an excellent detailed critical account of these general, as
well as the several accessory theories (amphimixis, polar bodies,
etc.) of Weismann, see Romanes’s “An Examination of Weismann-
ism,” 1893.

*It is of interest to note that the strongest defenders of neo-
Darwinism to-day are the English naturalists. Americans mostly
lean toward neo-Lamarckism; the Germans are divided.

* Plate, Ludwig, ‘““Uber die Bedeutung des Darwin’schen Selec-
tionsprinzip und Probleme der Artbildung,” 2d ed., 1903.

© Prof. Weldon, an English Darwinian, has recorded (Nature, —
Sept. 22, 1898) an extremely interesting and much discussed statis-
tical and experimental study of the presumable action of natural
selection working on slight fluctuating quantitative variations. “I
can only attempt to discuss,” says Prof. Weldon, “the importance
of small variations, and the rate of organic change, in the one case
which I happen to know. The particular case I have myself studied
is the variation in the frontal breadth of Carcinus menas [a small
shore-crab].

158 DARWINISM TO-DAY.

“During the last six years my friend, Mr. Herbert Thompson, and
I have studied in some detail the state of this character in the

Weldon’s ex- Small shore-crabs which swarm on the beach below
periments on the laboratory of the Marine Biological Association,
Carcinus. at Plymouth.

“T will show you that in those crabs small changes in the size of
the frontal breadth do, under certain circumstances, affect the death-
rate, and that the mean frontal breadth among this race of crabs is,.
in fact, changing at a rate sufficiently rapid for all the require-
ments of a theory of evolution.

“In Table IV [omitted], you see three determinations of the
mean frontal breadth of these crabs, expressed in terms of the
carapace-length, taken as 1,000. You see that the mean breadth
varies very rapidly with the length of the crab, so that it was neces-
sary to determine it separately in small groups of crabs, such that
the length of no two crabs in a group differed by more than a
fifth of a millimetre. The first column of the table shows you the
mean frontal breadth of twenty-five such groups, between Io and 15
millimetres long, collected in 1893. These crabs were measured by
Mr. Thompson. The second column shows you the mean frontal
breadth in twenty-five similar groups of crabs, collected in 1895, and
also measured by Mr. Thompson. You see that in every case the
mean breadth in a group of crabs collected in 1895 is less than it
was in crabs of the same size collected in 1893. The third column
contains the result, so far as it is yet obtained, of my own measure-
ment of crabs collected this year. It is very incomplete, because
the 1895 crabs were collected in August and September, and I was
anxious to compare them with crabs collected this year at the same
season, so that there has not yet been time to measure the whole
series. The measurements are sufficient. however, to show that
the same kind of change has taken place during the last three
years as that observed by Mr. Thompson in the interval between
1893 and 1895. Making every allowance for the smallness of the
numbers so far measured this year, there is no doubt whatever that
the mean frontal breadth of crabs from this piece of shore is
considerably less now then it was .in 1895 among crabs of the
same size.*

“These results all relate to male crabs. The change in female

*JT shall, of course, consider it my duty to justify this statement
by more extensive measurement as soon as possible. In the mean-
time I may say that I have measured other small groups of crabs,
male and female, from the same place, at different seasons of the
rt 1896-98, and the results agree with those recorded in the
table

DARWINISM DEFENDED. 159

crabs during this time has been less than the change in male crabs,
but it is, so far as my measurements at present permit me to speak,
going on in the same direction as the change in male crabs.

“T think there can be no doubt, therefore, that the frontal breadth.
of these crabs is diminishing year by year at a rate which is very
rapid, compared with the rate at which animal evolution is com-
monly supposed to progress.

“T will ask your patience for a little while longer, that I may
tell you why I feel confident that this change is due to a selective
destruction, caused by certain rapidly changing conditions of
Plymouth Sound.

“On either side of Plymouth itself a considerable estuary opens.
into the Sound, and each of these estuaries brings down water
from the high granite moorlands, where there are rich deposits of
china clay. Those of you who know Dartmoor will remember that
in rainy weather a great deal of china clay is washed into the
brooks and rivers, so that the water frequently looks white and.
opaque, like milk. Much of this finely divided china clay is carried
down to the sea; and one effect of the breakwater has been to
increase the quantity of this fine silt which settles in the Sound
itself, instead of being swept out by the scour of the tide and the
waves of severe storms. ;

“So that the quantity of fine mud on the shores and on the bot-
tom of the Sound is greater than it used to be, and is constantly
increasing.

“But this is not all. During the forty or fifty years which have
gone by since the breakwater was completed, the towns on the
shores have largely increased their population; the great dockyard.
at Devonport has increased in size and activity; and the ships.
which visit the Sound are larger and more numerous than they
were. Now the sewage and other refuse from these great and
growing towns and dockyards, and from all these ships, is thrown
into the Sound; so that while it is more difficult than it used to be
for fine silt to be washed out of the Sound, the quantity thrown into.
it is much greater than it was, and is becoming greater every day.

“Tt is well known that these changes in the physical conditions.
of the Sound have been accompanied by the disappearance of ani-
mals which used to live in it, but which are now found only outside
the area affected by the breakwater.

“These considerations induced me to try the experiment of keeping
crabs in water containing fine mud in suspension, in order to see
whether a selective destruction occurred under these circumstances.
or not. For this purpose, crabs were collected and placed in a large
vessel of sea-water, in which a considerable quantity of very fine:

160 DARWINISM TO-DAY.

china clay was suspended. The clay was prevented from settling
by a slowly moving automatic agitator; and the crabs were kept
under these conditions for various periods of time. At the end
of each experiment the dead were separated from the living, and
both were measured.

“In every case in which this experiment was performed with
china clay as fine as that brought down by the rivers, or nearly so,
the crabs which died were on the whole distinctly broader than
the crabs which lived through the experiment, so that a crab’s
chance of survival could be measured by its frontal breadth.

“When the experiment was performed with coarser clay than
this, the death-rate was smaller, and was not selective.

“T will rapidly show you the results of one or two experiments.
The diagram [omitted] shows the distribution of frontal breadths,
about the average proper to their length, in 248 male crabs treated
in one experiment. Of these crabs, 154 died during the experiment,
and 94 survived. The distribution of frontal breadths in the sur-
vivors is shown by the lower curve in the diagram, and you see
that the mean of the survivors is clearly below the mean of the
original series, the mean of the dead being above the original mean.

“Two other cases, which are only examples of a series in my
possession, show precisely the same thing.

“These experiments seemed to me to show that very finely divided
china clay does kill crabs in such a way that those in which the
frontal breadth is greatest die first, those in which it is less live
longer. The destruction is selective, and tends to lower the mean
frontal breadth of the crabs subjected to its action. It seemed to
me that the finer the particles used in the experiments, that is to
say, the more nearly they approached the fineness of the actual silt
on the beach, the more selective their action was.

“T therefore, went down to the beach, where the crabs live, and
looked at the silt there. This beach is made of moderately small
pieces of mountain limestone, which are angular and little worn
by water. The pieces of limestone are covered at low tide with
a thin layer of very fine mud, which is much finer than the china
clay I had used in my experiments, and remains suspended in
still water for some time. Under these stones the crabs live, and
the least disturbance of these stones raises a cloud of very fine
mud in the pools of water under them. By washing the stones of
the beach in a bucket of sea-water, I collected a quantity of this
very fine mud, and used it in a fresh series of experiments, precisely
as I had before used china clay, and I obtained the same result.
The mean frontal breadth of the survivors was always smaller
than the mean frontal breadth of the dead.

DARWINISM DEFENDED. 161

“T think, therefore, that Mr. Thompson’s work, and my own,
have demonstrated two facts about these crabs; the first is that
their mean frontal breadth is diminishing year by year at a measur-
able rate, which is more rapid in males than in females; the second
is that this diminution in the frontal breadth occurs in the presence
of a material, namely, fine mud, which is increasing in amount,
and which can be shown experimentally to destroy broad-fronted
crabs at a greater rate than crabs with narrower frontal margins.

“T see no shadow of reason for refusing to believe that the action
of mud upon the beach is the same as that in an experimental
aquarium; and if we believe this, I see no escape from the con-
clusion that we have here a case of Natural Selection acting with
great rapidity, because of the rapidity with which the conditions
of life are changing.”

These observations and conclusions of Professor Weldon have
been the subject of much discussion. The adverse criticism has, on
the whole, seemed to be successful in discrediting the case as an
example of any such clear-cut action of natural selection, as Weldon
seems to hold it to be. J. T. Cunningham (Natural Science, Vol.
XIV, pp. 38-45, 1899) concludes, after a critical analysis of the
work, that ‘““Weldon’s observations may be completely explained by
variations in the amount or rate of growth. The difference in
different years would be at once explained if the amount of change
in frontal breadth was constant for each moult, while the amount
of growth was variable. The fact is, that in 1893 crabs of a given
frontal breadth were larger than in 1895 and 18098; and I have
shown that the summer of 1893 was exceptionally fine and warm.
Either the warmth alone, or warmth and food together, very prob-
ably made the crabs grow more in that year for the same number
of moults. On this view the broad-fronted crabs died in the expe-
Timents with clay and mud because they were younger and weaker.
In the same way the crabs that moulted in the bottles possibly
grew more than those in the sea, because they were kept in warmer
water and supplied with more food. Therefore they were, after
the moult, larger than those in the sea of the same relative frontal
breadth.

“The change described is not, if terms are used correctly, a change
in the character of the species, but merely a change in the rate of
development. The variations investigated are not individual differ-
ences, since each individual in the course of its growth passes
through each one of the variations in its own person. It has not
been shown that the change has gone on continuously for five
years, or that it has taken place only in waters where there is much
mud. If tadpoles of the same size were found to have shorter tails

162 DARWINISM TO-DAY.

in one year than in another, few biologists would draw the con-
clusion that the result was due to the selective destruction of those
with the longest tails. The more probable explanation would be
that those with the shorter tails were in a more advanced stage
of their metamorphosis.”’

7 Plate, L., “Uber die Bedeutung,” etc., pp. 31-32, 1903.

® Tayler, J. L., “The Scope of Natural Selection,” Nat. Science,
Vol. XV, pp. 114-129, 1899.

* Morgan, C. Lloyd, “Factors in the Evolution of the Mammalia,”
Nat. Science, pp. 97-101, 1892.

° Plate, L., “Uber die Bedeutung,” etc., pp. 159-160, 1903.

1 Tayler, J. L., ‘The Scope of Natural Selection,” Nat. Science,
Vol. XV, pp. 114-129, 1899. I quote as follows: ‘In the development

Tayler's ex- of the individual we see a disappearance of structures,
planation of dee which appear to become, with advancing development,
generation by —useless, almost parallel to the gradual disappearance of
natural selection. rudiments, etc., in the history of the species evolution.
And a common explanation for both of these series of phenomena
can, I believe, be satisfactorily found in the known facts of nutrition.
Growth of any tissue would seem to depend on three conditions,
a stimulus of the part adequate to promote functional activity,
a proper food supply, and efficient removal of products produced
by that particular tissue’s activity. There is abundant evidence
to prove that a tissue tends to degenerate if its own excretory
products are not removed; the evil effects produced by fatigue
products in muscle and other tissues on the activity of the tissue
itself, prove that this factor must be of great importance where-
ever it is found to occur. Just as the growth and development of
bacteria are interfered with, and finally altogether checked by the
accumulation of products of their own activity, so a tissue in the
higher organisms has its activity impaired and its power lessened
when for some reason diminished elimination of its own metabolic
products occurs. Now both in the development of the individual
and the race we see an alteration of structure, a gradual transition
from the less to the more specialised, and in this gradual transition
there must be, as I endeavoured to prove in my answer to the last
objection, an alteration in the line of functional activity of the
parts, and that, owing to this fact, a tissue that was necessary in
the earlier stages became less and less so as specialisation advanced,
the whole tendency of the specialising organism being continually
and increasingly against the earlier, less specialised, stages. It will
thus happen that every structure which is becoming useless, owing to
its deficient specialisation, whether in the history of the race or the
individual, will have two adverse sets of conditions to contend

DARWINISM DEFENDED. 163

_with—one, defective elimination of its own tissue products, owing
to its becoming increasingly removed from the growing organismal
specialisation of food products, while secondly, for this same reason,
its own food supply will become less and less suitable. This theory
would apply equally to germinal and somatic development and
atrophy of structure; there would thus, through the alteration of
functional activity of the whole organism, be brought about elimina-
tion of all structures not in the line of evolution; and, therefore,
organismal selection alone, if this theory is sound, would be able
to explain the complete disappearance of rudiments, the various
forms of development and atrophy, without calling to its aid climatic
inheritance, panmixia, and ee or any other form of particular
Scan

* See the account of the observations of Kellogg and Bell in the
appendix of chap. iv
** Morgan, C. Lloyd, “Animal Behaviour,” p. 2609.
““ De Vries, H., “Die Mutationstheorie,” 2 vols., 1901, 1003.
** Plate, in a later briefer treatment (‘“‘Darwinismus kontra Muta-

tionstheorie,” Archiv f. Rassen- und Gesellschaft-Biologie, Vol. III,

Plate's expla- PP- 183-200, 1906) of some of the offered objections to
nation of charac- Natural selection refers to this matter from a slightly
ter fixity indo- different angle. “So sehr der Ziichter danach streben
mestic animals. muss, erblich konstante Formen zu erhalten, um der
Muhe der bestandigen Auslese enthoben zu sein, so wenig spielt dieser
Punkt in der freien Natur eine Rolle. Hier findet eine nie nachlas-
sende Zuchtwahl statt, wodurch der betreffende Charakter auf einer
gewissen Hohe erhalten und vor Riickschlag bewahrt wird. Welcher
Grad von Konstanz nun auf diesem Wege im Laufe von Tau-
senden von Generationen erzielt werden kann, ist eine zurzeit
noch ungeloste Frage, die ihrer Natur nach wohl kaum mit Sicher-
heit beantwortet werden kann. Jedoch lehrt die Tier- und Pflanzen-
zucht, dass der Rtickschlag nach dem Aufhoren der Selektion
um so spater und um so seltener eintritt, je langer und je intensiver
der Zuchtungsprozess vorher betrieben worden ist. Daraus ist zu
schliessen, dass die langandauernde Zuchtwahl, welche die Natur
ausubt, jenen relativ hohen Grad von Erblichkeit zu erzeugen
vermag, welcher den Spezies-Charakteren im allgemeinen zukommt,
denn vollig konstant sind diese bekanntlich auch nicht.”

** Tayler, J. L., “The Scope of Natural Selection,” Nat. Science,

Vol. XV, p. 119 ft, 1899.

CHAPIER WIL

DARWINISM DEFENDED (CONTINUED) : PLATE’S
CONCILIATORY DEFENCE.

THE foregoing consideration of the answers of the Dar-
winians to the objections urged against the effectiveness of
the selection theory as an explanation of evolution makes
no pretence of having included, or even referred to, all
the arguments offered by the defenders, and it is only fair
to note that by no means all Darwinians and neo-Darwin-
lans agree to making the concessions listed in the early
part of the chapter. Some refuse a certain one or
two of these concessions, some another or others, some
indeed will make no admissions at all. With these last we
are past arguing. The discussion assumes too much an “‘it
is, it isn’t” character to be particularly illuminating or pro-
gressive. But because of those who concede in considerable
measure, and deny in some measure, the validity of those
chief objections to the species-forming capacity of natural
selection, the general character of the ground on which
this last stand for the old flag is being made should at least
be indicated.

This half-surrendered but still not quite deserted position
is perhaps most clearly to be seen through the smoke of

Plate’s con- | battle by fixing one’s eyes on the representative
sideration of the foure of Ludwig Plate, a strong Darwinian,
objections to = © =
selection, but one not blinded by prejudice or with ears
wilfully closed to the calls of reason. In his recent elaborate
discussion * of Darwinism, so often already referred to and
quoted from in these present chapters, he groups under the
head of wesentliche Einwdande (important objections) the

164

DARWINISM DEFENDED. 165

attacks on the species-forming capacity of natural selection,
which are based on (1) the slightness and inutility of the
fluctuating Darwinian variations, and (2) the improbability
of the right variations appearing at the right time to make
possible the development of specialisations of qualitative

and coadaptive character. In a discussion of some length |

(pp. 32-77), mostly quite fair and unprejudiced, he brings
out the best and strongest arguments that the faithful Dar-
winians have to offer to reduce the force of at least, if not to
answer satisfactorily, even for themselves, the most effective
attacks on the capacity of selection. In very condensed form
I present in the following paragraphs the essential points
in these defensive arguments.

In regard to the first objection, namely, that the very
slight or small differences in organs and functions which

result from the fluctuating or Darwinian varia-

The objection .. ‘
to the slightness tions cannot be sufficiently advantageous or
of Darwinian = disadvantageous enough to afford “handles”
variations, ; : ‘

for natural selection, that is, cannot be of life-
and-death-determining value, Darwin devoted, in his “Origin
of Species,’ a whole chapter of discussion and argument
to show that in many cases even the slightest of differences
may conceivably (it is of course a matter practically incapa-
ble of proof by observation or experiment) be sufficient to
turn the scale, in a rigorous competition, one way or the
other. In many other cases such differences could not, even
to Darwin, appear sufficient to be of a life-and-death advan-
tage or disadvantage. But Darwin too often, Plate admits,
confounded mere usefulness * with life-and-death-deciding
usefulness (or non-usefulness).

However, for many cases Plate maintains that the slight
Darwinian variations can serve as handles for selection,
particularly in periods of unusual rigour of competition
or fierceness of struggle (either active or passive): ex-
amples are, slight differences in the speed of preyed-on

166 DARWINISM TO-DAY.

animals when pursued by an enemy, or slight differences
in the length of neck of the giraffe in time of scarcity of
foliage, or slight differences in the effectiveness of the
organs of sense at times of approaching danger, or in
endurance of cold, heat, hunger, dryness, etc., or in
the clothing of hairs or feathers, the number of capil-
laries in the skin, or richness of glandular secretion, and
the like, in times of special stress of weather. ‘“Dodel-
Port * has shown that microscopically fine hairs are capable
of keeping plant-lice away from leaves or buds, and that
very slight differences in the specific gravity of the seeds
of water-plants may determine whether these seeds sink to
the bottom and consequently germinate or not. For the long
flights of migratory birds or for birds like our house-doves
which protect themselves from birds of prey by swift flights
upward to great heights, every smallest amount of advan-
tage in the pneumaticity of the bones will be of worth and
finally of vital advantage, just as every racing bicyclist
knows by experience that for his record-breaking at-
tempts he must have a machine in which every part is
made as light as possible, for the effects of weight are cumu-
lative in course of time.” And Plate fills a couple of pages
with other similar cases. ‘‘Whoever scrutinises the life of
nature and of man with biologically trained eye sees over
and over again the coming of great effects from slight
causes. The average of accidents in factories increases in
proportion to the age of the workers, because muscular
strength and keenness of the sense organs decrease with
increasing age. In each age-class the difference is but
slight, but in spite of that it demands its sacrifice. Nageli,
in a paper concerning the abundance of tuberculosis, showed
that among 500 dead human bodies examined 97 per cent.
showed traces, at least, of tuberculosis. That is, practically
every adult human is tainted by this disease. Now how
often must slight differences in body structure, life habits,

DARWINISM DEFENDED. 167

hygienic conditions, yes, even in temperament, determine
whether there shall be healing or death? The iridescent
colours of many male birds, butterflies, and certain parasitic
copepods (Sappharina), are certainly of a nature to pro-
duce a great effect on the eye, but these colour effects are
not the result of special pigments but of microscopically
minute structural conditions. In Africa the tsetse-fly * ex-
tends over large regions, and only those cattle with a skin of
a certain thickness, so that the tiny proboscis of the fly
cannot penetrate it, can live in these regions immune from
the fatal attacks of the pest. Many poisons work in almost
infinitely weak dilution—a 1-200,000 solution of ricin, for
example, is able to kill mice.” |

Plate presents a second type of answer to the objection
by calling on certain aids or auxiliary principles by whose in-

fete fluence a difference at first unimportantly small
may aidslight gradually comes to be transformed into one of
ree: selective value, or may reach this stage sud-
denly by means of a change in life habits. This may come
about “through correlation,’ that is, through that unknown
law of growth by which an indifferent organ may be so
bound up with or related to a useful organ’ that it, the
indifferent organ, is perfected along with the useful organ
as this latter is developed or specialised through selection.
All organs of an animal are intimately related to and influ-
enced by one another: each is in relation to the other just
as to the outer world. How close this inter-dependence is,
is most easily appreciated by one in his own case when sick:
a constipation causes headache, a slight diarrhoea affects the
composition of the urine, etc. The correlation can be so
intimate and important, as the case of the secondary sexual
characters shows, that its origin and development depends
directly on particular definite stages of the related organs.”
In the case of many animals the appearance of various curi-
ous and large modifications of legs, wings, skin, feathers,

168 DARWINISM TO-DAY.

hair, etc., etc., depends on the various stages of development
reached by the reproductive organs. Now these secondary
organs or modifications thus produced through the influence
of other organs may be for a while slight and indifferent
in character, but yet safely maintained. When they reach
a stage of utility or of positive disadvantage they will then
be further perfected, or on the other hand be extinguished,
by selection.

The principle of the change of function (Functions-
wechsel) first elaborated by Dohrn,’ is also called on by

eee Plate to play an important part in explaining
ciple of change how an organ of considerable specialisation can
ac be shown to have been developed by selection,
although the function it is now performing seems to be one
that could have been useful only in a perfected state and
hence could not have made the organ so constantly ad-
vantageous in all the slow and gradual stages of its evolution
as to be of selective value in its beginning stages. Dohrn’s
principle is stated as follows: “An organ can, in its service
of a certain definite useful function, be developed by natural
selection to a certain stage. Simultaneously a second func-
tion (Functionserweiterung) can have developed, due to
some special peculiarity or condition of the position, struc-
ture, or capacity for movement, which may have a value in
another direction from that of the first function. Thus
the appendages of crabs serve often special functions in rela-
tion to respiration, copulation, and care of the eggs or
young, while their original locomotory function may still
be maintained or may be more and more surrendered in
favour of the new functions.” Numerous other specific ex-
amples are obvious enough to any student of biology. Now
the new functions in many cases become the more import-
ant so that there in time results a complete change of func-
tion which wholly alters the physiological character of the
organ, and in many cases it is difficult to see (if one does

DARWINISM DEFENDED. 169

not know the phyletic history of the organ and the
function) just how selection could have developed such an
organ by slow degrees from slight beginnings. But the
secret of the explanation, which is a perfectly consistent
Darwinian explanation, lies in the Functionswechsel phe-
nomenon.

“Indifferent characters can suddenly become of selective
value through change of environmental conditions or of
life-habits. The cranial sutures are certainly of no vital
importance with the reptiles and birds, but they can be of
very great importance to the viviparous mammals as adapta-
tions for passing the pelvis during birth. Lacerta vivipara
has, perhaps, no advantage through its viviparousness over
its nearly related species in our country, but in Scandinavia
it has to thank this peculiarity alone for its success in life,
because the development of its young is rendered inde-
pendent of the sun by it. The nectaries were probably at
first useless to the flowers; from that moment, however,
when the insects learned to know them as food reservoirs
and unwittingly insured cross-pollination by their visits to
them, they became of the greatest importance and the indi-
rect cause of the origin of the colour brilliance of the
flowers.

“There are organs of universal character which can be-
come modified in most widely differing directions. Thus
the tail of the mammals, originally a long, evenly-haired
organ, can, without going through any very elaborate
changes, be modified into a bushy steering-rudder of special
use in climbing from branch to branch; or by the outgrowth
of a terminal tuft be changed into a flying fan; or by the par-
tial loss of the hair become a grasping organ, or a balancing
organ, or an aid in leaping, a rudder in swimming, or a cover
against rain and cold (Myrmecophaga jubata). The append-
ages of crabs, the cirri of the annelids, and the teeth of mam-
mals are further examples of a similar plasticity and capacity

170 DARWINISM TO-DAY.

for modification in the most manifold ways, in which the
first stages are often of immediate use.”
Following these suggestions as to the aid that selection
may have from various helping conditions to make its
:; starts, Plate discusses as further similarly help-
Fe soles ful conditions or auxiliary principles three most
herited results important matters, namely, the effects of con-
of use, from or- : 1a
thogenesisand tinued use on parts, the principle of orthogen-
oe esis, and the facts of sudden discontinuous
variation. But as these three categories of
biological phenomena and principles are exactly those,
among others, which anti-Darwinians hold to be not aids
to the selection theories, but to be the basis if not of actually
replacing or substitutionary theories, at least of precisely
those objections to the species-forming capacity of the strict
Darwinian factors which have necessitated some of the
principal concessions made by the Darwinists, it is obvious
that Plate’s discussion of them is in itself simply the actual
making of the concessions already noted as having been
admitted by most Darwinians. Each of these categories
of phenomena and principles is of course of much import-
ance and interest, and they will all be found to be fairly fully
set out in the chapters following this one.
Plate’s answers to the second important objection, namely,
that selection relies too much on chance and is therefore
ae, improbable and inexact, may now be noted. He
the objection | distinguishes two phases of this objection. The
oe the first he expresses as follows: “It is highly im-
ependence of
selection on probable that for the progressive development
erat or perfecting of an organ there will always
appear just at the needed time the variation necessary for
selection, that is, the exactly needed adaptive modification.”
The second phase is: “It is highly improbable that in the
development of a complicated organ, or body-part, or in
the perfecting of a changing adaptation the numerous indis-

. DARWINISM DEFENDED. 171

pensable modifications will appear in such a series that a
harmonious correlation of the single variations will be
possible.” :

Referring especially to the first phase of the general ob-
jection he says:

“Thus this doubting query is, why do there always appear
just the right variations at the right time? Or, somewhat
differently expressed, in the words of Cope,’ ‘since the
number of variations possible to the organism is very great,
the probability of the admirably adaptive structures which
characterise the latter having arisen by chance is extremely
small.’

“Whoever expresses such doubts unwittingly hitches the
wagon before the horse. Selection directs itself according

to the variation, not variation according to
Selection fol- , partes , ‘
lows variation, Selection. If the variability is large, selection
not variatio has a large choice; if the variability is small,
selection, : ;

then there are but few lines of evolution open.
Experience teaches that in general, the variability of organ-
isms is very large, that it occurs both quantitatively and
qualitatively in such pronounced manner in all individuals
of a species that it can be readily recognised without re-
course to complex methods of investigation, and that no
characteristic (size, form, colour, numerical relation, consti-
tutional vigour, instinct, life-habit) is free from it in any
life stage from egg to last drawing of the breath. It is
precisely to this variability expressing itself in the most
manifold ways and combinations that is to be ascribed the
condition that any individual as such is, usually, readily
to be distinguished from other individuals of the same
species. It results from this that the individual variation is
indeterminate and undirected, or better expressed, universal
and all sided, and that at any given moment the exactly
needed modification will always appear in a number of indi-
viduals of any species rich in individuals, provided that

172 DARWINISM TO-DAY.

the needed variation can be produced through a slight ad-
vance or progressive change. Naturally it is not sufficient
if the variation appears in only a few isolated individuals,
but it is necessary, for the modification of the species, that
this variation occur in so many individuals that it will not
be extinguished through interbreeding but on the contrary
will be perpetuated. In other words selection works, except
biiestiac wake in scattered cases where single or ics varia-
with plural vari- tions are specially favoured by accidental iso-
caine lation, not with single but with plural variations
or varieties. Through this the host of variations is im-
mensely reduced as far as they come into consideration as.
handles for selection, and of course only in this sense is
there any reason at all for the query as to whether we can
assume that the right variation will always be present at the
right time. The answer can only be, certainly not always:
many promising beginnings must always be checked in the
germ or at half-way, but in infinitely many cases the needed
plural variation will appear, because the same external
factors change a whole group of animals simultaneously
so that progress is possible. But, it goes without saying,
only a slow advance is conceivable on this basis.
“One must not, for the rest, forget that the same condi-
tion of selective worth may be reached simultaneously
_ through combinations of different peculiarities,
calyg may ead that the same effect may be attained by
attained in dif’ various means, both of which facts render it
ferent ways. ; : ‘ 5
importantly easier to get this selective worth.
When pursued by an enemy one individual of the harassed
species may save itself by a quick leap, a second through
sharp ears, a third by sharp eyes. Wallace rightly explains
that the necessity for a giraffe in times of famine is only to
reach as high as possible in the trees, and that different
means may avail for this, as a longer neck, long legs, or a
long tongue, all of which may eventually come to be correl-

DARWINISM DEFENDED. 773

atively increased. The individuals which survive by these
aids may then later, through inter-crossing, exchange their
advantages and so lead to the production of a mean type
that shows a slight advance over earlier conditions in all
three organs. Mammals can protect themselves from flies
in various ways, either by a thick fur (bears), by reflexive

twitchings of the skin muscles (horse), by tails with tufted

ends (many hoofed animals), by a long neck which can bend
sideways so that the animal can reach any part of its body
as far as the hips (guanaco, stag) or finally by eyelids and
long movable ears, which restrain the flies from the easily
injured eyes. These means of protection from insects play
an important role in determining the habitus of many mam-
mals, and permit the conclusion that selection has been
instrumental in producing this habitus. Here, also, it is

possible for several of these means to be possessed at once

by the same animal, as in the case of the guanaco with its

long hair and elongate neck. It is absolutely necessary for

molluscs that live between tide-lines to have some means of

resisting the force of the surf. Many species possess this
means in their small size which allows them to crawl into

crevices and cracks in the rocks, but most of them have

developed a strong pedal sucker and a low roof-like uncoiled

shell which presses close to the rock surface and over which

the water flows without exerting any strong lateral pres-

sure. This is the case, for example, with Patella, Fissurella,

‘Chiton, Concholepas, Siphonaria, Gadinia, Calyptra, and

others. All three of these means of safety can come into
play simultaneously in selection, but it suffices when any
given individual possesses any one of these means in suffi-

cient degree of development.

“T shall note here several other examples which show

how related species reach the same advantage in the strug-
gle through different means, for we can assume from these
facts that also the individuals of the same species often

174 DARWINISM TO-DAY.

escape the same dangers in the struggle for existence by
means of different means. And by this the probability is
made greater that the ‘needed variation’ appears at the
right time. The differing characteristics of this sort will
later lead, through crossing, to the formation of a mixed
type, or, if the competition grows ever sharper with the
course of time, they will produce a separation of the species
into varieties (eventually species) with differing habits of
life, or finally they may meet in direct competition or strug-
gle with one another. The good flyers among the birds all
have long wings, but in some it is the fore arm which is
specially lengthened (cuckoo, goat-sucker, pigeon), in others
the hand (terns, humming-birds, eave swallows), and in
still others the upper arm (swan).—While Tapirus ameri-
canus, like most mammals, drives the flies away from its
eyes by throwing down the eyelids, Tapirus indicus accom-
plishes the same thing by a strong rotation of the bulb of
the eye. Elephas africanus seizes very small objects with
its proboscis-fingers, while the Indian elephant lays the front
end of the trunk laterally on the ground, grasps the object
between the skin-folds, lifts it up high in this way, and
only then allows it to fall into the tip of the proboscis.—
Poulton has shown by several examples that in cases of
mimicry the same effects may be got in very different ways.
The glass-like transparency of the wings, for example, is got
in the Heliconid genus Menthona by a considerable dimi-
nution in size of the scales, in the Danaid /tuna thona through
the absence of most of the scales, in Castnia linus var. heli-
conoides, through the absence of pigment in the scales, which
are as large and numerous as usual, in the Pierid Dismor-
phia crise through the smallness of the scales, and finally in —
the night moth Hyelosia heliconoides by the absence of pig-
ment and lessened number of the scales.”

Plate next offers a detailed explanation on strict Darwin-
ian grounds of how such an extraordinary condition of

DARWINISM DEFENDED. 175

mimicry can be brought about as the famous case of Kal-
lima, the butterfly that simulates in colour, shape, and inti-

mate details of pattern such as veins, flecks,
ee of fungus spots, etc., a dead leaf with such fidelity

as to make it the wonder of every one who sees.
it and the classic example of the possibilities of such protect-
ive resemblance. And he shows well that whatever diffi-
culties selection may have in its necessary dependence on
the chance occurrence of the proper numerous and neces-
sarily simultaneously appearing variations to explain the
gradual development of such a specialisation, the only other
explanations so far offered are even more ludicrously de-
pendent on “luck.” Piepers,’ the most active and polem-
ically vigorous of all special opponents of the Darwinian
explanation of protective resemblance and mimicry, says:
“Chance alone can bring about such a correlation.” As
Plate well says, “It is not without its comic aspect that a
violent antagonist of the selection theory should be found
clinging to the same safety-anchor ‘chance,’ that usually
is the constant reproach of the Darwinian. . . . It would not
be difficult,” continues Plate, “to refer to still other examples.
to show that a needed selective value can often be attained
at the same time by the individuals of a species through
various means, by which the probability that this type of
adaptations can arise is correspondingly increased. But
one point should never be forgotten and that is it is always
first the variability, and second the selection. If no varia-
tions appear there can be no progress, and if the struggle
for existence were too severe the [non-varying] species.
would die out. Strictly speaking, the question, how is it
possible that the right variations can be relied on to ap-
pear at the right time? is really inverted and therefore
incapable of receiving a correct answer. One can only
say: If a complex adaptation has arisen through selec-
tion, then it is certain that the necessary modifications.

176 DARWINISM TO-DAY.

needed for success in the struggle for existence were not
wanting.”
We come now to the second phase of the general objec-
tion, as analysed by Plate; viz., the assumed improbability
that during the course of the development
Caines (evolution) of a complicated organ or whole
ability ofthe | body-part, or during the perfecting of a chan-
ne fos al ging adaptation, the numerous necessary varia-
tions neededin tions will occur in such a successive series as
seaiieee el to make possible an harmonious correlation of
structures,
the various single variations. Plate writes as
follows: “This objection has been, as is the case with the
objection just discussed, raised by many students of evolu-
tion as Spencer, Wigand, Nageli, and is in principle not
different from the previous objection, but only presents an
elaboration of it. It concerns, first, the numerous single
variations which are necessary if a single complex organ (as
an eye) or a whole body-part with its various organs and
tissues (for example, the neck of the giraffe, the fore body
of the elk) of a single individual is to be raised to a higher
stage of adaptiveness; and, second, the perfecting of inter-
dependent adaptations in different individuals. As example
of the latter category I may mention the corolla of flowers
and the proboscis of insects which cross-pollinate these
flowers, the male and female copulating organs of many
animals, as those of the Papilionide, the adaptations of
myrmecophilous and termitophilous animals in relation to
their hosts, also those of symbiotic (parasitic or mutualistic)
species relative to their companions, and, in cases of mimicry,
of the mimicking species relative to the protected species.
When one of the species, party to such a mutual adaptation,
changes, the other as a rule must also. There arises from
this the query : how, in such cases, is there possible the neces-
sary coadaptation (coordination), that is, the harmonious
change of the parts which produce the interdependent physi-

DARWINISM DEFENDED. © 177

ological or biological phenomena, whether these exist in a
single individual or in two? How does it come that when
the antlers of the giant stag become larger and larger, the
skull bones become thicker and the neck tendons and the
fore legs stronger (Spencer)? With the gradual lengthen-
ing of the giraffe’s neck the skeletal system and with it
numerous other closely-related internal organs have to be-
come larger simultaneously. Hundreds of small modifica-
tions are necessary. How does it happen that all come off
exactly as is necessary? When the flowers’ cups for any
reason become deeper the insects must develop longer
proboscides in order to reach the nectaries in the bottom of
the cup. Simultaneously the sucking apparatus of the
cesophagus must change. How does it happen that these
modifications in two different organisms, in an animal and a
plant, occur pari passu?

“In order to satisfy these questions of doubt Darwin and
Wallace have referred to the domesticated animals as the
best proofs that such coadaptations are possible. A grey-
hound, a bulldog, a dachshund, a tumbler pigeon, a race-
horse, have had to pass through a long series of numerous
changes in the most various organs, in order to reach their
present form, and yet all these variations have appeared
one after the other in such a way as never to endanger the
vital vigour, for man would never have chosen weakly ani-
mals for breeding purposes. In artificial selection, there-
fore, coadaptations are possible in almost infinite variety,
and it can fairly be asked if such favourable conditions are
not also possible in nature. This query must, a priori, be
answered in the affirmative, for man is not able either to
make more easy or to hasten the appearance of coadapta-
tions: he can only hold on to those which once appear, and
this can also be done by the struggle for existence in those
cases in which the coadaptive variations are of vital import-
ance. The real difference lies, therefore, in the fact that

178 DARWINISM TO-DAY.

’ man can make a beginning with ever so slight an advance;
nature only with such simultaneous changes as are of suffi-
cient grade or degree to be of selective value. And so far
in this discussion nothing has been offered to show how this
condition is to be reached.” .

To attempt to get at an explanation of the actual means
by which this necessary condition is attained, Plate believes it

Plate's belief eCeSSary that one should make clear just what
in the possibility standpoint he takes on the vexed problem of
of the inheri- : : . ;
tance of acquired the inheritance of acquired characters. With-
characters: out going into Plate’s long discussion of this old
subject, it is sufficient to say that he reaches the conclusion
that the inheritance of acquired characters is not proved
not to be possible, and hence that it may occur. And, for
himself, he expresses the belief that acquired somatic char-
acters can be and are inherited. From this point of view, he,
consistently with Darwin’s own position, finds an answer to
the objection touching the necessity of a repetitive cumulat-
ing appearance of certain definite kinds of variation for the
basis of the development of coadaptation, by invoking the
Lamarckian factor of the inheritance of the effects of use
and functional stimuli. Which refuge is of course not open
to the modern strict selectionists, the neo-Darwinians.

Now, as may be imagined, when the Darwinians them-
selves are of various minds about the value of the answers
to this objection, when these answers are based on a strict
selection basis, they are not very convincing to anti-Darwin-
ians. In general they rest on various observed facts and
deduced assumptions which may be roughly classified into
several groups. First, the facts of simultaneous correlative
variation, or the fact that organs or parts which function
together, very often vary in the same general direction. For
example, if two leg or arm bones become longer the muscles
attaching to these bones also become longer (since the
attachments are not changed). The supplying blood-vessels

‘oi
%

DARWINISM DEFENDED. 179

and nerves also lengthen. Numerous observations by
breeders show that in each organism there resides a capacity
of self-regulation, up to a certain degree, which produces a
harmonious growth and variation of inter-dependent parts.
If a plant is removed to richly fertilised soil it will grow to
great size, in the course of which growth all parts are pro-
portionally changed so that the general habitus of the plant
remains the same. If one allows insect larve to live on very
short food rations, the adult insects will be unusually small
but with all the organs of their usual relation to each other
as to proportional size. Thus it seems that the single organs
are definitely correlated with one another so that in their
growth they maintain their relative characteristics. “I
have,” says Plate, “called this form of organic Zweckmdassig-
keit the unity of organisation.” If this quality or capacity
is lacking in an individual then it develops into a cripple, a
monster, and is killed out by selection. Therefore, if the
neck of the giraffe varies so as to be longer, one may fairly
assume that, in the case of many individuals, at least, all
parts of the neck will share in this variation, although there
will naturally be slight individual varyings inside of this
general variation. And if the antlers of the stag vary
towards a larger size there will simultaneously appear the
necessary increase in calcareous materials for all parts of
the skull, so that the whole skull will be correspondingly
heavier and stronger.

“The process of evolution may be assumed to be, as it was —
by Darwin, very slow, so that plenty of time is allowed to
selection to produce the necessary coadaptations which may
be wanting in the earlier stages of the development. In
the case of the enlarging of the stag’s antlers there may have
been wanting at first the necessary congenital strengthen-
ing of the neck muscles but this would come to exist through
use. The effects of use would increase, however, only to a
certain point, and there would finally come a time when the

180 DARWINISM TO-DAY.

heavy antlers could be supported only by those individuals
which had received a strengthening of the neck muscles
through congenital variation. All others would be killed out.
“The already discussed principle. of the attainment of
selective value for a certain advantage by various means,
comes also into play in this connection. In time of drouth it
is important to the giraffe only that it can reach a certain
height on the trees; whether this height be reached by the
aid of a longer neck or higher shoulders or a specially
elongate tongue is indifferent. Through inter-breeding
these various advantages may be later united. There is
always resulting, as Wallace *” has said, ‘Selection of the
capacities or qualities resulting from the infinitely varied
combination of variations that are always occurring.’
“Recently Weismann ‘’ has presented the principle of
germinal selection as explaining coadaptive specialisations,
Plate'sdis- SO that he is evidently not satisfied with the
beliefin Weis- sufficiency of the three aiding explanations
mann’s principle ; , ¢ 5 wees
of germinal already given. I hold this germinal selection,
selection. says Plate, ‘to be a false conception, and there-
fore do not here refer to it further. It will be discussed in
detail later.”’ (This later discussion of Plate’s is a detailed
and effective destructive criticism of the theory.)
“Weismann, in his ‘Lectures on the Theory of Descent,
outlines in detail his theory, proposed several years before,
Reena that amphimixis (bisexual parentage) is so
principle of widely prevalent in both the plant and animal
amphimixis, kingdoms, because it serves as the spring of
individual variations. A considerable part of the chromo-
somes of the egg-cell is removed by the discharge of the
polar bodies, and the same results from the reduction divi-
sions of the sperm-cells. By this the possibility is created
of producing, through the fusion of the germ-cells, very
various combinations of the hereditary tendencies and, there-
fore, an actual high degree of variability in the offspring.

912

DARWINISM DEFENDED. 18t

‘Because in each reducing division of the germ-cells their
ids are lessened by one-half, the possibility exists of gradu-
ally removing from the germ-plasm of the species the ids of
the disadvantageous variations, for in each generation the
offspring of the disadvantageous id combinations are ex-
tinguished [by selection], so that from generation to gen-
eration the germ-plasm gradually becomes purified of the
disadvantageous ids, while the favourable combinations
which amphimixis produces are retained, and there finally
remain only the advantageously varying combinations or, at
any rate, those in which the advantageously varying deter-
minants are in the majority and therefore have the most
influence’ (Vol. II, p. 222). This conception of the sig-
nificance of the reduction divisions of the maturing germ-
cells and their fusion is very suggestive, and, theoretically,
there is little to be objected to in the idea that the differences
thus created can be used by personal selection for the pro-
duction of harmonious coadaptations. Indeed, with this
explanation in hand, it is obvious that the theory of germinal
selection is superfluous for the explanation of coadaptations
if we may assume that there is always a great mass of
material in the individual variations, for the possibility of
varying combinations of these requires no further expla-
nation.”

For the most part it is obvious that Plate, and with
him other fair-minded Darwinians, recognise fully the

Plate recog- COSeNcy of the objections against Darwinism
nises the weight based on the inutility of slight variations, on
of certain objec- ;
4 pia toe occurrence’ and persistence. of hosts of
ism. trivial or indifferent species differences, and
on the difficulties presented by the demands of a controlled
appearance of variations necessary to the development of
coadaptive structures and functions, so that they are inclined
to make the concessions which I have referred to in the
beginning (chapter vi) of this presentation of “Darwinism

182 DARWINISM TO-DAY.

Defended.” With these concessions made it is necessary to
call to the aid of the selection theory, if it is still to be con-
sidered an important factor in species-forming—these con-
cessions do not, of course, invalidate the claims of selection
to be the all-important final factor in determining the
general course of evolution, by encouraging or restraining
the various general lines of descent—certain auxiliary and
aiding theories or explanations. Such helps to selection are
to be found especially in isolation, organic selection, and
the Weismannian theories of panmixia and germinal selec-
tion. The outlining of these theories will form the con-
tents of our next chapter.

APPENDIX.

1 Plate, Ludwig, “Uber die Bedeutung der Darwin’schen Selec-
tionsprinzip,’ 1903.

> The question, what is meant by “selective value,” has been dis-
cussed by Conn (“Method of Evolution,” pp. 83-86, 1900), as fol-

Conn’s discus- lows: “How useful must a character be to be of
sion of selective selective value? Such a question it is, of course, im-
value, possible to answer. The preservation of any particu-
lar character is not an isolated matter. It is not single characters
that are preserved, but a combination of many characters together.
The survivor is the animal showing the best combination of char-
acters. It may even have some harmful ones, provided the useful
ones predominate. The rattle of the rattlesnake has at times doubt-
less been of a disadvantage to its possessor, and has caused the
death of hundreds of thousands of individuals. It is doubtless
possible to show, as Darwin did, that it has also been of value to
the animals. But how are we to decide whether its use or dis-
advantage is the greater, except by the theoretical conclusion that
it must on the whole be useful or it would have been eliminated?
The whole study of utility is sure to result in an unsatisfactory
circular logic, something as follows: The survival of the fittest. is
a law. If an organ be not useful it could not have been developed
by natural selection. Therefore, all organs and all characters must
be useful. Since in such a problem no one can prove a negative,
this position cannot be disproved; but it is certainly not very satis-
factory.

——

DARWINISM DEFENDED. 183

“But with all this criticism of utility it must be recognised that
the agency of utility as determining survival is becoming more
significant as discussion proceeds. We have seen that it must be
admitted that all characters to be affected by the principle of
survival, must have selective value: 7. ¢., must affect the matter of
life and death. But this demand does not prove to be so serious
when we recognise that natural selection works upon general
averages rather than individuals. Those who find the selection
principle such a great factor insist that all characters have selective
value if they have any value at all. If a character has the value
of even rendering its possessor a little more comfortable, they tell
us it will eventually be subject to the principle of survival at the
expense of non-favoured animals. The substitution of old types
by new ones is not a matter of a single generation, but many
generations. In such a long history there must be innumerable
conditions where any character, even the slightest, may have been
of use enough to give its possessors an advantage over others. It
is not necessary to believe that a character should preserve its
possessor, while all non-favoured individuals perish, in order to
consider that the character has selective value. Considering that
the origin of species is a matter extending over hundreds of years
and many generations, even little things will count in the long run.
If an animal has a slight advantage over another, which simply
gives it more comfort and enables it to obtain its food with a little
less exertion, this may tell permanently in the struggle, since such
an individual will have more energy to put into reproduction, and
hence may leave a larger number of offspring. The other non-
favoured individuals may not, indeed, be exterminated without off-
spring, but may simply produce less offspring. In this struggle for
permanency, the individuals which have the largest number of
offspring, other things being equal, will inevitably come out ahead,
and the others in time disappear.

“An example will make this clearer. A difference of an inch or
two in the length of a cow’s tail seems a matter decidedly too
small to base the selection principle upon. Can it be imagined
that the lengthening of the tail by a couple of inches can be of
selective value? Can we honestly believe that these two inches will
determine that the longer-tailed cow will live and produce off-
spring, while the shorter-tailed individuals will die? Only thus,
however, can we assume that the tail has been developed by natural
selection. Now this example, which seems to be an extreme case
of slight utility, may show us how it is possible, upon the principle
of the selection of averages, to conceive that characters of slight
use may be preserved by natural selection. It is not necessary to

184 DARWINISM TO-DAY.

suppose that the long-tailed individuals are preserved by this extra
couple of inches at the expense of the shorter-tailed individuals
in order that the character may be within the reach of natural
selection. If the animals are troubled by insect pests, it is cer-
tainly a matter of convenience to them to have a tail long enough
to brush off the flies, and the longer tail, within certain limits, will
be more useful than a shorter one. It is not likely that this will
preserve the life of a single individual, but it will follow that the
animals with longer tails will be less irritated by insects than
those with shorter tails. Now, although this would not affect the
matter of life and death, a nervous irritation would pretty surely
interfere with the reproductive efficiency. An animal that is con-
stantly bothered by insects will have less nervous energy to devote
to reproduction, and, therefore, such a constantly irritated animal
would be likely to be somewhat less prolific than one less irritated.
From this it would follow that the half of the animals with tails a
little longer than the average, would be pretty sure to leave a some-
what larger number of offspring than the half whose tails were
below the average. But a slightly increased fertility of this sort
would, in the course of a few generations, see the long-tailed animals
becoming more and more numerous, until they would eventually
replace the others.”

* Dodel-Port, A., ‘“Wesen und Begriindung der Abstammungs-
und Zuchtwahl-Theorie in zwei gemeinverstandlichen Vortragen,”
1877.

*The tsetse-fly (Glossina sp.), long notorious as a terrible
pest of cattle in Africa, produces its ravages by disseminating
(through biting, % ¢., puncturing the skin) the specific causes
(certain minute blood-inhabiting parasitic one-celled animals
known as trypanosomes) of the plague called Nagana (fly dis-
ease).

° For an elaborate discussion of the principle of correlation (not
bearing perhaps except in a general way on the point just at issue,

References to but of much general interest) see Radl, Em., “Uber
papers on corre- die Bedeutung des Prinzips von der Korrelation in
lation, der Biologie,’ Biol. Centralbl., Vol. XXI, pp. 4or-
416, 490-496, 550-560, 605-621, 1901. See also Webber, H. J., ‘“Cor-
relation of Characters in Plant-Breeding,” Proc. Amer. Breeders’
Assoc., Vol. II, pp. 73-83, 1906.

* For examples see R. Meldola, “The Utility of Specific Char-
acters and Physiological Correlation,’ Proc. Ent. Soc., London, pp.
62-92, 1896; also A. R. Wallace, “The Problem of Utility; are
specific characters always or generally useful?” Jour. Linn. Soc.,
Vol. XXV, pp. 481-496, 1894.

DARWINISM DEFENDED. 185

* Dohrn, Anton, “Der Ursprung der Wirbeltiere umd das Princip
des Functionswechsel,” 1875.

®*Cope, E. D., “The Energy of Evolution,’ Amer. Nat., Vol.
XXVIII, p. 205, 1894. I quote the following: ‘In considering the

rials proct dynamics of organic evolution, it will be convenient
chat diataral to commence by considering the claims of natural
selection cannot selection to include the energy which underlies the
make new char- process. That natural selection cannot be the cause
— of the origin of new characters, or variation, was
asserted by Darwin,* and this opinion is supported by the following
weighty considerations.

“(1) A selection cannot be the cause of those alternatives from
which it selects. The alternatives must be presented before the
selection can commence.

““(2) Since the number of variations possible to organisms is
very great, the probability of the admirably adaptive structures
which characterise the latter having arisen by chance is extremely
small.

“(3) In order that a variation of structure shall survive, it is
necessary that it shall appear simultaneously in two individuals of
opposite sex. But if the chance of its appearing in one individual
is very small, the chance of its appearing in two individuals is
very much smaller. But even this concurrence of chances would
not be sufficient to secure its survival, since it would be immediately
bred out by the immensely preponderant number of individuals
which should not possess the variation.

“(q4) Finally, the characters which define the organic types, so
far as they are disclosed by paleontology, have commenced as
minute buds or rudiments, of no value whatsoever in the struggle
for existence. Natural selection can only effect the survival of
characters when they have attained some functional value.

“In order to secure the survival of a new character. that is, of
a new type of organism, it is necessary that the variation should
appear in a large number of individuals coincidentally and_ suc-
cessively. It is exceedingly probable that that is what has occurred
in past geologic ages. We are thus led to look for a cause which
affects equally many individuals at the same time, and continuously.
Such causes are found in the changing physical conditions that have
succeeded each other in the past history of our planet, and the
changes of organic function necessarily produced thereby.”

° Piepers, M. C., ““Thesen tiber Mimikry,” Verh. Internat. Zool.
Cong., p. 350, 1902.

* “Origin of Species,” ed. 1872, p. 65.

186 DARWINISM TO-DAY.

* Wallace, A. R., “Are Individually Acquired Characters Inher-
ited?” Fortnightly Review, Vol. LIII, pp. 490-498, 1893.

11 Weismann, A., “Uber Germinal-Selection,’ Verh. Internat.
Zool. Cong., 1896.

*? Weismann, A., ‘““Vortrage tiber Descendenztheorie,” 2 vols., 1902.

ya 1
ay oy dx oe
(

CHAPTER VIII.

OTHER THEORIES OF SPECIES-FORMING AND
DESCENT: THEORIES AUXILIARY TO SELEC-
TION.

To be considered now are two categories of (mostly)
post-Darwinian theories, viz., those which have been offered

Classification 29 alternative theories intended to replace more
of other theories or less nearly entirely the selection theories,
aie and those other theories intended to serve as
selection. auxiliary and supporting theories for Darwin-
ism. Obviously these two kinds of theories * emanate from
the two opposing biological camps. Several of these alter-
native and auxiliary theories of species-forming have been
referred to incidentally in the preceding two chapters, for
the replacing theories constitute part of the strength of
the anti-Darwinians, while the supporting theories are dis-
tinctly relied on to help maintain the Darwinian front. The
present chapter, then, is mostly a continuation of the pres-
entation of “Darwinism Attacked” and “Darwinism De-
fended,” which is given a separate place because of the
special character of the argument with which it has directly
to do, namely, the synthetic or theory-building side, instead
of the analytic or theory-destroying side, and because of
the probable advantage to the student and general reader
wishing to understand and compare the general character
and significance of the various new theories of species-
forming with whose names, such as heterogenesis, ortho-
genesis, metakinesis, geographic isolation, biologic isolation,
organic selection, or orthoplasy, he occasionally meets in his

187

188 DARWINISM TO-DAY.

general reading. As directly continuing the last chapter we
may consider first those theories put forward, chiefly by
Darwinians, as auxiliaries or supports of the selection
theory. Then we may briefly take up those theories that
have been advanced, mostly in recent years, as more or less
nearly completely prepared to replace Darwinism as a suff-
cient scientific causo-mechanical explanation of species-
. forming and descent.

The Weismannian Theories of Panmixia and Germinal
Selection..—Weismann has for years been the most con-

Weismann's im. SPCUOUS of the neo-Darwinians, that is, of
portant contribu. those who would free Darwinism from all taint
tions to biclogy. Gf Tamarckism—it should always be remem-
bered that Darwin was inclined to attribute some degree of
influence in species-forming to the Lamarckian factor of
the inheritance of individually acquired adaptive charac-
ters—and to make selection the all-sufficient and, indeed,
sole factor in species-forming. His great services to biology
in general and to the clearer understanding of the problems
of heredity and descent in particular, are unquestioned and
unquestionable. His careful investigation and illumination
of the vexed question of the inheritance of acquired charac-
ters, his definitive exposition of that point of view which
distinguishes sharply in the individual between the germ-
plasm (that particular protoplasm in the body from which
the germ-cells, eventually new individuals, arise) and the
soma-plasm (that which develops into, or gives rise to, the
rest of the body), his development of the interesting and
suggestive combinations of fact and theory designated by
the phrase names “continuity of the germ-plasm” and “im-
mortality of the Infusoria,’—these products of his investi-
gating and philosophising mind prove him one of the ablest
of modern biological scholars. They also make him the
principal present-day champion of the selection theory. For
all these expositions of fact and theory are of a nature to

“:

OTHER THEORIES OF SPECIES-FORMING. 189

enhance the credit of selection and to discredit certain other
species-forming theories, in particular the only one, namely,

ee Lamarckism, which, until recently, has been in
champion of any real sense a rival of Darwinism. Against
eaeceians Weismann then and against Weismann’s re-
modelled kind of Darwinism, against his propaganda of the
Allmacht of selection, the adherents of Lamarckism and the
critics of selection have turned their sharpest weapons. The
result of the struggle has been to compel Weismann himself
to say: “Although the principle of selection appears to solve
in simplest manner the riddle of the fitness (Zweckmassig-
keit) of all arising organisms (alles Entstehenden), yet it
appears ever more clearly in the course of the further inves-
tigation of the problem, that one cannot explain all with it,
at least in its original limitations (dass man mut ihm, in
seimer wurspriingliche Beschrankung, wenigstens, micht
ausreicht).”

To support the selection theory in two of its weakest and
most criticised places, Weismann has proposed two striking
auxiliary theories, namely, the Theory of Panmixia, to
explain the degeneration of functions and organs, and the
more recent Theory of Germinal Selection, to account
for the now practically generally admitted existence of
orthogenesis or determinate variation and evolutionary
progress along fixed lines even to the possible final dis-
advantage of the organisms involved, and to account for
the beginnings of variation and their maintenance until
sufficiently developed to serve as handles for selection. The
proposal by Weismann of the second theory, that of
germinal selection, was the practical admission on his part
of the impotence of selection to initiate new lines of develop-
ment or descent. It was a concesston on Weismann’s part
of the justness of the demand for ati evolutionary factor to
explain the beginnings of lines of development, whether of
new organs or new species. And there is no doubt that it is

190 DARWINISM TO-DAY.

the most ingenious mechanical explanation yet offered of
the workings of such a factor. Indeed, Weismann, with
characteristic ingenuity and capacity, has offered the be-
lievers in orthogenesis that which they so far had not been
able to get for themselves, namely, a possible causo-mechan-
ical explanation of it. It should be noted that Roux’s theory
of the battle of the parts (explained later) was a forerunner
of, and undoubtedly the suggestion for, the theory of
germinal selection.
Familiar to all students of biology, and certainly not
wholly unfamiliar to laymen, are those structures or parts
in the body known variously as vestigial struc-
Riis _ tures, rudimentary or degenerate organs. The
plain vestigial vermiform appendix in man is one; the eye of
oor the mole is another; the functionless wing of
the ostrich, the useless fore-feet of a milk-weed butterfly,
and the splint bones of the horse, are others. Almost every
animal kind possesses vestigial organs, and some kinds
possess very many. Those in the human body make an
amazingly long list. All these are organs, which have once—
that is, in ancestors of the present particular organism
—been well-developed and probably useful. But these
organs now are useless or even harmful. The human
appendix vermiformis is harmful; the tiny fore-feet of the
milk-weed butterfly are useless. Why do animals have
such vestigial organs? Because they derive them by hered-
ity from ancestors. But in these ancestors the organs were
well developed and useful. How is it that the present
organisms do not need the same organs? They have adopted
new habits, or live in a new environment, or have developed
other means of supplying the old want; in a word the organs
are superfluous. How is it that the organs have become
thus degenerate or vestigial? This is the question that
selection has difficulty in answering satisfactorily. Selec-
tion can develop and specialise organs of use and advantage;

OTHER THEORIES OF SPECIES-FORMING. Igt

but how can it cause organs no longer useful and advan-
tageous to degenerate?

It is possible, perhaps, to explain the eradication of
positively harmful organs by a process of negative or
reversed selection. If an organ becomes actually harm-
ful because of a change in life conditions, individuals.
with the organ in poorest, least energetically functioning
condition might be conceived to have an advantage and be
preserved by selection to pass on to their offspring this
less developed, i. e., rudimentary or vestigial, character of
the particular organ in question. But when the organ is
simply only rendered useless by the change in life condi-
tions, as when a species of fish or insect gradually comes to:
inhabit. deep dark caves and thus has no more use for its
eyes, how does selection explain the degeneration? It really
doesn’t, satisfactorily. So Weismann offers the theory of
panmixia to account for it. This is, simply, that owing to.
the cessation of selection in regard to the particular organ
whose function is rendered no longer advantageous or
necessary under the new life conditions—that this cessation
of selection is an obvious result of such a state of affairs
was recognised by Darwin himself, and by other biologists—
individuals born with this organ defective or in a condition
below the average, would not be necessarily killed by the
rigours of the intra-specific struggle, and would therefore be
as likely to mate and keep on producing offspring as the
ones with the organ in average or above average conditions.
This general participation of all kinds of individuals (all
kinds, that is, as regards the state of the particular organ)
in producing the next generation, and the continued repeti-
tion of this general mixing, panmixia, would obviously lead
to a reduction of the earlier high condition of development
of the organ. Weismann thinks, or thought, it would lead
to a steady degeneration of the organ. But few other biol-
ogists, even those ardent selectionists anxious to find in

192 DARWINISM TO-DAY.

panmixia an explanation not involving the admission of
any new organ-modifying factor, have been able to see how
panmixia can do more than simply reduce the organ to a
certain stage below the original state of greatest effective-
ness. By resorting to mathematics several writers have
determined the exact—unfortunately for their convincing
character—several degrees of reduction or degeneration that
will result from panmixia. The difficulty of explaining
degeneration (to the degree in which it is manifest in thou-
sands of known cases) on the basis of panmixia alone, is that
there is included no factor or influence that would sum up
or cumulate variations in a retrogressive direction any more
than in any other. The Darwinian variations of the use-
less organ would, by the law of error, simply keep the organ,
thus abandoned by selection, swinging about a mean but
little below the condition possessed by the organ at the time
of its abandonment. If the organ were large enough, or of
a character whereby it would entail a constant considerable
disadvantageous expense of food material to maintain it,
then selection might, on a basis of an advantageous economy
of living, tend to reduce it to a non-disadvantageous size or
character. But this disadvantage, although easily presumed
by carrying out the rigour of the struggle to a logical ex-
treme, cannot, in fact,—and biologists on the whole admit
this——in common serse be assumed.
Lamarckism offers a perfectly simple and perfectly effect-
ive and satisfactory explanation of vestigial organs and the
modus of their degeneration. But to accept this
fea pee means to accept the basic principle of Lamarck-
of vestigial ism, namely, the inheritance of acquired char-
pila acters. And it is one of Weismann’s most con-
spicuous positive achievements that he has demonstrated the
unproved character of this theory. Lamarckism says that
the first fishes to go into the dark cave suffered a partial
individual degeneration of their eyes through disuse and

OTHER THEORIES OF SPECIES-FORMING. 193

that this eye degeneration was inherited by their young,
whose eyes, already bad, suffered further degeneration in
their life-time through disuse, and that after comparatively
few generations this cumulative actual morphologic degen-
eration through disuse—and we know that unused active
organs, as muscles, stimulus-perceiving parts, etc., do actu-
ally degenerate in an individual’s life-time through disuse—
would reduce the eyes to a very degenerate condition. Other
cases of degeneration, especially of passive organs (1. @.,
where the organ’s condition was not so wholly a function
of use or disuse, but of the direct moulding influence of
extrinsic influences), are explained by Lamarckism on the
basis of the inheritance of the results of the direct action
or influence of environment on the organ. For example,
the gradual disappearance of pigment (blanching) charac-
teristic of many cave animals, would be explained by the
absence of the extrinsic factor, light, which is necessary to
stimulate pigment production.

In necessarily closing this all too brief reference* to
panmixia, it may be said that Weismann himself has in
recent years recognised its unconvincing character ; and that
Plate, a strong upholder of selection, in a most careful
weighing of panmixia, finds it capable of explaining func-
tional degeneration but not any actual considerable mor-
phological rudimentation.

The Theory of Germinal Selection was proposed by Weis-
mann in 1895, more definitively in 1896. Plate introduces

Wejsmann's [iS discussion of this theory as follows: “Its
theory ofger- aim is the rehabilitation of the selection princi-
ee ple. It shall overcome all objections and doubts
which have been raised against the selection theory and shall
act as the magician’s wand to clear all difficulties from its
way. Its strength shall avail in four directions. First, it
shall explain how not only degeneration (physiological) but
rudimentation (morphological) occurs in panmixia; second,

194 DARWINISM TO-DAY.

why exactly those variations needed for the development of
a certain adaptation appear at the right time; third, how
correlation of adaptation comes to exist; and fourth, how
variations are able to develop orthogenetically along a defi-
nite line, without depending on the necessity of a personal
selection raising them step by step.” Weismann himself
refers to the theory as ‘“‘a spring of definitively determined
variation.” In 1902, Weismann further applied the theory
to the explanation of monsters, and other cases of terato-
genesis, of “sports” (sudden or large discontinuous varia-
tions), of suddenly appearing sex-characters, of specific
talents, and still other heretofore unsatisfactorily explained
phenomena.

In defining the theory of germinal selection we come at
the very start to a difficulty based on the fact that little or

no reference has heretofore been made in this

The physical 450k to certain various theories or speculations
and chemical 4
structure of as to the ultimate structure of protoplasm, espe-
protoplasm. .

cially the protoplasm of the germ-cells. In

recognising protoplasm as the “physical basis of life’ (Hux- .
ley’s phrase), biologists have naturally tried to find in
its actual physical make-up some clue to its marvellous
capacities. The highest powers of our best microscopes,
however, reveal little more of this intimate physical struc-
ture than does our unaided eye. Probably the colloidal char-
acter of protoplasm, that is, its amorphous, non-crystalline,
viscous condition, is the most important physical fact about
it revealed by our closest examination. But this apparent
simplicity of physical structure is very unsatisfying to most
biologists, and they demand the assumption of an extremely
complex structure; a subdivision of germinal protoplasm
into structural units and groups of units, just as the chemist
assumes, in his atomic theory, a subdivision of substances
into molecules and atoms. These protoplasmic units are,
of course, invisible; like the atoms, they are beyond the see-

OTHER THEORIES OF SPECIES-FORMING. 195

ing of our microscopes. This nearly unanimous demand
on the part of biologists for a complex physical structure
of protoplasm, depends largely on the fact that our present
knowledge of the chemical constitution of protoplasm offers
absolutely no explanation of its capacities. We know that
protoplasm is composed of certain familiar elements, pres-
ent in certain proportions. But beyond that nothing; the
actual chemical relations of these component elements are
too complex for analysis. Besides, certain observations of
the processes of protoplasmic behaviour suggest strongly
the workings of a machine whose effectiveness lies in its
physical make-up. Finally, the phenomena of heredity
seem to admit of no other explanation than the assumption
of a composition of the germinal protoplasm out of myriads
of structural units actually representing the myriads of cells,
or groups of cells, of the fully developed body.

Ever since protoplasm has been recognised as the physical
basis of life, therefore, and ever since the germ-cells have
been recognised not to be miniature men and women, but,
as far as the eye and microscope go, masses of primitive
protoplasm differentiated only into cell-plasm, nucleus, and
nuclear parts (chromosomes, centrosomes, nucleoli, etc.),
there have been “atomic” theories of protoplasmic struc-
ture. Unfortunately for the standing of any one of these
theories, each working biologist seems to have made one
for himself, so that instead of one universally accepted,
hence usable and useful, atomic or unit theory such as the
chemists have—and the modern physical chemists seem
to be rebelling even against that,—biology has had a host
of protoplasmic unit theories of which the one we have here
specially to refer to is known as Weismann’s theory of
biophors and determinants. Several of the better known or
more ingenious of these theories are outlined in very sum-
mary fashion in the appendix‘ of this chapter. What we
need now to know of biophors and determinants in order to

196 DARWINISM TO-DAY.

understand the theory of germinal selection, is this: Weis-
mann conceives the protoplasm of the cell nucleus to be
composed of units called biophors—these biophors can also
migrate out into the cytoplasm surrounding the nucleus—
which are the bearers of the individual characters of the cell.
The total character of any cell, its form, make-up, and spe-
cial properties, is determined by the totality of its biophors.
These biophors are not, however, such simple structures as
the atoms of the chemist ; indeed, they are to be Icoked on as
super-molecules, as complex groups of chemical molecules,
of determined character and arrangement. Moreover, as
these biophors are life-units, they possess the essential char-
acteristics of life, that 1s, the capacity to assimilate food,
to grow, and to reproduce themselves by division. The num-
ber of different biophors is almost inconceivably enormous;
for it must equal the possibilities of variety in character
exhibited by, or capable of being exhibited by, all the cells
of the body. But as each biophor is made of many complex
molecules which may vary among themselves, and also vary
in their structural relation to each other inside the biophor,
it is not difficult, perhaps, to imagine the possible variety of
biophors to be equal to the possible variety of cell char-
acters. These biophors are conceived to be united into
fixed, indissoluble groups called determinants, each de-
terminant containing all the biophors necessary to deter-
mine the whole character of any one kind of cell. Like
the biophors the determinants can assimilate food, grow
and multiply by division. While in each specialised body-
cell there needs to be but a single determinant, namely,
one of the special kind conforming to the special kind
of cell, in the germ-cells there must be conceived to be
every kind of determinant which may be found in all
the body-cells taken together. But, fortunately, by virtue
of the determinants’ capacity for multiplication it is
not necessary to assume that there exists in the germ a

OTHER THEORIES OF SPECIES-FORMING. 197

determinant for every cell that is to develop in the body, but
only one for every different kind of cell; all cells exactly
alike can be supplied with similar determinants by the multi-
plication of the proper kind. Now Weismann’s theory of
germinal selection rests upon the assumption of a competi-
tion or “struggle” of the determinants in the germ-plasm
for food and hence for opportunity to grow, to be vigorous,
and to multiply. The germ-cells derive their food, as do
the other cells and tissues of the body, from the general
food streams circulating around and through the cells.
Weismann, recognising the absolute principle of slight varia-
tion everywhere in Nature,—it is practically impossible to
conceive of identity,—believes that the initially slightly
stronger or more capable determinants will be able to take
up larger supplies of food, even to the extent of lessening
the supply for neighbouring determinants, perhaps to the
degree of starvation. Indeed he suggests a reason for the
initial slight variations in vigour of the determinants in the
probability that the food will reach the various determinants
in slightly, purely fortuitously, variable quantity, so that
the first inequality in vigour of the determinants will depend
on the fortuitous variability of food supply, while there-
after the variability in the determinants thus produced will
enable the stronger ones to draw to themselves or take up
more food and thus accumulate determinately the initial
fortuitous inequality.

Thus when the germ-cell begins its development into
a new individual those kinds of cells, tissues, and organs
will be best developed whose determinants were most suc-
cessful in the struggle for food, while other parts of
the body may be made smaller or even may not appear
at all because of the starvation of the determinants re-
sponsible for the cells which should compose them. Also
these better-developed, larger, more vigorous determinants
of one generation will hand on to the germ-plasm of the

198 DARWINISM TO-DAY.

next generation strong and extra-vigorous daughter deter-
minants. For any determinant in the germ-plasm of a fer-
tilised egg-cell has not alone to furnish determinants which
shall control the development of body-tissues and organs
of the individual which develops from this cell, but also to
furnish daughter determinants for the new germ-plasm of
this individual. This will result in a repetition of the
extra-development in the next generation of the same organs
as were strongly developed in the first generation, and the
under-development of the same organs as were weak or
wanting in the first generation. Which process continued
is simply determinate variation, that is, variation along
fixed lines without reference to personal selec-
Dtagucts tion. Now when this variation becomes so
indeterminate marked that it is of life-and-death advantage
variation, . ‘ : 9 ge A :
or disadvantage in the life of the individual, it

will immediately become subject to the control of personal
natural selection, and under the influence of this dominant
factor in determining adaptation, either be further fostered
and fixed or be extinguished. If the increasing organ or
part due to germinal selection be one whose increase is
advantageous to the individuals possessing it, then natural
selection will preserve those individuals and the germinal
advantage of the determinants of this part will be steadily
increased, as the size and power of assimilation of the
determinants correspond to the size and vigour of the part.
By this theory Weismann believes that he has explained
away one of the most patent objections to natural selection,
viz., that it is necessary to assume, for the effective work of
selection, the timely appearance of the proper variations
necessary for the continued advantageous modification of
a part. “Knowing this factor, we remove, it seems to me,”
writes Weismann,’ “the patent contradiction of the assump-
tion that the general fitness of organisms or the adaptations
necessary to their existence, are produced by accidental

OTHER THEORIES OF SPECIES-FORMING. 199

variations—a contradiction which formed a serious stum-
bling-block to the theory of selection. Though still assum-
ing that primary variations are ‘accidental,’ I yet hope to
have demonstrated that an interior mechanism exists which
compels them to go on increasing in a definite direction, the
moment selection intervenes. Definitely directed variation
exists, but not predestined variation running on independ-
ently of the life conditions of the organism as Nageli, to
mention the position that the most extreme advocate of
this doctrine has assumed: on the contrary, the variation is
such as is elicited and controlled by those conditions them-
selves, though indirectly.”

Obviously Weismann in his theory of germinal selection
has preserved the actuality of a struggle and a selection, but
with a “rehabilitation” of natural selection in the real Dar-
Winian meaning and only fair application of the phrase the
new theory has nothing to do. It is, much more, a distinct
admission of the inadequacy of natural selection to do what
has long been claimed for it. It is the first serious attempt
at a causo-mechanical explanation of a theory of ortho-
genesis, that is, variation along determined lines.

As to our acceptance or non-acceptance of such a theory
we need say little. It consists of two purely speculative basic
assumptions: First, Weismann’s particular theory of the
ultimate structure of the germ-plasm, namely, the theory of
biophors and determinants; and secondly, the assumption ,
that there is a struggle for food among the determinants.
There is no proof of pure observation or experiment for
the theory, and there is some proof directly against it. And
yet the great need of a working hypothesis for the causo- ©
mechanical explanation of determinate variation makes us :
give such a pure speculation more attention than it might ©
otherwise get. Unfortuna the attention thus given to |
this particular theory seems tofhave resulted in the bringing ~
forward of some rather serigus objections to the possibility

ear

v2
Sra.

IGP TOTS

‘

200 DARWINISM TO-DAY.

of the truth of the theory. A few of these objections * may
be briefly stated.

According to the theory there should be plainly exhibited
in the variation of any species, decided tendencies in certain

Objections to Specific directions. In all species, in all indi-
is ea viduals, the struggle of the determinants must
tion. result in the suppression or reduction of some,
the extra-development of others. Thus variation should
not reveal itself according to the law of error, that is, should
not be distributed normally about a mean or mode. But
that is exactly the condition of variation in a majority of
those cases in which the variation of one or more organs
in any species has been statistically studied. The plotted
curve of any particular variation of this type is a symmetri-
cal curve nearly coincident with the theoretical one express-
ing the law of error for the same case.

The constancy of species is just as marked and actual a
condition as the condition of slight fluctuating variations
inside the species. This constancy is steadfast for con-
siderable time-periods. But with such an active orthogene-
sis as the theory of germinal selection provides, there could
be no such steadfast constancy. Weismann himself recog-
nised the weight of this objection to the theory, and speaks
of an attribute of “self-correction” pertaining to the germ-
plasm, which shall regulate or check too rapid an ortho-
genetic development.

The actual change of the competitive determinants due
to their obtaining an over cr under supply of food should
be one simply quantitative in degree; such germinal selec-
tion could thus lead to the change in size and strength of
organs already present in the species, but could offer no
explanation of qualitative changes, 1. e., the appearance of
new kinds of structures. Moreover, even in cases of purely
quantitative change, such familiar cases as the persistence
through long time-periods of small, rudimentary organs,

OTHER THEORIES OF SPECIES-FORMING. 20E

without any indication of further reduction, indicate a pecu-
liar cessation in the forthright working of germinal selec-
tion. Why should not the weak determinants of these weak
organs go completely to ground in the struggle?

Actual experimentation on the influence of food-supply
in development does not bear out the assumption on which
the theory of germinal selection rests. Weismann himself
gave the larve of flies, and I have given the larve of silk-
worms through their whole life-time, an abnormally small
food supply (in the case of the silkworms this supply was:
from one-fourth to one-eighth the amount normally eaten
by full-fed larve), with the only result that the mature
individuals were dwarfed; that all their parts were reduced
in size, but the actual size proportions of the various organs:
and parts, and their relations to each other, were unchanged.
The determinants seemed to share equally the hardships of
short rations rather than a few of the stronger getting the
better of the weaker. From the eggs of birds considerable
quantities of yolk have been withdrawn without modifying
appreciably the individuals developed from the eggs.

If the struggle of the determinants is really an actual and
severe one then only those of the large strong organs should
survive, all the others being starved out. Such a condition
would result in the exclusive development of monsters, 1. e..,.
individuals lacking numerous organs (the small ones), and
with the large ones all over-developed.

Rousx’s Theory of Intra-selection or the Battle of the
Parts.—Distinctly more likely to appeal to our reason is the
theory of Roux,’ proposed in 1881, to explain how one or
more organs may exhibit a progressive development or
increase in size and capacity without reference to natural
selection and also to account for the many remarkable adap-
tations of slight and delicate but extremely precise character
exhibited by various internal organs. Roux made, however,
a too radical distinction between external or superficial:

202 DARWINISM TO-DAY.

adaptations on the one hand, attributing these to the influ-
ence of natural selection, and the adaptations of internal
parts on the other, which he would attribute to the influ-
ence of his functional stimuli and of his struggle among
the inner parts of the body. This struggle, like that among
Weismann’s hypothetical determinants, is one chiefly for
food, but in Roux’s theory there is no assumption of hypo-
thetical life units, nor any lack of clearness concerning the
initiation of the actual struggle. The competing parts in
Roux’s theory are the chemical molecules composing the

Pi ona patlne cell, the cells themselves, groups or tissues of
parts in Roux's cells, and even whole organs. The spurs to the
theory are actu- ara : : ;
ally recognised COMpetition for food are functional stimuli,
structures, whose result is to set up a special demand and
necessity for more food. Roux’s classic example will make
this clear. It is a matter of fact that the fine plates and
layers of bone in the “spongy tissue” of the long bones of
the body, are so disposed as actually best to withstand the
stresses most usually brought to bear on the bones. Thus
they show a fine adaptation of arrangement, which one meets
difficulties in trying to explain as due to natural selection.
For, if we imagine the thin plates of the spongy tissue
purely miscellaneously arranged, the possible slight varia-
tions whereby a few plates at a time might fortuitously
occur in a position or direction better fit to strengthen the
whole bone, are so insignificant in proportion to the condi-
tion throughout all the rest of the bone that we cannot possi-
bly attribute to them a life-and-death value in the individual’s
struggle for existence. Roux assumes that the stresses
brought to bear on the bone during its development act as
functional stimuli to all those plates in the forming spongy
tissue, which lie in such places or at such an angle to the
stress as to be affected by them, and in response to these
stimuli, which in Roux’s belief are necessary to the normal
structural development and maintenance of any part, these

OTHER THEORIES OF SPECIES-FORMING. 203

forming bony plates will take up more food than the un-
stimulated ones, and thus will be developed at
the expense of these others. Similarly with
all those other marvellously delicate inner adap-
tations of fine and minute and oft-repeated structures to the
special functions of the organs containing these structures.
The stimulus of the function excites a trophic demand on
the part of the struggle and an actual capacity for satisfying
the demand, that soon leads to the extra-development of
the stimulated parts at the expense of adjacent similar parts
deriving food from the supply common to all. Thus Roux
would explain the exquisite adaptation of the arrange-
ment of the muscle-fibres in the walls of the blood-vessels,
the tenidia or spiral threads in the trachez of insects, the
little barbs on the feathers of birds which hold these feathers
together in almost air-tight continuity, the numerous protect-
ive hairs covering the spiracles of many insects, etc., etc.

It will be noted that the competition of the parts is really
twofold; thus, while for successful development it is neces-

Piteccagele sary for parts tO“ be successful in food-getting,
ofthe partsis this sticcess in food-getting seems to depend
ees upon the prerequisite of receiving a needed
functional stimulus. Thus there may be said to exist a com-
petition for functional stimuli. But obviously success in
this competition depends chiefly on the hazard of position.
Those plates in the forming spongy tissue of a long bone
which happen to lie where the stress comes, and in a special
direction to be affecied by it, are the winners in the compe-
tition for stimuli.

Roux’s theory has appealed strongly to many biologists,
but others have rejected it wholly, or at least as an explana-

Caen tion of fine inner adaptations. Plate takes this
cism of Roux’s latter position, but finds a great service in the
Buoy: _ theory in that “Roux has given in it a profound
analysis of the well-known fact that use strengthens and

The struggle
is for food.

204 DARWINISM TO-DAY.

disuse weakens. His is the great merit of having clearly
explained the extraordinary importance (Tragweite), in the
building of new forms and adaptive structures, of this ele-
mentary attribute of organisms. We have to thank him for
the best putting together of all those observations which
permit of but the one conclusion, that the functional stimuli
exercise a trophic activity, that is, that each organ by the
constant exercise of its function becomes stimulated to
stronger assimilation and increased multiplication of its
elementary parts, and that out of this there results a height-
ened functional capacity.” However, as Plate points out,
Thelawof this “law of functional adaptation” does not
functional adap- apply to all organs and tissues; “the teeth of
tation does not ' 5
apply to all many mammals become impaired through con-
bi et stant use, and most of the sense-organs are
apparently not bettered through use in regard to their per-
ceiving elements but only in regard to their carrying ele-
ments. Every exercise is followed by a certain fatigue
which, in cases of exhaustion, is greater than the aimed at
(ersielte) increase of functional capacity. Also the trophic
stimulation can, in certain cases, lead to hypertrophy and
other unadaptive results.” But as regards the actual “strug-
gle of the parts,’ and especially as regards the claim that
such a struggle is to account for inner adaptations, Plate, as
a consistent natural selectionist, is wholly sceptical. He
offers five objections to any usurpation of the functions of
natural selection by this intra-selection theory. First, he
holds, with Wolff, that it is impossible to place the inner
adaptations in any sharp contrast with outer adaptations.
They are contrasted only in that the former stand in a more
indirect relation to the conditions of life. Indeed a single
organ, as a claw for example, can show an external adaptive-
ness in that it might be especially well arranged to scratch
hard dry ground, and at the same time be distinctly adap-
tively constructed as regards its fine inner structure. “If

in ontogeny

OTHER THEORIES OF SPECIES-FORMING. 205

natural selection,” says Plate, “is capable of producing outer
adaptations such as making the fur of a mammal thicker
and thicker as a protection against the cold, why can it not
increase, or if advantage lies the other way, decrease, the
number of bony plates in the spongy tissue of the long
bones ?”
Second, the capacity of living substance to be stimulated
to increased food-getting is an elementary attribute of organ-
Ty ahisaen: isms just as the capacities to assimilate, to be
lation notex- irritable, and to breathe are. This special
ee capacity is not explained by the theory of intra-
selection; it is, indeed, just now wholly inexplicable. One
might perhaps fairly assume that it is the result of a gradual

development from the Protozoa onward, through the influ-

ence of individual selection. But this is no explanation of its
origin. Roux, himself, indeed, expressly declares that he
bases his theory on the proved but not explained fact of
functional adaptiveness, but some of his followers often
forget this and seem to claim that the distinctly advantage-
ous peculiarity of most tissues to be able to increase in
strength and size through use is a direct result of the
battle of the parts.

Third, Plate holds that the battle of the parts plays no
role in ontogeny. The cleavage and embryonal develop-

Battle ofthe ment are wholly controlled by heredity, so that
parts not evident there is nothing left for the battle of the parts.
There occurs a peaceful and regular split-
ting apart of the single cells and a separation of them
according to their different qualities, and it does not at all
occur that the strongest cells get all the food and the weak-
est none, but on the contrary each receives as much as it
needs for its growth. In a blastula of thirty-two cells it is
not the capacity on the part of certain cells which results in
the stronger growth of some and the weaker growth of
others, or the more rapid multiplication of some and the

206 DARWINISM TO-DAY.

less rapid of others, but, on the contrary, for each species
there is a definite law of growth which we may only explain
as the expression of a force of heredity, not capable yet of
analysis. Matters certainly do not go on in an embryo as
in an agar culture containing several kinds of bacteria of
which only that one with the greatest life force remains.
Were the development of the embryo determined by the
food-zeal of the cleavage cells, it would happen that in a
short time a few cells specially capable of assimilation would
get the upper hand, and as a consequence only a few quali-
ties be left to the embryo; a real differentiation into thou-
sands of different cell-sorts would not be possible. All the
facts of symmetry and auto-regulation in embryonic develop-
ment speak against any considerable influence of a battle of
the parts during development.
Fourth, Plate declares that in the acquirement of new
characters no selective intra-struggle takes place, or at least
in only most insignificant manner, but that the
No battle of ‘ ‘ ,
the parts inthe NeW structures arise either through the direct
aoquirement of influence of new stimuli or by natural selection
new characters, ; er as
of new germinal variations of unknown origin.
In the first place it is simply the matter of position, not at
all that of quality, that decides whether the certain cells
shall be changed or not. Think, for example, of a vessel
in whose walls the connective tissue fibres cross and recross
in all directions wholly without order, and conceive that a
constant or repeated stress in both longitudinal and trans-
verse directions is exerted on this vessel. It would result
that all those fibres lying in the absolute or approximate
directions of these stresses would be most stretched and |
would in consequence of their trophic irritability most rapidly
enlarge and increase with special rapidity. Now by the
repetition and inheritance of this result of use it would finally
come about in the course of generations that all the fibres
situated in other directions to the stresses would die out,

OTHER THEORIES OF SPECIES-FORMING. 207

and thus a definite longitudinal and transverse arrangement
of fibres in the walls of the vessel result. Without doubt,
holds Plate, much advance is won in this way, but this
specialisation of structure is not a result of intra-struggle
but rests on the elementary attribute of trophic irritability.
Not the best-qualified but the best-situated fibres have van-
quished the others by robbing them of food and thus finally
destroying them. In the second place, “many inner struc-
tures belong to the great category of passive adaptations ;
they function only through their presence and cannot thus
be further developed by use or disuse, that is, by functional
stimuli, but only by natural selection. Here belong, for
example, the stratification of the lens in the human eye, the
apodemes (inner projections of the chitinised cuticula)
which protect the ventral nerve-cord of the crabs, the chitin
hooks which hold together the fore and hind wings of many
insects, and the similar structures which bind together the
secondary branches of the feather vanes of birds. These
inner adaptations cannot have resulted through the influence
of light or of nervous function or flight. There is but one
explanation possible; namely, that natural selection has
seized on and developed fortuitously appearing germinal
variations. But if natural selection can produce such inner
adaptations why can it not then produce all the others?”

Fifth, Plate points out that Roux’s theory is based on the
inheritance of those special body characters which are

“ee acquired through the battle of the parts—more
Rour’s theory tightly, Plate holds, through functional adapta-
er tion,—so that to accept the theory, one has to
acquired char- declare, to that degree, a belief in the inherit-
pevert: ance of acquired characters. Thus from the
start, the neo-Darwinians cannot accept the theory.

After all what is this theory of Roux’s but a refinement, a
special case, of the broader and more general long-known
Lamarckian theory of the modifying and formative influ-

208 DARWINISM TO-DAY.

ence of use and disuse, accumulated through inheritance?
That is, if we accept Plate’s analysis that the theory is
really not one of a battle of the parts, but of
The battle of : : :
the parts theory the effects of functional stimuli. And however
ri oer the proposer of the theory may protest against
such an apparent violent setting over of it from
the category of selection (Darwinian) theories into that of
the inheritance of use (Lamarckian) theories, I believe that
most of us will see the justness of Plate’s analysis. I do
not believe that Roux’s theory in any way strengthens the
selection conception. To my mind, indeed, it is simply a
concession of the inadequacy of selection to initiate adapta-
tion, and a welcome and satisfying explanation of how such
an initiation may occur in many cases, in certain cases, that
is, Of active adaptations. Plate’s argument that natural
selection must be the only explanation for the cases of
passive adaptations and hence may be held capable for
accounting for the active ones, has no conviction for me, for
I do not believe that natural selection is the only possible
explanation of the passive cases. In fact, I cannot conceive
it to be a possible explanation of the initiation of these cases.
And I am glad to find in Roux’s theory—even if it be not
exactly applied in Roux’s own sense—a mechanical expla-
nation of the possibility of initiating certain fine and delicate
inner adaptations.
Organic Selection.—An interesting attempt to escape from
the difnctlties“which are imposed on one by an absolute
adherence to Weismann’s doctrine of the impos-
Organic selec- _., .,. ; ; :
tion, orthoplasy, Sibility of the inheritance of acquired characters
or ontogenetic § coupled with a belief in the inadequacy of the
selection. ; ; . ae
slight fluctuating germinal variations to afford
handles for the action of natural selection, is the theory va-
riously called organic selection, or orthoplasy, proposed by
Baldwin * and Osborn® in America, and Lloyd Morgan” in
England. This theory, which might also be called one of

OTHER THEORIES OF SPECIES-FORMING. 209

“ontogenetic selection,” or of “coincident selection,” is that
the personal selection, or individual survival, among’ indi-
viduals of a species does not necessarily depend solely upon
congenital variation but may, must, indeed, depend on any
ontogenetically acquired adaptations as well. As in many
cases these ontogenetic adaptations are considerable, they
will often carry individuals through very critical periods in
their lives. But the individuals showing these ontogenetic
adaptations in best degree will be those which actually pos-
sess certain slight congenital variations, especially of the

nervous system or coérdinating nerve centres, “which lend’

themselves to intelligent initiative, adaptive, or mechanical
modification during the lifetime of the creatures which have
them.” The ontogenetic adaptations may occur regularly
in the lives of successive generations of individuals if the
environment remains fairly constant. During these suc-
cessive generations the congenital variations of brain, say,
which make the successful ontogenetic adaptations possible,
will by selection of the best ontogenetically varying individ-
uals be themselves selected, and the species thus gradually be
modified in a determinate direction. Also congenital varia-
tions of nearly the same nature as the ontogenetic variations,
or of a nature to supply the same need, will have time (that
is, more chance, because of the longer time and repeated
generations) to appear. In this case these advantageous
variations can be transmitted directly by heredity, and thus
a permanent adaptation be effected which will seem to be the
result of the inheritance of an acquired character (2. e., the
similar ontogenetic modifications) but which in reality is
only the normal inheritance of a congenital variation.

In the language of all the sponsors for this theory there
seems to be a suggestion of the piling up or adding together
of congenital variations, not simply those of brain or other
control centre which make the ontogenetic modifications
possible, but also of these modifications themselves during the

crt ate

210 = DARWINISM TO-DAY.

successive generations through which the species is safely
carried by the temporary regularly appearing ontogenetic
adaptations. But there is nothing in strict neo-Darwinism
to permit of any such idea of increase. Such moving for-
ward without the aid of selection can. only beeen td
the adoption of some theory of orthogenesis. Either the con-
genital variations are of such a character that the resulting
ontogenetic modifications are not fairly to be distinguished
from them, in which case they are assumed to be large
enough from the start to afford handles for natural selection
(which the proposers of the theory are not claiming), or
they depend for their preservation on a kind of happy coinci-
dence in occurrence with similar more effective ontogenetic
modifications which are really large enough to save the life
of the organism and hence the slight congenital variations
along the same line. But in this latter case organic selection
cannot demand much discussion until it explains away a

Delageand radical failing pointed out clearly by Delage
eae and Plate. This is simply that, in the face of
tion, the large character which ontogenetic adapta-
tion may and often does possess, those individuals in which
the slight congenital variations in the right direction finally
appear will have no special advantage over those in which
they do not appear; the large and effective character of the
ontogenetic adaptations, which are common to both kinds of
individuals, being quite sufficient to determine the result of
personal selection. The congenital variations will be too
small in comparison with the ontogenetic variations to cut
any figure in the fate of the individuals, and there is no
reason at all to believe that individuals showing the slight
congenital variations in the right direction will be the only
ones to show the saving large ontogenetic adaptations.
Plate suggests the following case to show the inutility of
this theory : Suppose an antelope species to have a leg muscle
averaging seven cm, in thickness, and several individuals to

OTHER THEORIES OF SPECIES-FORMING. 211

show a congenital variation bringing the leg muscle up to
eight cm. of thickness. Now if it requires a leg muscle of
eight cm. for safety, as a matter of fact almost all the indi-
viduals of the species will quickly bring their leg muscles up
to that size by use. But suppose the actual need for safety
was a leg muscle of fourteen cm., then only those individuals
specially capable of that ontogenetic adaptation, 1. e. (modi-
fication of the leg muscle by use and trophic irritability), up
to fourteen cm., would be saved; and undoubtedly among
these the original eight cm. individuals ought to stand in_
slightly higher numerical proportion (in regard to their
original numerical standing in the species) than the origi-
nally seven cm. individuals. Since, however, these eight cm.
individuals originally existed only in comparatively small
number, and since they possess no special means of recognis-
ing each other and distinguishing each other from the
original seven cm. individuals, mixed mating will inevitably
soon swamp the original congenital increase of one cm. in
muscle thickness.

In connection with the explanation of this theory it will
certainly occur to some of my readers, as it has to me, to ask

Banviek of if it is not a dangerous proposal to give to
assuming too = ontogenetic adaptations a greater worth in
great import- ee eae Oe :
aucee iets. ceciding the fate of individuals durime the
genetic selection. strygole for existence than the congenital varia-
tions. Is this not proposing to take away from the fluctuat-
ing, individiual, so-called Darwinian variations practically
all worth and capacity except as they are of immediate use
to the just-born individuals, 7. e., before the ontogenetic
adaptations have been able to develop? Indeed, why is it not
a perfectly legitimate and a serious criticism of congenital
fluctuating variations that they must be overshadowed, hid-
den, and overwhelmed by the quick and large ontogenetic
or individual modification of which practically all organisms
are capable? Why will not those individuals born with the

212 DARWINISM TO-DAY.

better and larger capacity to adapt themselves during their
ontogeny to their needs win in the struggle for existence
rather than those born with predetermined slightly larger
leg, slightly stronger muscle, etc.? What is needed is
capacity to develop by use and functional stimulus a much
stronger muscle, a much swifter flight than the average.
Those individuals that are capable of such considerable and
really worth while ontogenetic adaptation will win in the
struggle for existence; and while they may not hand down
by inheritance their actwatty acquired characters, will they
not hand down their inherited congenital capacity for con-
siderable and effective ontogenetic adaptation?

APPENDIX.

*For a fairly complete bibliography, with abstracts, of all the
important discussions of species-forming theories published since
1895, see L’Année Biologique (ed. Y. Delage). For bibliography
and abstracts, also see Zoologischer Jahresbericht, issued annually
by the Naples Zoological Station. See also discussions and notes
in various biological journals, as Biologisches Centralblatt, Natural
Science (now discontinued), Nature, Science, American Naturalist,
etc.

* For a careful account and discussion of Weismann’s work and
theories as far as developed up to 1893, see Romanes, “An Exami-

List of Weise mation of Weismannism,” 1803. Weismann’s pres-
mann’s evolution ent-day position and his arguments for the selection
Papes®: theories are set out in his ‘“Vortrage tiber die De-
scendenztheorie,” 2 vols., 1902, which we may look on as consti-
tuting a manual of neo-Darwinism, treating all the more familiar
bionomic phenomena and conditions as explained by selection.
The following is a chronological list of the more important of
Weismann’s publications:

“Uber die Berechtigung der Darwin’schen Theorie,” 1868.

“Uber den Einfluss der Isolirung auf die Artbildung,” 1872.

“Studien zur Descendenztheorie: I, Uber den Saison-Dimorphis-
mus der Schmetterlinge,” 1875.

“Uber die Dauer des Lebens,” 1882.

“Uber die Vererbung,” 1883.

OTHER THEORIES OF SPECIES-FORMING. 213

“Uber Leben und Tod,” 1884.
“Die Continuitat des Keimplasmas als Grundlage einer Theorie
der Vererbung,” 1885.

“Uber den Riickschritt in der Natur,” 1886.

“Uber die Bedeutung der Sexuellen Fortpflanzung fiir die Selec-
tionstheorie,”’ 1887.

“Uber die Zahl der Richtungskérper und iiber ihre Bedeutung
fiir die Vererbung,” 1887.

“Botanische Beweise fur eine Vererbung erworbener Eigenschaf-

ben, 1888,

“Uber die Hypothese einer Vererbung von Verletzungen,” 1880.

“Bemerkungen zu einigen Tages Probleme,” 1890.

“Gedanken tber Musik bei Tieren und beim Menschen.” 1890.

“Aufsatze uber Vererbung und verwandte Biologie,” 1892. (This
includes the eleven preceding papers now published in book-
form. These essays have also been translated into French,
by H. de Varigny, and published under the title: ‘““Essais sur
lHérédité et la Sélection Naturelle,” 1892; and also in Eng-
lish as ‘““Essays upon Heredity and Kindred Biological Prob-
lems,” trans. and ed. by Poulton, Shoneland, and Shipley, 2
vols., 1891 and 1893.

“Amphimixis oder die Vermischung der Individuen,” 1891.

“Das Keimplasma; eine Theorie der Vererbung,” 1892; Eng.
trans. by Parker and Ronnfeldt, as “The Germ-plasm; a
Theory of Heredity,” 1893.

“Die Allmacht der Naturztichtung, eine Erwiderung an H. Spen-
cer,” 1893; also in English as “‘The All-sufficiency of Natural
Selection,” in the Contemp. Review, Vol. LXIV, pp. 309-338,
596-610, 1893.

“The Effects of External Influences upon Development,” Romanes
Lectures, 1894; also in German as “Aussere Einfliisse als
Entwicklungsreize,” 1894.

“Neue Gedanken zur Vererbungsfrage,” 1804.

“Uber Germinal-Selection,” in Compt. Rendus, 3d Congress In-
ternat. Zool., 1896; also, in English, trans. and ed. by Mc-
Cormack, as “On Germinal Selection as a Source of Definite
Variation,” 1806.

“Thatsachen u. Auslegungen in Bezug auf Regeneration, ” Anat.
Anzeig., Vol. XV, 1890.

“Vortrage tiber Descendenztheorie,”’ 2 vols., 1902; also in Eng.,,
trans. by J. A. Thomson as “Lectures on the Theory of
Descent.” 2 vols., 1904.

* For a detailed critical discussion of panmixia, see Wolff, “Der

gegenwartige Stand des Darwinismus,” 1806.

214 DARWINISM TO-DAY.

* Various theories of ultimate protoplasmic structure have been
proposed to explain what is not really known about this substance.

Theories of ul- hese theories refer almost exclusively to the physi-
timate protoplas- cal, rather than the chemical, make-up of protoplasm,
micstructuree and for the most part have been proposed with
special attention to the germ-plasm, 7. e., the protoplasm of the sperm-
and egg-cells. The spur to the formation of these theories is the
necessity that biologists have felt imposed on them from the be-
ginning of the study of heredity and development of offering some
rational explanation of those phenomena. That from a single germ-
cell formed by the fusion of a sperm-cell and an egg-cell from
different parents, a complete new organism composed of millions
of cells of manifold variety of specialisation and arrangement can
develop, is wonder enough; but that this new organism shall repeat
in all its parts with extraordinary fidelity the structure and physi-
cal idiosyncrasies of one, or show a combination of the character-
istics of both, of the individuals from which came the original
single sperm- and single egg-cell, adds wonder to wonder. What
physical or structural basis is there in the fertilised egg-cell that it
can represent in its tiny self the whole of a giant body, like that of
an elephant, whose every detail it can, by a process of development
under suitable extrinsic conditions of temperature, food-supply, etc.,
repeat in a new creature. The answers to this, all purely specula-
tive, or more fairly theoretical, because some of the answers at
least have been guarded in their forming by all the care which a
rigorous scientific attitude toward hypothesis demands, are many
and various, and date from the days of the Greek philosophers to
the present hour. It would take too much space and carry us too
far afield to attempt anything like an explanatory list of even all
of the better known of these general theories of the invisible ulti-
mate structure of the germ-plasm here, but by selecting seven or
eight types of the principal categories or kinds of these theories,
and briefly explaining them, we.may have at least some conception
of the attitude that biologists take toward this great problem. The
reader who has a fancy for following this subject further is re-
ferred to the admirably full and lucid treatment of it in Delage’s
great work, “L’Hérédité” (2d ed., pp. 431-772, 1903).

Most of these theories include much more in them than a santa
speculation as to the ultimate structure of the life-substance; they
attempt to explain all the phenomena of life, motion, nutrition,
growth, reproduction, development, heredity, variation, etc., with
reference to some assumed ultimate make-up of the primitive life-
substance, and the relation of this structure to the known physico-
chemical forces and conditions of Nature. Most of the older

OTHER THEORIES OF SPECIES-FORMING. 215

theories assumed a peculiar vital force, which is not assumed in
the later ones, although exception must be made.to this statement in
favour of the point of view held by the recent so-called neo-Vitalists,
those present-day workers who admit the hopelessness of trying to
reduce all vital phenomena to a physico-chemical basis.

An old type of theory of heredity and structure of the germ-.
plasm, widely held in the seventeenth and eighteenth centuries, is

Encasement that of the “encasement of the germ” in one of the
theory. germ-cells, either the spermatozoid or the egg. The
essential part of this theory is that the new organism is assumed
actually to exist in miniature, with all its parts present, in one of the
germ-cells, and in this miniature body must exist, by repeated encase-
ment, all its future progeny. Whether the believer in this theory con-
sidered the tiny new creature, only needing to swell and grow to be
complete, to be encased in the sperm-cell or the egg-cell, ranked
him respectively with the spermatists or the ovalists. A vigorous
strife raged between these two factions among the upholders of
this simple and effective explanation of heredity which led to cer-
tain interesting compromises. A commonly held one was that the
sperm-cell furnished the spiritual element, the egg-cell the material
and mechanical elements of the new creature. Another, held by
Linnzus, the great botanist and father of biological classification,
was that, in plants, the egg (ovule) furnished the internal and re-
productive organs, while the sperm-cell (pollen) furnished the exter-
nal and vegetative parts. De Candolle, another great botanist, held
just the reverse of this view. All these theories of an actual
encasement in the germ-cells of a whole or part of a new organism
were not mere guesses, but were based on what men thought they
saw through their microscopes. The long reign of these theories,
now shown to be utterly absurd, illustrates well the constant dan-
ger which attends our attempts in all biological study to interpret
what we see when working at the limits of visibility. With our
much-improved microscopes we laugh at the fantasies which the
microscopic vision of our eighteenth-century co-workers raised up.
Who may say that our own interpretations of plasm-structure may
not seem as absurd to the biologists of the next century?

By far the great majority of theories of ultimate protoplasmic
structure belong to what Delage calls the category of theories of

Micromeric micromerism. Which means simply that all these
theories. theories assume a composition of the plasm out of
minute ultra-microscopic units of structure, which are also units
of life, for all these units are presumed to be endowed with the
essential life-attributes. These units may be looked on, as they
were by Buffon, as universal, indestructible, hence immortal, parti-

216 DARWINISM TO-DAY.

cles, or, as they are in most of the micromeric theories, as living
particles which are destroyed with the death of the organism
which they compose. In this latter type of assumption the units
are, according to some theories, all of the same nature, all exer-
cising an equal influence in determining the character of a devel-
oping organism (Spencer, Haacke, His, Cope); or they are, as
assumed in other theories, of various character and charged with
various functions. This latter kind of unit is held by some authors.
to be actually representative either of ancestral plasmas (Weismann)
or of the actual body-cells of the parent (Darwin, Galton, Brooks,
Hallez), or of elementary characteristics and functions of the
organism (Nageli, Kolliker, de Vries, O. Hertwig), or at the same
time of both body-parts and elementary characteristics (Weismann’s.
latest theory).

Buffon’s theory assumed that ‘the substance of which organisms
are composed differs essentially from that which composes the

Buffon’s inorganic bodies. Organisms are composed of special
theory. particles, the organic molecules. These molecules are
universal and indestructible: universal in that they exist everywhere
where life has access, indestructible in that death and the dissolution
which follows destroy the organisms, break down the molecular com-
binations which constitute them, but do not reach the molecules
themselves. These are only separated, put at liberty, but remain
ready to enter into new groupings. While they cannot be de-
stroyed, neither do they increase in numbers. They form nothing
actually new, either spontaneously, or by means of old ones, so
that, measured by these organic molecules, the total quantity of life
in the universe is invariable’ (Delage). Nearly a hundred years.
later Bechamp (1883) proposed a theory similar to Buffon’s in
which he assumed the composition of organisms out of minute
elementary living particles called microzymes. Like Buffon’s
organic molecules they are indestructible, and they are strewed in
innumerable numbers through earth, air, and water. They owe their
origin to special creation by God.

Of the non-immortal kind of micromeres Spencer’s physiological
units represent a general type favoured by numerous theorists:
namely, living units all of the same nature and active because of
their polarity, their form and molecular forces, or their vibratory
motion. Spencer’s physiological units are active because of their
polarity, but the annular atoms of Dolbear’s theory and the
plastidules of the slightly varying theories of Haeckel, His, Cope,
and others, owe their active properties to their vibratory motion.

According to Spencer (1864). there exist between the cells
(morphological life-units) and the molecules which compose them

OTHER THEORIES OF SPECIES-FORMING. 217

(chemical units), units of a third order (physiological units) com-
Spencer's posed of groups of molecules. These units are very
theory. small but very complex, and are the smallest masses in
which living substance can occur. Most of the micromeric theories,
which come after Spencer’s, adopt this conception of a life-unit, very
small, but composed of an aggregate of molecules, and therefore
very complex. To his physiological units Spencer attributed a
polarity, wholly analogous with that possessed by the molecules
of crystalline substances. It is owing to this delicate, precise
polarity, varying of course with the varying molecular consti-
tution of the units, that they possess the capacity of actively
arranging themselves in the varied groupings normal to the parts
of the organisms. “Thus the resemblance is perfect between the
chemical polarity which causes crystallisation and that of the
physiological units which produces the form of organisms. In one
case the chemical molecules group themselves in a manner to form
an aggregate of definite but simple form, cubical, prismatic,
rhomboidal, with their parts arranged en tremies, aiguilles, croix
de Saint André, boules épineuses, etc. In the other the units group
themselves in a body of a form less rigorously defined but which
may be very complicated: such as a plant or an animal.” ( Delage.)
Of the theories in which the living units are assumed to be of
different kinds, and endowed with different functions, some assume
the units to be not directly representative of different cells or parts
of the body, while others assume this truly representative condition.
Of the first sort are a number of theories like those of Berthold,
Geddes, and others, in which the units are taken to be actual
chemical molecules, endowed with activity through special physico-
chemical properties or through purely chemical ones, while still
others keep to the more usual type of a unit of a higher order
than a molecule, in which case also this unit is looked on as spe-
cially active because of particular electrical (Fol) or chemical
(Altmann and Maggi) or vital (Wiesner) endowment. But all of
these theories are much like each other and are much like Spencer’s
theory in regard at least to the assumed units. Different, how-
ever, is the type of theory which introduces the assumption that
the fundamental life-units are directly representative of either
the specific cells, parts, or elementary characteristics of the organ-
ism. This is the kind of unit especially favoured by the men
who had, in their formation of a theory, a special eye to the
problem of heredity. How is the single germ-cell to be the bearer
of the “heredity” of the organism from which it comes? what
more simple to assume than that this cell shall be composed of
minute particles gathered from all the cells or groups of similar

aes 2 oo: DARWINISM TO-DAY.

cells of the body of the parent? And that is precisely the charac-
teristic assumption, dressed up in an ingenious variety of form,
which charac-erises the theories of life-units most favoured at
present: such theories are those of Darwin, Galton, Brooks, Nageli,
de Vries, Hertwig, and Weismann. In some of these, interesting
attempts are introduced to connect the assumed structure with
the actually observed finer structure of the nuclear protoplasm, by
introducing combinations of the fundamental units, in one or two,
or even three, successive degrees until an aggregation is reached

which corresponds with those microscopic structures, the chromo-.

somes, or chromatin granules or threads, which are actually visible
to the microscope-aided eye. The most recent one of the theories
of this general type is that of Weismann’s biophors and determi-
nants structure of the germ-plasm, already explained in connection
with the presentation of his theory of germinal selection (see pp.
193 ff.). As other examples we may note especially Darwin’s,
called the theory of the pangenesis of gemmules; and Nageli’s,
‘called the theory of micelle and idioplasm.

Darwin’s gemmules are extremely minute particles, which are
formed in all the various cells of the body and are capable of repro-

Darwin's ducing themselves rapidly and in great numbers by
theory. repeated division, and which, by virtue of their minute
size and an innate activity due to a sort of affinity or attraction exist-
ing between them and other substances, move about freely in the body,
penetrating any membranes, and arranging themselves with a deli-
cate precision just where they are most needed. When a gemmule
enters an undifferentiated or developing cell as yet containing no
other gemmules, it controls the development of that cell so that it
becomes a cell of the type from which the gemmule had birth, each
gemmule representing thus exactly the characteristics and the type
of its mother cell. Thanks to the delicate and precise adjustment
of affinities, migrating gemmules only enter those cells which they
really should enter in order that a normal development of all the
cells of the body should go on. But those few cells of the body
which are destined to become germ-cells, that is the spermatozoids
and eggs in animals, the pollen grains and ovules in plants, receive
during their formation gemmules from all the other cells of the
body. Not only from all the cells of the fully developed body, but
from all those ephemeral cells which arise and live for a while
during the ontogeny of the parent, performing certain special func-
tions and then making way for the definitive cells of the mature
organism. Thus in the germ-cells are stored actual physical repre-
sentatives of all the cells which have existed during the whole life
of the parent body. These innumerable gemmules remain inactive

-—5
——

OTHER THEORIES OF SPECIES-FORMING. 219

jn the germ-cells until, after fertilisation, the egg-cell begins its
development. Then as the cells of the new organism begin to be
produced, the gemmules become active and each one moves into
the cell it should control and there directs its further development
into precisely the kind of cell it should be at precisely the time it
should be this kind of cell, until there results from this gemmule-
controlled development a photographic reproduction of the parent
body.

Nageli’s conception is that when the complex life-characterising al-
buminous substances took their birth in an aqueous liquid, they would

Nageli’s be precipitated, as they are not soluble in water. This
theory, precipitate is formed of small masses, a sort of organic
crystals, which may be called micelle. And just as an inorganic
crystal deposited in a saturated saline solution of the same nature
‘determines the deposit on its surface of the dissolved molecules in
the form of little crystals, and by this means grows, so wherever
any micellz are formed they facilitate within their sphere of influ-
ence the precipitation of others, so that this production of micelle
instead of taking place miscellaneously through the liquid will be
localised at certain points. Thus arise aggregates of albuminous
substance, in the condition of micelle, forming the primitive
protoplasm. The micelle, although insoluble in water, have a great
affinity for it, and each one at the time of its precipitation fixes
around itself a thin layer of water, at least as thick as a water
molecule. Thus, all the micelle grouped together in a bit of primi-
tive protoplasm are separated from each other, and also held to-
gether by a layer of water as thick as two water molecules. This
water forms an integral part of the protoplasm. By virtue of it, an
aggregate of albuminous micelle can increase by intercalcation as
well as by the addition of new micelle on the outer surface. By
admitting more or less water the protoplasmic mass may become
more or less nearly fluid. Thus are accounted for the various
densities always met with in the different parts of a protoplasmic
cell. . .

A further essential part of Nageli’s theory is an arrangement of
the primitive protoplasm in two ways, resulting in two kinds of it,
which are called nutritive plasm and idioplasm respectively. This
arrangement depends on the molecular forces pertaining to the
micelle, and the difference, resulting in two kinds of plasm, depends
upon the relative situation of the micelle composing the mass, just
how this affects them differently, however, not being made very clear.
But the differentiation is very important, for it is the idioplasm
alone which contains the essential life-properties and which really
Zives rise to life with all its variety and complexity. This idioplasm

220 DARWINISM TO-DAY.

is formed at first in scattered bits in the nutritive plasm mass, but
as these bits increase they join and become united into a network
surrounded by and containing in its meshes the nutritive plasm.
And one of the most interesting parts of Nageli’s hypothesis is that
he conceives this network of idioplasm not to be limited by cell
boundaries but to penetrate from one cell into adjacent cells and
thus to spread through and unite in a most significant and important
way all the cells and tissues of the body. It is just this sort
of a ramifying, stimulus-carrying, protoplasmic network connect-
ing all the parts of the body that the believers in the inheritance
of acquired characters seem to need as a mechanism to transmit
from soma to germ-cells the effects of external and functional
stimuli.

Next, the theory of intra-cellular pangenesis of de Vries may
be briefly stated. This theory has become the more important be-
cause of the great interest aroused by and the large appreciation
given to the mutations theory of species-forming of the same
biologist. De Vries’s theory of intra-cellular pangenesis has much
in common with Darwin’s theory of the pangenesis of gemmules,
but it is able to do away with that particularly weak part of Dar-
win’s theory, which postulated the circulation of the gemmules.
throughout the organism in order that they should meet in the
germ-cells and modify these cells in a parallel way with the modi-
fications occurring in the peripheral organs. Darwin had to postu-
late this circulation of the gemmules through the organism in order
to explain the phenomena of regeneration, and the heredity of
acquired characters. Now that the heredity of acquired characters
has been shown to be at best an extremely doubtful phenomenon,
and that regeneration is explicable by other means, de Vries has.
been able to drop this weakest part of the Darwinian conception.
So that in the theory of the later biologist, the circulation of gem-
mules does not extend from one cell to another throughout the
body of the organism, but limits itself to that particular cell in
which it is created and circulates only between the nucleus and
cytoplasm, from which comes the name, “intra-cellular pangenesis,”’
as distinguished from Darwinian pangenesis. De Vries’ theory may
be abstracted as follows (following Delage) :

The form and properties of cells result from their protoplasmic
composition just as the properties of the inorganic bodies result

De Vries’s from their chemical composition. Is it necessary, then,
theory, to admit that there are as many kinds of protoplasm as
there are different sorts of cells in the organised beings? When one
recalls how many different cells there are in a single organism, and
that the homologous cells are not identical in different species, one.

1 a
aie
Te

OTHER THEORIES OF SPECIES-FORMING. 221

realises the incalculable number of these cells and despite the rich-
ness in variety of proteid substances, it will be impossible to con-
ceive that each kind of cell should have its own kind of proto-
plasm. There is here, apparently, an insurmountable difficulty, but
one which it is easy to do away with by a very simple concep-
tion. This conception consists in distributing the complex charac-
ters and properties, innumerable in living beings, into elementary
characters and properties much less numerous, which, by varying
combinations, produce the almost infinite variety that we observe
in the inorganic world. Just as with a score and a half of letters
one may form all of the words of the human language, so with the
elementary properties of which the actual number is still very con-
siderable, one may reproduce all the characters of living beings in
all their variety and complexity. It suffices, then, to admit that
these elementary characters and properties are represented by as
many material particles, and the problem is solved. These particles
are the pangenes.

The pangenes, then, are small, organic particles, invisible to
the microscope, formed of an enormous number of chemical mole-
cules and differing from the most complex chemical substances
by three properties which are common to all of them and which
are characteristic of living matter; they nourish themselves, in-
crease in size, and multiply themselves by division. Beside these
three general properties which make living molecules of them,
the pangenes possess particular properties depending upon their
chemical constitution, differing for each of them, and which are
bound to them indissolubly in such a manner that, wherever a
pangene finds itself, the elementary property or character special to
it will show itself if internal and external conditions permit of this
manifestation. Latent or patent, potentially or evidently, the char-
acter is always there where is the corresponding pangene. Each
cell contains a great number of pangenes in activity, and its charac-
ters and properties in sum are the resultant of the elementary
characters and properties of the pangenes composing it: just as the
anatomical and physiological characters and properties of the living
individual are resultant of the anatomical and physiological charac-
ters of the cells composing it.

It is necessary to conceive of the cellular protoplasm as formed
of innumerable pangenes bathed in a liquid in which are dissolved
substances purely chemical: albumen, glucose, salts, etc. Perhaps
similar substances penetrate the pangenes themselves, but we do
not know this.

The nucleus contains in general all the kinds of pangenes that
compose the individual. But these pangenes are there in a sort

g2e DARWINISM TO-DAY.

of inactivity, in reserve, in order to be transmitted to the daughter
nucleus when the cell divides. They can divide themselves, and it
is indeed necessary that this be so in order that the two daughter
nuclei can each receive a complete lot of the representative pan-
genes; but they do not manifest in the nucleus their special proper-
ties, which remain in a latent state. There is no exception to this
except in the case of those certain pangenes which control the
division of the nucleus. These enter into activity at the necessary
moment in order to determine the characters of the division and
in particular the position of the plane of segmentation.

The cytoplasm is also composed of pangenes; but these pangenes,
with the exception of those which come from the cytoplasm of the
egg, come from the nucleus. From the nucleus there come, in fact,
pangenes which distribute themselves in the cytoplasm and multiply
there abundantly. These pangenes are exclusively those of which
the cytoplasm has need in order to manifest characters and proper-
ties which belong to the cell, and it is by delivering to it such and
such pangenes and no others that the nucleus rules the cytoplasm,
which would remain inert were it not for this infusion of living
and active particles.

There is, then, a great difference between the nucleus and the
cytoplasm from the point of view of the pangenetic constitution.
Each nucleus contains in general all the pangenes of the individual
united undoubtedly into groups more or less considerable, which lie
in the chromatic filaments, and these groups, analogous to the
gemmules of Darwin’s theory, probably form those little grains
arranged in rows, which are revealed under a great microscopic
magnification of the chromatic threads. But there are one, two, or,
at most, a small number of pangenes of each kind; all are inactive
save at the moment of division, those which rule this phenomenon;
they can multiply themselves but slightly, and in general they do
not divide except to replace those which emigrate into the cyto-
plasm and to furnish at the moment of division to each daughter
nucleus the complete lot which it ought to receive. In the cyto-
plasm, on the contrary, there is but a small number of kinds of
pangenes immigrated from the nucleus in the quantity exactly
necessary, but there these pangenes are enormously multiplying, so
that there is a very great number of each kind, and they are almost
always in a state of activity.

B. Hatschek has recently proposed (‘““Hypothese der Organischen
Vererbung,” 1905) a new micromeric theory which postulates that

Hatschek’s the protoplasm is composed of two different kinds cf
theory. biomolecules; one called ergatules, which function as-
similatively, that is, take up food-stuff and excrete waste, but do not

OTHER THEORIES OF SPECIES-FORMING. 223:

possess a capacity for growth or self-reproduction; second, the gen-
eratules, which have no particular functional work to perform but can
grow and reproduce themselves and can carry over this capacity of.
reproduction to the ergatules, because they can fuse with them or
attach themselves to them and thus carry over to them their char--
acteristic peculiarities. These generatules are looked on as the
chemical radical of the ergatules, and become therefore the directly
determining agents for all peculiarities of the body. The ergatules:
sit chiefly in the cytoplasm of the cell, while the generatules lie in the
cell nucleus, especially in the chromosomes, and therefore render
these the bearers of hereditary characteristics.

Thus baldly and wholly incompletely stated these theories of
ultimate plasm structure which shall be of a sort to agree with all
the varied phenomena of life, and particularly those of heredity,
show, unfortunately, only their fantastic face. For as it is pre-
cisely in showing how the postulated structure and properties are:
perfectly consonant with all the known phenomena of life that
these theories have their actual interest and strength, a fantastic:
and improbable face shown as to this robs them of all interest. But,.
perhaps, it is well that the fantastic aspect of them should be first
recognised. For it is only fair to say that the ingenuity and plausi-.
bility, the precise and exhaustive development of detail, of some of
these theories, are really dangerous to the layman who first happens:
to read a full and well-stated account of one of them by an enthu-
siastic upholder. One’s eyes become closed to, the. fact..that.all.the
structure and performancé that seem SO natural, and fit in so
exactly with all” that’ “we” acttially “know” of the’ ‘phenomena “of. ‘life,
havénot béen seen, only imagined. ‘One needs an introduction to
these theories which insists above all on their wholly hypothetical!
character. Otherwise one is surprisingly readily hypnotised into
accepting one or the other of them as a statement of fact. These
general theories are the atomic theories of biology without one--
tenth the probability of truth or one-tenth the actual acceptance
in science that the atomic theory of the chemists has. And even:
that 1s beginning to be discarded in modern chemistry. These:
theories are, as Weismann has said, the outcome of the fact that
“the deeper one studies into the phenomena of heredity, the more:
one is convinced that something of this kind of a condition [of a
composition of the fundamental life substance out of ultra-micro-
scopic units bearing a certain spatial relation, and one of attractions
-and repulsions to each other] must really’ exist: for it is impossible
.to explain the observed phenomena in any other way, that is, by
-any much simpler assumption.” But on the other hand a sufficient
reason against accepting any one of these highly developed theories:

224 DARWINISM TO-DAY.

of the structure and functional capacity of invisible life-units, is
the sagacious one of Delage when he says that simply by the law

Delage’s of probabilities it will be impossible by pure imagining
criticisms. to explain correctly in detail the ultimate structure
of protoplasm. Has any one, asks Delage, guessed in advance, with
the least truth, structures which the microscope has later been able
to reveal to us? Has any one guessed the cross-striation of muscles,
the cilia of vibratile epithelium, the prolongations of the nerve-
cells, the make-up of the retina, or the organ of Corti, the chromo-
somes, the centrosome? Distinctly not. Delage points out that
the chemists had a much better chance to hit the truth in supposing
atomic structure, for they had a much less complex condition to
perceive, and they had approached in their positive knowledge very
much nearer the hypothetical element which they adopted.

Le Dantec criticises the micromeric theories of protoplasmic
structure by saying that all these theories seek to make mysteries

Le Dantec’s Clearer, complex things simpler, by reducing large
criticisms, things to small ones. A man, for example (he says)
is composed of 60 trillions of cells and is nevertheless produced by
sexual elements of very small size; here is a phenomenon to ex-
plain. The micromerist says that the difficulty of this explanation
would be less (or at least not so sharply defined!) if one divided
the problem into 60 trillions of parts; that is, 1f one replaced the
reproduction of man by 60 trillions of partial reproduction. One
has therefore imagined particles infinitely small which are to the
cells what the sexual cells are to the man. And this comparison has
been, consciously or not, claims Le Dantec, the point of departure
of all the systems of particulate representation in the germ-
plasm.

We have simply substituted for a single heredity, continues the
critic, 60 trillions of partial heredities, each exactly as mysterious
as the first. Thus these 60 trillions of gemmules gathered in the
egg and distributed in a precise manner are in reality only a dis-
guising of the homunculus of the ovalists. Perhaps we have no
reason to suppose that these gemmules design by their agglomeration
this invisible homunculus, but at least it is certain that they
are disposed in a manner which is in relation to the form of the
man to be determined, since in fact each of them represents not
alone a cell of the man, but a cell with the place it is to occupy.

One sees thus how complex is this system which has for its aim
the simplifying of the question of heredity: it is more logical to
consider simply the egg as having the power to produce a man than
to attribute a power as mysterious to 60 trillions of gemmules to
which it is necessary to accord, in addition, a determinative capacity

OTHER THEORIES OF SPECIES-FORMING. 225

which results in conducting each cell to exactly that place which
it ought to occupy.

In addition to the theories of an ultimate micromeric structure
of protoplasm, certain other recent hypothetical explanations of
Verworn’s bio- the special properties of protoplasm should be noted.
gen hypothesis. One is the biogen hypothesis of Verworn, the physiol-
ogist of Gottingen, one the chemism theory of Le Dantec, one
the physical machine theory of Delage, and another is the general
vital principle hypothesis of the neo-Vitalists. Verworn’s hypoth-
esis to account for the physiological activities of protoplasm, 7. e.,
the special life attributes, as assimilation, disassimilation, growth,
irritability, etc., consists in the postulation of a complex chemical
compound of unknown structure called biogen, but with the special
capacities of an enzyme. This biogen is assumed to be constantly
labile, 7. e., breaking down and rebuilding itself and by this per-
formance acting as a go-between (enzyme or perhaps katalysator)
between the atmospheric oxygen brought to the cell by the blood
and the oxidisable (food) products (also brought by the blood).
Not only can the biogen rebuild itself, but by polymerisation it can
grow, that is, increase the size of its molecules by adding side-
chains of atoms. ‘This, according to Verworn, constitutes cell
growth. This growth is not indefinite, as the atoms tend to break
away again and thus there is a limit to the size of the biogen mole-
cules. The author only presents his conception of biogen as a good
working hypothesis.

Delage has also offered a tentative physico-chemical explanation
of certain of the properties of protoplasm, as its movements, its
Delage’s ma- nutrition, and even its reducing division, on the basis
chine theory. of osmotic effects due to the constant interchange of
substance from the outer layers of the cell protoplasm to the inner
through fine membranes or special protoplasmic layers which he
assumes to enclose each cell part, 7. e., nucleus, chromosomes, etc.
Nutrition, for example, is effected according to Delage, by constant
selective osmotic exchanges between the liquid and_ semi-liquid
parts of the cell, the blood-plasm of course constantly bringing
food and carrying off excreta to and from the periphery of each
cell. Cell division is the result of mutual pulls and pushes, its
essential feature always being the actual sundering of parts; but
how this mechanical process is guided or controlled as it is, or even
initiated, is left unexplained.

Le Dantec holds that life is a chemical phenomenon. “La vie est
Le Dantec’sthe- un phénomeéene chimique, c’est-a-dire que les seuls
ory of chemism. caractéres essentiels par lesquels une action vitale
differe d’une manifestation de l’activité de la matiére brute sont rela-

7 ad
j

226 DARWINISM TO-DAY.

tifs a des destructions et des constructions d’édifices moléculaires.
Cette vérité, toute la biologie nous la prouvera de mille maniéres; il
vaut donc mieux l’énoncer en commengcant, de maniere a ce qu'elle
prenne la premiére place dans l’esprit de ceux qui se livreront a
étude des €tres vivants.

“Mais une réaction chimique n’est pas quelque chose d’isolé et
ne se produit que dans certaines conditions dont la réalisation peut
étre liée a des particularités d’ordre physique (chaleur, é€lectricité,
lumiére, etc.) ; de plus, elle s'accompagne toujours de phénoménes
accessoires qui sortent également du domaine de la chimie (chaleur,
mouvement, etc.). Ceci est vrai surtout pour les réactions des
matiéres vivantes, a cause de l'état trés spécial de ce qui représente
la solution de ces matiéres dans l’eau. La vie est aquatique, mais
les mati€res vivantes ne se dissolvent pas comme du sel marin”
(‘“‘Traité de Biologie,” pp. 43-44, 1903).

He goes on to discuss, with keen analysis and ingenious but uncon-
vincing synthesis, the various primary conditions and activities of
life, explaining each vital phenomenon separately on a basis of
chemism. He even proposes a chemical notion of species. Such
a chemical species can of course take no primary account of form,
but as conditions of chemical identity will usually involve identity
of form, the various individuals composing a chemical species will
possess a similar or identical form. An author, undertaking what
Le Dantec undertakes, must necessarily be a bold thinker and a
bold writer. The present author is both. And he is nowhere unin-
teresting or unsuggestive, but also is he nowhere wholly con-
vincing.

The position of the neo-Vitalists is perhaps best to be taken
from that of Driesch, an extremely able present-day biologist, whose
first belief was in a radical mechanical explanation of
all life phenomena, and whose brilliant experimental
work has furnished many of the examples referred to in all text-books
of the modern study of the mechanics of development. But Driesch’s
present position 1s an uncompromising belief in the impossibility
of explaining life-forms and life-functions on the basis of ever so
complex a combination of purely physico-chemical and mechanical
conditions and factors. Put positively, neo-Vitalism demands the
assumption of an extra-physico-chemical factor (called ‘“‘psychoid,”
according to Driesch’s nomenclature), which is an_ attribute
of, or essential kind of potentiality pertaining to, organised
living substance, and not found in nor influencing inorganic
bodies.

Butschli has well pointed out that neo-Vitalism is really only
a return to the old “vital principle” belief, and that we are now,

Neo- Vitalism.

OTHER THEORIES OF SPECIES-FORMING. 227

and have beep ever since our practical giving up of the vital prin-
ciple notion, making steady progress in the explanation of life-
forms and life-functions on strictly mechanical and physico-chemical
grounds. While we have by no means explained all life attributes
in this way, Biitschli holds that our progress has been such as to
make no demand for the introduction as yet of a new vital principle
under a pseudo-scientific guise.

Other neo-Vitalists, of whom _G, Wolff_is a type, lay chief stress
on the inexplicableness of the Zweckmdssigkcit in organisms by
any of the known biological facts and factors, and see in the deter-
mination or very existence of this Zweckmdssigkeit the chief revela-
tion of a vital factor, wholly distinct from anything found in the
inorganic world. Wolff's argument is clever and suggestive, and
brings home to one strongly the indissoluble relationship between
living matter and its adaptivity. In its fundamental character life
is adaptivity: the indispensable relation between living matter and
the rest of nature is the pliability, the adaptiveness of the living
matter. “Die sweckmdssige Anpassung ist das, was den Organis-
mus gum Organismus macht, was sich uns als das eigentlichste
Wesen des Lebendigen darstellt. Wir kinnen uns keinen Organis-
mus denken ohne dieses Charakteristikum. ... Und wir erkennen
dass jede Erklarung, welche das Leben voraussetzt, jede postvi-
tale Erklarung der organischen Zweckmassigkeit, in jedem
Falle voraussetzt was sie erklaren will; wir erkennen dass die
Erklarung der Zweckmassigkeit mit der Erklarung des Lebens
zusammenfallen muss.”

But perhaps there is a difference between the plastic response of
protoplasm to the varying conditions of oxygen, food, temperature,
etc., about it, so that within certain limits of external versatility it
still lives, and that extraordinary specialisation of fitness which we
see exhibited by a parasitic Sacculina with relation to its crab
host. And believers in natural selection hold that it is exactly one
of the chief glories of selection that it does explain this highly
specialised fitness. More than that, closer examination of the
phenomena of organic Nature reveals many examples of an unfit-
ness, which certainly ought not to exist if there is a special vital
principle responsible for fitness throughout the organic kingdom.
There is a moth common with us here in California, by name
Phryganidia californica, whose larve live on the leaves of the oak-
trees. Two generations appear each year. The eggs for the first
brood of caterpillars are laid in spring by the moths on the leaves
of the live-oaks and also of the white-oaks. The larve soon hatch,
feed through the summer on the leaves, and in September pupate,
the moths appearing in October. These moths now proceed to lay

228 DARWINISM TO-DAY.

the eggs for the second generation, which eggs are also deposited
on the leaves of both live- and white-oaks. But while the live-oak
is an evergreen tree, the white-oak is deciduous, and sheds its
leaves soon after these October eggs are laid on them, which means
that one-half of this second generation is doomed to die of starva-
tion immediately after hatching. This is repeated regularly each
year, and is certainly a distinctly unfit habit in this moth’s life
economy. Plate refers to a similar instance of Unsweckmdassigkeit
as follows: “As I once was landing on Santa Maria Island in the
Gulf of Aranco, the whole shore swarmed with thousands of giant
cuttlefishes (Ommatastrephes gigas) which partly lay dead on the
beach and partly were swimming around in the shallow water.
These latter instead of trying to get back into deeper water, con-
stantly swam towards the land until a breaker threw them up high
and dry. Reflexes and instincts often make mistakes, that is, they
result in actions which result in actual harm, and nothing is more
mistaken than the declaration that an organism reacts under normal
circumstances always in a way to serve the preservation of its life.
That organisms under new circumstances or in abnormal condi-
tion very often react unfitly, requires no elaboration; every light-
house against which thousands of birds and insects are killed, the
toxicological phenomena, the incomplete regeneration, every club-
foot, and every Wasserkopf prove this. The countless harmful re-
actions and incompletenesses in structure make it impossible to
speak, in the vitalistic sense, of an inherent Zweckmdssigkeit of
organisms, of a tendency always to change in the direction of use-
fulness. An organism is exactly as definitely ruled by chemico-
physical laws as every dead body. Let an organism happen in any
set of conditions: it has no longer the choice among a useful, a
harmful, or an indifferent reaction, but the causal chain determines
for a definite direction and this is, as a thousandfold observations
show, not a life-preserving one, in other words is not sweckmdssig.
If now in spite of this organisms have become, in the course of
earth-history, even more complex and more capable and have
acquired the most wonderful adaptation, there must obtain some
regulatory principle in Nature, which we, with Darwin, recognise
as actually existing in the struggle for existence and the con-
sequent selection of fit variations. If organisms actually had the
capacity to direct their vital activities always toward the side of
utility, then the workings of the natural forces would be over-
come and Mysticism again be introduced in natural philosophy.
Both actual observation and the theoretical basis of natural science
give no basis for any hypothesis of the existence in organisms of
an immanent capacity for adaptive reactions.”

OTHER THEORIES OF SPECIES-FORMING. 229

5 Weismann, A., “On Germinal Selection as a Source of Definite
Variation,” trans. McCormack, p. 3, 1896.

*T quote from Morgan, “Evolution and Adaptation,” pp. 165-166,
1903, the following special protest against the means of escape from

Morgan’s criti- 2 tight place which Weismann has taken advantage of

cism of Weis- in his dilemma: ‘Thus Weismann has piled up one
mann’s method hypothesis on another as though he could save the
of argument. integrity of the theory of natural selection by adding

new speculative matter to it. The most unfortunate feature is that
the new speculation is skilfully removed from the field of verifica-
tion, and invisible germs whose sole functions are those which
Weismann’s imagination bestows on them, are brought forward
as though they could supply the deficiencies of Darwin’s theory.
This is, indeed, the old method of the philosophisers of nature. An
imaginary system has been invented which attempts to explain all
difficulties, and if it fails, then new inventions are to be thought
of. Thus we see where the theory of the selection of fluctuating
germs has led one of the most widely known disciples of the Dar-
winian theory.

“The worst feature of the situation is not so much that Weismann
has advanced new hypotheses unsupported by experimental evi-
dence, but that the speculation is of such a kind that it 1s, from its
very nature, unverifiable, and therefore useless. Weismann is mis-
taken when he assumes that many zoologists object to his methods
because they are largely speculative. The real reason is that the
speculation is so often of a kind that cannot be tested by observa-
tion or by experiment.”

7 Roux, W., “Der Kampf der Theile im Organismus,” 1881.

® Baldwin, J. Mark, ‘““A New Factor in Evolution,” Amer. Nat.,
Vol. XXX, pp. 441 ff., 1896; see also the same author’s ‘‘Develop-

References to ment and Evolution,” chap. viii, 1902; in the appen-
discussions of dices of this book is given a detailed history of the
orthoplasy. independent formulation of the theory of “Organic
Selection or Orthoplasy,” by Baldwin, Osborn, and Morgan.

° Osborn, H. F., “A Mode of Evolution requiring neither Natural
Selection nor the Inheritance of Acquired Characters,” Trans. New
York Acad. Sci., pp. 141-148, 1896; also Science, April 3, 1896; also
Amer. Nat., Nov., 1897. From this last reference I quote the
following concise statement of the theory: “This hypothesis as it
appears to myself is, briefly, that ontogenic adaptation is of a very
profound character; it enables animals and plants to survive very
critical changes in their environment. Thus all the individuals of
a race are similarly modified over such long periods of time that,
very gradually, congenital variations which happen to coincide with

230 DARWINISM TO-DAY.

the ontogenic adaptive modifications are collected and become
phylogenic. Thus there would result an apparent but not real
transmission of acquired characters.”

*°? Morgan, C. L., “Habit and Instinct,” pp. 312 ff., 1896; see also
Science, pp. 793 ff., Nov., 1896. In Appendix C of Baldwin’s ‘‘De-
velopment and Evolution,’ p. 347, 1902, is the following clear
statement (in letter to Baldwin) of Morgan’s conception of organic
selection:

“7. On the Lamarckian hypothesis, racial progress is due to the
inheritance of individually acquired modifications of bodily struct-
ure, leading to the accommodation of the organism or race to the
conditions of its existence.

“2. This proposition is divisible into three: (a) Individual prog-
ress is due to fresh modifications of bodily structure in accommo-
dation to the conditions of life. (b) Racial progress is due to the
inheritance of such newly acquired modifications. (c) The evolu-
tion of species is the result of the cumulative series—

“a>b+a'>b’+a">b"’+a'">b'"" etc, etc., where a, a’, a”, a’ are
the acquisitions, and b, b’, b”, b’” the cumulative inherited results.

“3. Anti-Lamarckians do not accept (b) and (c). But they
accept (a) in terms of survival. No one denies that individual
survival is partially due to fresh modifications of bodily structure
in accommodation to the conditions of life.

“4. It logically follows from 3 that individual accommodation is a
factor in survival which cooperates with adaptation through ger-
minal variation.

“Weismann, following the lead of Roux, interpreted individual
modification in terms of intra-selection. He clearly saw the impli-
cation given in 4 above. Speaking of ‘the well-known instance of
the gradual increase in the development of deers’ antlers,’ he says
(Romanes Lecture, 1894, p. 18): ‘It is by no means necessary
that all the parts concerned should simultaneously adapt them-
selves by variation of the germ to the increase in size of the antlers;
for in each separate individual the necessary adaptation [accommo-
dation] will be temporarily accomplished by intra-selection—by the
struggle of parts—under the trophic influence of functional
stimulus.’

“6. So far there is no direct relation between specific modifications
and specific variations. Individual accommodation, as a factor
in survival, affords time (Weismann, op. cit., p. 19) for the occur-
rence of any variations of an adaptive nature.

“7, My own modest contribution to the further elucidation of
the subject is the suggestion (1) that where adaptive variation v
is similar in direction to individual modification m, the organism

OTHER THEORIES OF SPECIES-FORMING. 23U

has an added chance of survival from the coincidence m+v; (2)
that where the variation is antagonistic in direction to the modifica-
tion, there is a diminished chance of survival from the opposition
m—v; and hence (3) that coincident variations will be fostered
while opposing variations will be eliminated.

“8 If this be so, many of the facts adduced by Lamarckians >
may be interpreted in terms of the survival and gradual establish-
ment of coincident variations by natural selection under the
favourable environing conditions of somatic modifications.

“9. It is clear that there is nothing in this suggestion of a direct
relation between specific accommodation and coincident variation
which can be antagonistic to the indirect relation indicated above
in 6.

“to. Correlated and coexistent variations would have the same
relations to coincident variations as obtain in other cases of natural
selection.”

CHAPTER IX.

OTHER THEORIES OF SPECIES-FORMING AND
DESCENT (CONTINUED): AUXILIARY THE-
ORIES (CONTINUED).

Isolation Theories —The varying importance attributed
by different biologists to the theories explaining means
and results of isolation is notable. While by
Importance of . . . . :
the jsclation SOMe the species-forming influence of isolation
factor in species- is held to be as effective as selection itself,—
forming. : ;
some deem it more effective,—others attach but
little importance to it, indeed see no effects of consequence.
These latter men are likely to be morphologists, cytologists,
and laboratory men generally; the former are systematists,
students of distribution, and so-called field naturalists. Thus
Delage, who gives much attention in his general discussion
of the theories of heredity, variation, and species-forming
to many purely speculative theories of the ultimate structure
and behaviour of protoplasm, and of the mechanism of
heredity, dismisses the whole subject of geographic and
topographic isolation with a couple of superficial para-
graphs, in which he presents a singularly fallacious state-
ment of what the effects of isolation should be. On the
other hand the veteran German world-voyager and exploring
naturalist, Moritz Wagner, established long ago, on the basis
of his observations and deductions, a “law”’ of species-form-
ing by migration and consequent isolation, which in his mind
makes the natural selection theory superfluous. And Henry
Seebohm in a discussion of Romanes’s* formulation of the
principle of physiological selection, says: “So far as is
232

OTHER THEORIES OF SPECIES-FORMING. 233,

known, no species (of birds) has ever been differentiated.
without the aid of geographical isolation, though evolution.
may have gone on to an unknown extent; and, so far as we:
can judge, geographical isolation must always, sooner or
later, be followed by differentiation.” And Romanes, him-
self, conspicuous as the only pupil and disciple of Darwin
personally advised and aided by the master himself, and one
of the most brilliznt upholders and expositors of Darwin-
ism, says:’ “Indeed I believe with Mr. Gulick, that in the
principle of isolation we have a principle so fundamental
and so universal, that even the great principle of natural
selection lies less deep and pervades a region of smaller
extent. Equalled only in its importance by the two basal
principles of heredity and variation, this principle of isola-
tion constitutes the third pillar of a tripod on which is reared
the whole superstructure of organic evolution.” Thus the
most ardent believers in the effects of isolation find it, inde-:
pendent of selection and alone, sufficient to explain species-
forming, while the most ardent neglecters of isolation theo-
ries find them too slight to be of any consequence at all. We
shall take middle ground and find in isolation a factor of
great effectiveness and one wide-spread in its influence in
helping to produce the present-day status of the animal
kingdom, but yet a factor which shall most fairly be looked
on as an auxiliary or helping-theory of natural selection. In
fact, to my mind, the proof of the species-establishing effects
of isolation, and of the actual existence of isolation (proof
of means or modes of isolation), is something much needed
by the general natural selection theory for its own sup-
port. Selection needs help from isolation. To my mind,
also, these means of isolation actually exist, and the result-
ing isolation is actually a very potent factor in species-form-
ing. The proofs seem to me obvious.

The name isolation fairly well defines the condition that
we are to discuss; (the term segregation has also been used.

234 DARWINISM TO-DAY.

by some authors to name the same condition). 11, in a
species, a number of individuals show a certain congenital
variation, this variation will probably be lost by
cross-breeding with individuals not having it,
unless the individuals having it are in the ma-
jority or unless they become in some way isolated from the
others and segregated so that they will breed among them-
selves. By such isolation and such in-and-in breeding the
newly appearing congenital variations might soon become
established, and if advantageous be so considerably developed
as soon to distinguish as a variety or incipient species the
members of the isolated colony. With time a distinct new
species might result. Are there means to produce such isola-
tion of groups of individuals belonging to a common species?
The answer to this is certainly an affirmative one. There
seem to be, indeed, several means of producing isolation,
a and the isolation may be variously named ac-
of effecting iso- cordingly. Undoubtedly the most important of
meio these kinds of isolation, at least in the light of
our present knowledge, is that known as geographical or
topographical isolation. Isolation produced in other ways
may be called biologic or physiologic or sexual isolation.
In the case of geographic or topographic isolation the iso-
lated group or groups of individuals are actually in another
region or locality from the rest of the species, this being
the result of migration, voluntary or involuntary. In bio-
logic isolation the individuals of the species all inhabit the
same territory but become separated into groups by struc-
tural or physiological characters which prevent

Weick aa ae miscellaneous inter-breeding. The real founder
theory of species- and most insistent upholder of the theory of
mast oe. species-forming by isolation (geographic and
topographic isolation), was Moritz Wagner *
(1813-1887), a traveller and naturalist, whose wanderings
and observations brought to him the conviction that while

What is meant
by isolation.

OTHER THEORIES OF SPECIES-FORMING. 235

natural selection might modify species and even produce
continuous evolution it could never differentiate species,
that is, produce new species. It could never, in Wagner’s
belief, produce the actual condition which we know to exist
in the present-day and past (now extinct) animal kingdom,
this condition being the existence of hosts of distinct, though
related, animal species or kinds. Wagner’s travels included
journeys to North, Central, and South America, West Asia,
and North Africa. His first clear enunciation of his theory,
in which pronouncement he took definite stand against
the claimed capacity of Darwinian selection to produce new
species, was in 1868, in a paper read in Munich, entitled
“Die Darwinische Theorie und das Migrationsgesetz der
Organismen.” From the time of the appearance of this
first paper until within a year or two of his death, Wagner
steadily wrote and fought for his theory, but without gain-
ing for it any such wide or authoritative acceptance as he
hoped. In a letter dated August 30, 1884, Wagner pathet-
ically writes, “Ich sterbe mit der Uberzeugung, dass man
dies wenigstens nach meinem Tode anerkennen wird.”
Wagner’s theory included not only the characteristics
already pointed out as the basis of all theories of the influ-
ence of isolation in species-forming, but the assumption that
all species of animals have a strong tendency, or are con-
stantly attempting, to “spread out’’; that is, have a driving
instinct of migration and dispersal. The basis of this
tendency is undoubtedly the overcrowding in the immature
stages and in times of short food-supply or untoward exter-
nal conditions of temperature, humidity, etc. This tendency

to movement is Wagner’s “Migrationsgesetz,” and the out-

come of it is to bring about conditions of topographic and
geographic isolation among all kinds of animals. While in
his first papers Wagner looked on his theory as a sort of
supporting or auxiliary theory to that of natural selection,
he soon began to see in it, calling it now by the name of

236 DARWINISM TO-DAY.

“Separationstheorie,” an independent and alternative expla-
nation of species-forming. In 1870, he wrote:* “Um den
Unterschied beider Theorien moglichst kurz auszudrticken :
nach der Darwin’schen Selectionstheorie ziichtet die Natur
in Folge des Kampfes ums Dasein rastlos neue typische
Formen der Organismen durch Auslese ntitzlicher Varieta-
ten, gleichviel ob inner- oder ausserhalb des Verbreitungs-
gebietes der Stammart, und kann diesen Prozess der Bil-
dung einer neuen Art nur innerhalb eines sehr ees
Zeitraumes vollziehen.

“Nach der Separationstheorie ziichtet die Natur nur
periodisch neue Formen stets ausserhalb des Wohngebietes:
der Stammart durch geographische Isolierung und Kolo-
nienbildung, ohne welche bei allen héheren Tieren getrenn-
ten Geschlechts keine konstante Varietat oder neue Art.
entstehen kann. Der Gestaltungsprozess einer neuen Form.
kann nicht von langer Dauer sein.”

Or in still more condensed form: . . . “Nach der Selek-
tionstheorie ist der Kampf ums Dasein, nach der Separa-
tionstheorie die ratumliche Absonderung, die nachste zwing-
ende Ursache der Artbildung.”

Wagner's latest, most definitive, cleanest cut, single
formulation of the Separationstheorie is that contained in
two paragraphs in his essay entitled, “Leopold von Buch
und Charles Darwin” (Kosmos, 1883). These paragraphs
are the following:

“1. Jede dauernde ratimliche Absonderung einzelner oder
weniger Emigranten von einer Stammart, welche noch im
Stadium der Variationsfahigkeit steht, erzwingt auf Grund
der Variabilitat und der Vererbung eine konstante Diffe-
renzierung, indem sie unter Mitwirkung veranderter Le-
bensbedingungen, die jeden Standortswechsel begleiten,
auch die minimalsten individuellen Merkmale der ersten
Kolonisten bei blutsverwandter Fortpflanzung fortbildet
und _ befestigt.

OTHER THEORIES OF SPECIES-FORMING. 237.

“2. Keine konstante Varietat oder Art entsteht ohne
Ausscheidung einzelner oder weniger Individuen von der
Stammart und ohne Ansiedelung an einem neuen Standort,
weil Massenkreuzung und Gleichheit der Lebensbedin-
‘gungen in einem zusammenhangenden Wohngebiet immer
absorbierend und nivellierend wirken mussen und indivi-
duelle Variationen stets wieder in die Stammform zurtck-
drangen.”

Wagner’s ° long series of interesting papers and addresses
are crammed with facts of plant and animal geography,

taxonomy and paleontology, and with keen interpretation
of these facts, and clear and incisive formulations of his few

generalisations,

One of the most ardent present-day upholders of the
‘species-forming potency of geographical isolation is David
Starr Jordan, the foremost American student of the classi-
fication and distribution of fishes. From a recent paper’
I abstract the following brief statements of his beliefs con-
‘cerning the character and results of the influence of geo-
graphical isolation.

“It is now,” writes Jordan, “nearly forty years since
Moritz Wagner (1868) first made it clear that geographical

isolation (raumliche Sonderung) was a factor
Jordan on

geographic or condition in the formation of every species,

aBUIRHGR: race, or tribe of animal or plant we know on

the face of the earth. This conclusion is accepted as almost
self-evident by every competent student of species or of
the geographical distribution of species. But to those who
approach the subject of evolution from some other side the
principles set forth by Wagner seem less clear. They have
never been confuted, scarcely even attacked, so far as the
present writer remembers, but in the literature of evolution
of the present day they have been almost universally ignored.
Nowadays much of our discussion turns on the question of
whether or not minute favourable variations would enable

238 DARWINISM TO-DAY.

their possessors little by little to gain on the parent stock,
so that a new species would be established side by side with
the old, or on whether a wide fluctuation or mutation would
give rise to a new species which would hold its own in com-
petition with its parent. In theory, either of these condi-
tions might exist. In fact, both of them are virtually un-
known. In nature a closely related distinct species is not
often quite side by side with the old. It is simply next to it,
geographically or geologically speaking, and the degree of
distinction almost always bears a relation to the importance
or the permanence of the barrier separating the supposed
new stock from the parent stock.

“A flood of light may be thrown on the theoretical prob-
lem of the origin of species by the study of the probable
actual origin of species with which we may be familiar, or
of which the actual history or the actual ramifications may
in some degree be traced.”

Dr. Jordan then proceeds to relate and analyse our pres-
ent actual knowledge of the make-up of certain local faune,.
of the migrations and distribution of certain well-known
animal species (especially in the phyla of birds and fishes,
in which groups our knowledge of the present status in
North America of species and varieties and their distribu-
tion is nearly exhaustive), and of the climatic, topographic,
and general geographic barriers ° which determine this dis-
tribution, in a way most convincing to unprejudiced minds.
_ He brings to the support of his own statements of fact and
opinion the testimony (contained in personal letters an-
swering direct queries from himself) of many well-known
American students of systematic and faunistic zoology.
Jordan sums up the results of his display of North Ameri-
can faunal conditions in various paragraphs, from among
which the following are quoted:

“In regions broken by few barriers, migration and inter-
breeding being allowed, we find widely distributed species,

OTHER THEORIES OF SPECIES-FORMING. 239

homogeneous in their character, the members showing indi-
vidual fluctuation and climatic effects, but remaining uni-
form in most regards, all representatives slowly changing
together in the process of adaptation by natural selection.
In regions broken by barriers which isolate groups of indi-
viduals we find a great number of related species, though in
most cases the same region contains a smaller number of
genera or families. In other words, the new species will be
formed conditioned on isolation, though these same barriers
may shut out altogether forms of life which would invade
the open district.

“Given any species in any region, the nearest related
species is not likely to be found in the same region nor in
a remote region, but in a neighbouring district separated
from the first by a barrier of some sort.

“Doubtless wide fluctuations or mutations in every species
are more common than we suppose. With free access to the
mass of the species, these are lost through interbreeding.
Isolate them as in a garden or an enclosure or on an island,
and these may be continued and intensified to form new
species or races. Any horticulturist will illustrate this.

“In these and in all similar cases we may confidently
affirm: The adaptive characters a species may present are
due to natural selection or are developed in connection with
the demands of competition. The characters, non-adaptive,
which chiefly distinguish species do not result from natural
selection, but from some form of geographical isolation and
the segregation of individuals resulting from it.

“In the animal kingdom, generally, we may say: When-
ever a barrier is to some extent traversable, the forms
separated by it are liable to cross from one side to the other,
thus producing intergradations, or forms more or less
intermediate between the one and the other. For every
subspecies, where the nature of the variation has been care-
fully studied, there is always a geographical basis. This

240 DARWINISM TO-DAY.

basis is defined by the presence of some sort of a physical
barrier. It is extremely rare to find two subspecies inhabit-
ing or breeding in exactly the same region. When such
appears to be the case, there is really some difference in
habit or in habitat ; the one form lives on the hills, the other
in the valleys; the one feeds on one plant, the other on
another; the one lives in deep water, the other along the
shore. There can be no possible doubt that subspecies are
nascent species, and that the accident of intergradation in
the one case and not in the other implies no real difference
in origins.

“To the general rule that closely allied species do not live
together there exist partial exceptions. It may be well to
glance at some of these, for no rule is established until its
exceptions are brought into harmony with the phenomena
which illustrate the rule.’ (Here Dr. Jordan details the
facts of distribution in three cases from among the fishes,
which apparently form exceptions to his general rule).

As an example of the effects of an unusual and interesting
phase of isolation I may refer to the conditions noted con-

See cerning the distribution and species distinction
isolation inthe Of the Mallophaga, a group of small wingless
Mallophaga. = insect parasites on birds and mammals. These
parasites live for their whole lives among the feathers or
hair of their hosts, and while able to run swiftly are unable
to fly and thus to migrate freely from bird to bird.

“There are to be noted various results of the influence on
the taxonomy of the Mallophaga of the peculiar conditions
of their parasitic life. While the uniformity and persistence
of the conditions under which the life of the parasites is
passed tend to preserve with little change the species types,
the peculiar isolation, often pretty complete, of groups of
individuals of a parasite species on individual birds of the
host species and the consequent close breeding, tend to
foster and fix those inevitable slight variations always mani-

isolation studied

OTHER THEORIES OF SPECIES-FORMING. 241

fest in a comparison of offspring and parents, but under
normal conditions held in check or lost (unless directly
advantageous) by crossing among less closely related indi-
viduals. For example, the individuals of a parasite species
on a bird of long life and non-gregarious and monogamous
habits, like an eagle, live very much the life of an isolated
community. There must be many years of in-and-in breed-
ing. It is like island life. The result is certain: the members
of this isolated group will soon differ from the specific
type in noticeable particulars. On the other hand, the con-
ditions of life on this ‘island’ are practically identical with
the conditions on other similar ‘islands’—other eagles—in-
habited by other individuals of the same parasite species, so
there is no influence working to produce a wide divergence
of the members of these various isolated groups of indi-
viduals of the same species. Now this isolation of groups of
individuals is in some degree an incident of the life of all
Mallophaga ; in some instances it is considerable; in others,
inconsiderable, but taken altogether a condition in the life
of the whole order exerting an influence which has the
readily recognisable result of creating a great number of
small variations within species limits.

“The results, manifest to any student of the group, of
these two opposing influences are to render difficult the divi-
sion of the order into distinct genera on account of the gen-
eral similarity of structure, and to make difficult the defini-
tion of species on account of the many slight variations
among the individuals from different bird individuals.” *

The study of geographic distribution and its influences on
species-forming has not been limited, of course, to living

Geographic Organisms alone. In fact, the geologic study
igh eat of distribution and migration of both animals
animals, and plants has given us some of our most
important facts touching the problem of the influence of
isolation on species-transformation. In an interesting paper

242 DARWINISM TO-DAY.

on the “geological study of the migration of marine inverte-
brates,” Smith *° has pointed out the general principles and
conditions upon which the interpretation of the geographic
distribution of the marine invertebrates of the earlier geo-
logic ages must be based.

In closing this consideration of the status of geographic
isolation as a factor in species-forming, I should not omit to

Isolation not Call attention to the fact, which should be obvi-
ee. ous enough to any reader, that isolation in itself
forming. cannot be the basic and all-sufficient cause for
the production of specific differentiation, any more than any
selective factor can. The prerequisite in both cases is the
occurrence of variation. What are the variations, and how
are they produced: these are the fundamental questions in
species-forming. Isolation is a tremendously favouring con-
dition but not a primary cause of species-forming. It tends
to help along, to hurry up species disintegration, not to
initiate it. It is a biological catalytic agent. —

In this present connection the pertinent question is, is the
influence of geographical isolation in the cumulation of
variation or intra-specific differentiation due to its com-
pelling in-and-in breeding and hence the fostering and cumu-
lation of fortuitous Darwinian variations occurring in the
comparatively few individuals of the isolated group, or is
there a spur to variation, or even actual production of it along
determinate lines, in the new environmental conditions com-
mon to all the isolated group but inevitably different from
the conditions to which the parent type is exposed? Is there
a gradual accumulation of differences between the split-off
group and the parent group due to environmental influence
plus in-and-in breeding? If we could reply yes to this
question, we should have a sufficient explanation of
how the isolated group splits rapidly away in many

small, and in a few large, characteristics from the parent.

stock.

OTHER THEORIES OF SPECIES-FORMING. 243

From the foregoing it is obvious that geographical isola-
tion is a proved, effective, and widely applied species-form-
ing factor. So much cannot be said for biologic
and sexual isolation.” The actual existence of
such isolation is not proved by any mass of evi-
dence based on observation, although the theory is by no
means pure speculation; nor are the results of such isola-
tion clearly indicated, although a certain amount of observa-
tion and experimental evidence can be adduced to show
them. The different phases of isolation, not geographic,
called by different names, as biologic, physiologic, sexual,
and morphologic isolation, all have reference to some sort
of segregation of individuals of the same species into groups
inside of each of which mating takes place, and among
which little or no cross-breeding occurs, because of varying
habits, or unusual sexual aversion or attraction, or physio-
logical or morphological variation affecting mating. For '
example, to take first a sort of combination of geographic
and biologic isolation, Plate*” points out that there are
twelve species of albatrosses in the southern hemisphere, of
which nine or ten belong to the Australian zoo-geographical
realm and intermingle throughout most of their range. At
breeding time, however, these different species become
segregated in restricted and separate localities so that mating
is alwayS accomplished among different individuals of the
same species, although hybridisation could doubtless obtain
successfully among these closely related albatross forms.
Thus the species characters are kept pure; the species dis-
tinct.

An example of pure biological isolation and one within
a single species (which is the sort of isolation we are more

Anexampleof interested in) might be produced in the follow-
Aaa ing way. We know of numerous species of
work, butterflies which appear in different seasons of
the year in different colour-pattern. This is not a colour

Biologic
isolation.

244 DARWINISM TO-DAY.

change in individuals but results from an earlier or later
hatching of eggs laid in the autumn or summer before.
These eggs may, indeed, be all of one batch or lot, laid by a
single female. Some of these eggs hatch in the spring; the
butterflies that come from these spring larve are of one col-
our-pattern ; some of the eggs, however, delay hatching until
summer; from these larve come butterflies of another
colour-pattern; some of the eggs even go over until fall
before hatching; these latest butterfly individuals may be of
a third colour-pattern. The colour-pattern here must have
some fixed relation to the time or season of hatching of the
eggs; it is not a result of isolation. But the condition well
illustrates the actual existence of a biological isolation within
a species: the spring butterflies must mate among them-
selves, the summer individuals among themselves, and the
fall butterflies among themselves. Within the one species
are three biologically isolated groups of individuals re-
strained from inter-breeding. Suppose the individuals of
a bird species show among themselves a tendency to vary
in their breeding time; some are ready to breed early, others
delay mating. Roughly segregated into two groups, early
breeders and late, the individuals of the two groups would
obviously tend to breed each inside its own group. Hut-
ton ** actually records the occurrence of two varieties of the
shore-bird, Céstrelata neglecta, in the Kermadec Islands,
which live together but breed at different times. A pelagic
crustacean living near the shore increases rapidly in num-
bers; some individuals find themselves able to live on the
shore in pools between tide-lines. The pool dwellers breed
together: the pelagic individuals breed together; a biologic
isolation—in truth an isolation partly topographic—might
soon come to exist. Any variation in habits of life among
individuals living in the same locality, which tends to deter-
mine that breeding shall be roughly restricted within cer-
tain groups produces biologic isolation ; such variation might

OTHER THEORIES OF SPECIES-FORMING. 245

be a variance in sexual maturity, a change in breeding time
for that or any other reason, a tendency on the part of cer-
tain individuals to live more or less concealed in holes, under
stones, etc., changes in food-habits, as the gradual going
over of some individuals of a plant-feeding insect species
from the old food-plant to a new one, or the tendency within
an omnivorous species for groups to restrict themselves to
certain specific foods: all such variations might lead to pos-
sible biological isolation.

By sexual isolation authors usually refer to the influ-
ence of some variation tending to make difficult or impossi-

Seenal ble wholly free and miscellaneous mating or
isolation. breeding inside of a species. This variation
may be of purely physiological character or may be a struc-
tural one: that is, the hindrance to mating may be one of
instinctive feeling, a “race-feeling’’ depending on an antipa-
thy to odour, to age, to appearance, etc., or may be a slight
modification of the copulatory organs making such mating
difficult, or even a modification of the egg or the spermato-
zoids making fertilisation difficult. It is a well-known fact
that numerous varieties of domesticated animal species
rarely breed together, although quite able to, and provided
with full opportunity. On the other hand, animals of differ-
ent species which in Nature rarely or never breed together
may, if kept long in confinement, as in zoological gardens,
mate ** and produce young. In each case there seems to be
question of a “race-feeling”:; in the first case a sexual
aversion keeping apart individuals of the same species, in
the second the breaking down of race-feeling that in Nature
has sufficed to prevent hybridising. This might be termed
physiological isolation, or, indeed, physiological selection, as
it has been called, and given much credit for
species-forming by Romanes’** and_ others.
Romanes and Hutton believe that a progressive
infertility results in this way (and also by the way referred

Physiological
selection,

246 DARWINISM TO-DAY.

to in the next paragraph) which can soon result in complete
infertility, hence specific distinctness on the part of the
mutually infertile groups.

Mutual infertility due to morphological variations has
been called “mechanical selection” by Karl Jordan,” and
may rest on slight variations in germ-cells or
copulatory structures. Such morphological
variations of the reproductive organs have been
believed to be shown for butterflies and spiders, while the
delicate tropismic responses of the active spermatozoids to
the attracting chemical substances in the egg-cells of echino-
derms, ccelenterates, molluscs, and fishes have been thought
to be conditions in which a slight chemical or physical varia-

Mechanical
selection.

tion might have a large influence in preventing or insuring
fertilisation. Indeed, when one examines comparatively the
curiously various complex accessory reproductive organs
(claspers, gonapophyses, intromittent organs, etc.) of almost
any group of insects, one’s first thought is that this variety
must practically effectually exclude all possibility of hybri-
dising. But the interesting detailed comparative studies
by Snodgrass ** of the accessory genitalia in various families
of Diptera make this confidence less certain. In the large
family Tipulidae, for example, he finds great complexity
and remarkable variety (among the different closely allied
species) in this complexity in the genitalia of the males, but
almost no variation at all in the corresponding (complement-
ary) parts of the females. “Throughout the entire family
the females present one type of structure, of which there is
but little modification, and certainly none to correspond with
the great variety of specific differences found in the genitalia
of the males.” Now while the great variety of the copula-
tory parts would be extremely significant if shared by both
sexes so that only one kind of key could fit one kind of lock,
we have the inexplicable condition actually existing of the
keys being extremely various and complex, but the locks all

OTHER THEORIES OF SPECIES-FORMING. 247 ©

being so similar and simple that any bent nail is able to pick
them.
Seebohm ** criticises Romanes’s theory of physiological
selection, which should better be called physiological
Seebohm’s isolation, as demanding an almost impossible

oes coincidence of conditions to make it work.
physiologic se- : ; A
lection. Formulated as nearly as it can be in a single

sentence, Romanes has defined physiological selection as
follows: “Wherever, among all the possible variations of
the highly variable reproductive system there arises toward
any parent form any degree of sterility which does not
extend to the varietal form, there a new species must neces-
sarily take its origin.’”’ Seebohm points out that this is
exactly a condition that can rarely, if ever, occur, for to
bring it about we must presuppose :—

“tst. The special variation of the reproductive organs
must occur in two individuals, otherwise the possible an-
cestor of the new species would leave no descendants.

“ad. It must occur at the same time in both.

“2d. It must occur at the same place.

“ath. The two individuals must be of opposite sexes.

“sth. They must each of them possess some other varia-
tion, or their progeny would not differ from that of the rest
of the species.

“6th. The variation must be the same in both or appear
simultaneously in the majority of their children, otherwise
it would be swamped by interbreeding within the physio-
logically isolated family.”

Romanes’s theory has also been strongly criticised by
Wallace ** and by Karl Jordan.** Wallace contends that

Biles Apa DO form of infertility or sterility between the
ofRomanes’s individuals of a species can be increased by
as natural selection unless correlated with some
useful variation, while all unfertility not so correlated has a
constant tendency to effect its own elimination. But the

248 DARWINISM TO-DAY.

opposite property, fertility, is of vital importance to every
species, and gives the offspring of the individuals which
possess it, in consequence of their superior numbers, a
greater chance of survival in the battle of life. It is, there-
fore, indirectly under the control of natural selection, which
acts both for the self-preservation of fertile and the self-
destruction of unfertile stocks—except always, as correlated
above, when they become useful and therefore subject to be
increased by natural selection.” Jordan maintains that the
outcome of physiological selection can be at best only
dimorphism, not specific distinctness.

Vernon ** has formulated a theory which he calls that of
“reproductive divergence,” in the following words: “Sup-

Vernon's posing that among the members of any species
theory ofrepTo- those individuals more alike in respect to any
ductive diver-

gence. different characteristic, such as colour, form, or
size, are slightly more fertile inter se than less similar indi-
viduals, it necessarily follows that in the course of succeed-
ing generations the members of this species will diverge
more and more in respect to the characteristic in question,
whereby ultimately the original species may be split up into
two or more fresh species.” As a concrete example, Vernon
supposes that in the Lepidopterous Jthania urolina, a certain
insect found in the Amazon Valley, small individuals were
slightly more fertile with other small individuals than with
large individuals, while these were also more fertile inter se;
“then it would follow that fewer individuals of intermediate
size would be produced, and in course of time the species
would be split up into a small and large variety. These
varieties would continue to diverge as long as the process
of ‘reproductive divergence’ was acting, till at length they
might become differentiated in the two mutually sterile
species. Supposing on the other hand this variation in
fertility were correlated with slight differences of colour,
then in course of time varieties differing in respect of colour

OTHER THEORIES OF SPECIES-FORMING. 249

would be produced; or if it were correlated with both size
and colour, varieties differing in respect of both characters
might be produced. As a matter of fact, this insect does
actually occur as four distinct varieties differing in colour,
form, and size, though whether in consequence of the oper-
ation of reproductive divergence it is of course impossible
to say.” But this theory has been strongly criticised by
Karl Jordan,** who believes himself able to show that re-
productive divergence would not work in the way conceived
by Vernon, but actually in such a way as to establish an
intermediate form.

Karl Pearson ** has formulated a theory called “reproduc-
tive selection” which he believes to be distinct from both the

Peta Romanes and the Vernon theories, and to which
theory of repro- he attributes an importance in evolution “equi-
ductive selection. tent to natural selection, if indeed it be not
prepotent.”’ The theory is based on correlations which seem
to exist between the variation in some particular organ and
fertility. From studies of variation of height in 4,000 Anglo-
Saxon families and 1,182 Danish families, Pearson finds
that there exists a distinct correlation between fertility and
height in the mothers of daughters in these families. The
effect of this correlation is to render women less variable
and to raise their mean height. The quantities are small,
but are sufficient, if unchecked by natural selection, to raise
the mean height of women in forty generations by 3 1-4
inches. “A factor which would alter stature by about three
inches in I,000 years is clearly capable of producing very
considerable results in the long periods during which evolu-
tion may be supposed to have been at work.”

Of large importance in any consideration of the relations.

Gulick’sim- Of isolation to species-forming are the observa-
portant observa tions and conclusions of Gulick. Derived origi-
sions. nally from an exhaustive study of the variation
and life-conditions of certain land shells (Achatinellidz)

250 DARWINISM TO-DAY.

in the Hawaiian Islands, he formulated, in 1872, an im-
portant principle concerning the species-differentiating ef-
fects of indiscriminate isolation. As Romanes ** well points
out, isolation may not only admit of degrees, that is,
may be either total or partial, and, if partial, may occur
in numberless grades of efficiency, but it may be either dis-
criminate or indiscriminate. If it be discriminate, the isola-
tion has reference to the resemblance of the separated indi-
viduals to one another ; if it be indiscriminate, it has no such
reference. For example, if a shepherd divides a flock of
sheep without regard to their characters, he is isolating one
section from the other indiscriminately ; but if he places all
the white sheep in one field and all the black sheep in another
field, he is isolating one section from the other discriminately.
Or, if geological subsidence divides a species into two parts,
the isolation will be indiscriminate; but if the separation be
due to one of the sections developing, for example, a change
of instinct determining migration to another area, or occu-
pation of a different habitat on the same area, then the isola-
tion will be discriminate, so far as the resemblance of instinct
is concerned. Discriminate isolation has been called by
Gulick segregate breeding, and indiscriminate isolation sepa-
rate breeding.

Now the effectiveness of discriminate isolation or segre-
gate breeding, however effected, to produce species-differ-
entiation is of course obvious. In fact, as Romanes points
out, it is only when assisted by some form of discriminate
isolation which determines the exclusive breeding of like
with like, that heredity can make in favour of change of
type or lead to what we understand by organic evolution.
But what about indiscriminate isolation? Does it not seem,
at first sight at least, that this kind of isolation must count
for nothing in the process of evolution? Is it not apparently
self-evident that the farmer who separated his stock into two
or more parts indiscriminately, would not effect any more

OTHER THEORIES OF SPECIES-FORMING.,. 25f

change in his stock than if he had left them all to breed
together ?

“Well,” says Romanes, “although at first sight this seems
self-evident, it is in fact untrue. For, unless the individuals
which are indiscriminately isolated happen to be a very large
number, sooner or later their progeny will come to differ
from that of the parent type, or unisolated portion of the
previous stock. And, of course, as soon as this change of
type begins, the isolation ceases to be indiscriminate: the
previous apogamy [indiscriminate isolation] has been con-
verted into homogamy [discriminate isolation], with the
usual result of causing a divergence of type. The reason
why progeny of an indiscriminately isolated section of an
originally uniform stock—e. g., of a species—will eventually
deviate from the original type is, to quote Mr. Gulick,”’ as
follows: “No two portions of a species possess exactly the
same average character, and, therefore, the initial differ-
ences are for ever reacting on the environment and on each
other in such a way as to ensure increasing divergence as
long as the individuals of the two groups are kept from
intergenerating.”’

Gulick was led to his recognition of the principle in ques-
tion, not by any deductive reasoning from general principles,

Belin sad: but by his own particular and detailed observa-
iesof Hawaiian tions of the land mollusca of the Sandwich
land-snails, = Tslands. Here there is an immense number
of varieties belonging to several genera; but every variety
is restricted, not merely to the same island, but actually
to the same valley. Moreover, on tracing this fauna
from valley to valley, it is apparent that a slight varia-
tion in the occupants of valley 2 as compared with those
of the adjacent valley 1, becomes more pronounced in
the Wext valley. 2, “still more so: in 4,etc,,ete. Thusit
was possible, as Mr. Gulick says, roughly to estimate the
amount of divergence between the occupants of any

252 DARWINISM TO-DAY.

two given valleys by measuring the number of miles be-
tween them.

On the basis of his detailed observations, Gulick’® has
proposed the following three general propositions as to the
relations of isolation to species-forming:

“rt. A species exposed to different conditions in the differ-
ent parts of the area over which it is distributed, is not
represented by divergent forms when free inter-breeding
exists between the inhabitants of the different districts. In
other words, diversity of natural selection without separation
does not produce divergent evolution.

“2. We find many cases in which areas, corresponding in
the character of the environment, but separated from each
other by important barriers, are the homes of divergent
forms of the same or allied species.

‘3. In cases where the separation has been long continued,
and the external conditions are the most diverse in points
that involve diversity of adaptation, there we find the most
decided divergences in the organic forms. That is, where
separation and divergent selection have long acted, the re-
sults are found to be the greatest.

“The first and second of these propositions will probably
be disputed by few, if by any. The proof of the second is
found wherever a set of closely allied organisms is so dis-
tributed over territory that each species and variety occu-
pies its own narrow district, within which it is shut by bar-
riers that restrain its distribution, while each species of the
environing types is distributed over the whole territory.
The distribution of terrestrial molluscs on the Sandwich
Islands presents a great body of facts of this kind.”

Finally in a recent exhaustive discussion of the subject *’
of the relation of isolation to evolution Gulick declares that
“the whole process of bionomic evolution, whether progres-
sive or retrogressive, whether increasingly ramified and
divergent, or increasingly convergent through amalgama-

OTHER THEORIES OF SPECIES-FORMING. 253

tion, is a process by which the limitations of segregate breed-
ing are either set up and established or cast down and
obliterated.”

APPENDIX.

* Seebohm, Henry, “Physiological Selection,” p. 12, 1886.

2 Romanes, G. J., “Darwin and After Darwin,” Vol. III. p. 1, 1897.

® Wagner, Moritz, “Die Entstehung der Arten durch Raumliche

Referencesto onderung,” 1889. This book is made up of the
discussions of collected papers of Wagner, printed originally in the
isolation. time from 1868-1886, mostly in the journal Kosmos.

* Wagner, Moritz, “Uber den Einfluss der geographischen Isolie-
rung und Kolonienbildung auf die morphologischen Veranderungen
der Organismen,” July, 1870.

° Wagner, Moritz, “Uber die Entstehung der Arten durch Abson-
derung,” Kosmos, 1880.

®Haacke in his “Grundriss der Entwicklungsmechanik,”’ 1897,
gives, on pp. 335-336, an excellent summary statement of Wagner’s
position, as follows:

“Wenn wir eine Tierart bis an die Grenze ihres Verbreitungs-
gebietes verfolgen und diese Grenze wberschreiten, so stossen wir

Haacke’s sum- gewOhnlich sehr bald, und oft schon, ehe wir die
mary of Wag- Verbreitungsgrenze der betreffenden Art erreicht
ner’s theory. haben, auf eine andere, und zwar auf eine mit der
ersteren nachstverwandte Tierart, die aber ein anderes Verbreitungs-
areal inne hat. Gehen wir auch tiber das Gebiet dieser letzteren
Art hinaus, so konnen wir auf eine dritte, vierte und ftinfte Art
stossen, von denen jede den beiden ersten verwandt sein kann und
ein besonderes Verbreitungsgebiet bewohnt. Im allgemeinen kon-
nen wir den Satz aufstellen, dass es keine zwei nachstverwandten
Tierarten giebt, deren Verbreitungsgebiete sich vollkommen decken.
Vielfach kann der Fall festgestellt werden, dass die Verbreitungsge-
biete zweier nachstverwandter Tierarten sich teilweise decken; aber
eine vollkommene Deckung ist noch in keinem Fall bei zwei oder
mehr nachstverwandten Tierarten festgestellt worden. ‘Es kann
auch vorkommen, dass das Verbreitungsgebiet der einen Art voll-
standig innerhalb desjenigen der andern Art liegt, das also, soweit
der Wohnkreis der ersten Art reicht, ein Zusammenfallen mit dem
Verbreitungsgebiet der zweiten Art stattfindet; aber in solchen
Fallen dehnt sich eben die Heimat der einen Art tber die der
zweiten aus, so dass von Kongruenz der beiderseitigen Wohnge-
biete nicht die Rede sein kann. Nachtsverwandte Tierarten sind

254 DARWINISM TO-DAY.

ketten- oder, besser gesagt, netzfOrmig tiber die Erde verbreitet.
Wie die Maschen eines Netzes reihen sich die Wohngebiete der
Arten einer Gattung aneinander, und wenn auch, wie schon hervor-
gehoben, mancherlei teilweise Deckungen vorkommen, so hat sich
noch in allen Fallen, wo man die Grenzen der Verbreitungsgebiete
nachstverwandter Arten festgestellt hat, die Thatsache ergeben, dass
keine vollkommene Deckung § stattfindet. Aus dieser Thatsache
konnen wir den Schluss ziehen, dass in einem und demselben
Gebiete, soweit wenigstens alle Individuen unter denselben Ver-
haltnissen leben, aus einer Art nicht zwei oder mehr neue Arten
werden koOnnen. Wagner meinte zuerst, dass hierbei die Moglich-
keit einer allseitigen Kreuzung, wie sie nach ihm innerhalb eines
und desselben Wohnkreises einer Art moglich sein soll, eine grosse
Rolle spielt. Er hat ubrigens seine Ansichten im Laufe der Zeit
geandert und es ist deshalb notwendig, auf die Entwickelungs-
geschichte seiner Ideen etwas naher einzugehen. Ursprtinglich
suchte Wagner seine Theorie mit der Darwin’schen zu vereinigen.
Nach der letzteren entsteht eine neue Art dadurch aus einer
vorhandenen, dass die Lebensbeeinflussungen andere werden, und
dass nunmehr diejenigen Individuen seitens der ztichtenden Natur
ausgewahlt werden, die den neuen Lebensbeeinflussungen am
besten entsprechen. Wagner nahm nun an, dass dies zunachst nur
einzelne Individuen sein konnen, und dass nicht bloss sie, sondern
noch eine grosse Anzahl anderer leben bleiben. so dass nicht allein
die Moglichkeit, sondern auch die hohe Wahrscheinlichkeit gegeben
ist, dass die den neuen Lebensbeeinflussungen am _ besten ent-
sprechenden, von den ubrigen Individuen der betreffenden Organis-
menart abweichenden Vertreter der letzteren sich mit denjenigen
geschlechtlich mischen, die nicht in zweckentsprechender Weise
abgeandert sind. wodurch die neuen Errungenschaften wieder
verloren gehen sollten. Wagner suchte also den Nachweis zu
fiihren, dass die Darwinische Selektionstheorie nicht geeignet sei,
eine Ziichtung neuer Tier- und Pflanzenarten ohne eine Hiilfslehre,
die er in seiner ‘Migrationstheorie’ gefunden zu haben glaubte,
nachzuweisen. Er meinte, dass die vorteilhaft abgeanderten
Individuen, wenn nicht in allen, so doch in manchen Fallen auswan-
dern wtirden in eine Gegend, wo die Art, der sie angehoren, nicht
vertreten, wo also die Moglichkeit einer Kreuzung mit unabgean-
derten Individuen ausgeschlossen ist. Spater hat Wagner seine
Migrationstheorie durch die der Separation oder der raumlichen
Sonderung ersetzt, indem er zugleich die Verquickung seiner
Anschauungen mit denen des Darwinismus zurticknahm. Nach
Wagners Separationstheorie bilden sich neue Arten dadurch, dass
auf die eine oder andere Weise etliche Individuen einer Art in ein

OTHER THEORIES OF SPECIES-FORMING. 255

Gebiet gelangen, das vorher nicht von dieser Art bewohnt war.
Die Entstehung neuer Arten erklart sich dann nach Wagner
dadurch, dass, da die Individuen einer Art ja alle mehr oder
minder voneinander abweichen, die wenigen Grtinder der neuen
Art ihre Besonderheiten bewahren und nicht durch Kreuzung mit
anderen Individuen wieder einbussen wtrden. Die Anpassung
lasst Wagner aber im Sinne Lamarcks zustande kommen, und:
neben Einrichtungen, die den Organismen von Nutzen_ sind,.
erkennt er andere an, die lediglich der Ausdruck eigenttmlicher
Struktur sind. Die klimatischen Verhaltnisse sind nach Wagner
von sehr untergeordneter, die Verhinderung der Kreuzung ist
von ausschlaggebender Bedeutung. Wagner huldigte ferner der
Anschauung, dass die weisse Farbe der Polar- und die gelbe der
Wiistentiere dadurch zustande gekommen ist, dass entsprechend
gefarbte Individuen von Arten, die andere Gegenden bewohnten,.
nach den Polarlandern und den Wiisten auswanderten.”

‘Jordan, D. S., “The Origin of Species through Isolation,”
Scrence, N.>., Vol. XXII,: pp. 545-562. 19005.

* An excellent example of the careful study of the relation of a
group of recognised varieties, or sub-species of a species, to the

Grinnell’s study “limatic differences of their various geographic
of geographic ranges, is presented by Jos. Grinnell in ‘The Origin
differences in the and Distribution of the Chestnut-backed Chickadee,”
chickadee. Auk, Vol. II, pp. 364-382, 1904. I quote from this
paper the following:

“The chestnut-backed chickadee (Parus rufescens) is a boreal
species of peculiarly limited distribution. It is almost exclusively
confined to the humid Pacific Coast region of North America,
within which it is the most abundant, and in many places the
only member of the genus Parus present. We find it characteris-
tically at home within the densest coniferous forests, or along their
edges, where there is much shade and an even temperature.

“The range of the chestnut-backed chickadee is nearly two
thousand miles long, north and south, extending from a little north
of Sitka, Alaska, to some forty miles below Monterey, California.
But its width is very narrow, only within the confines of Oregon
and Washington exceeding one hundred miles, and elsewhere
usually much less, save for one or two isolated interior colonies
to be mentioned later.

“The influences determining this queer-shaped distribution area
may be safely assumed to be atmospheric humidity, with associated
floral conditions. For this habitat coincides quite accurately with
the narrow coastal belt of excessive cloudy weather and rainfall.

“The specific character distinguishing Parus rufescens from all

256 DARWINISM TO-DAY.

other American chickadees is the colour of the back, which is an
intense rusty-brown, approaching chestnut. It is of common note
that the most evident effects of similar climatic conditions on other
animals is a corresponding intensification of browns, especially
dorsally. We may, therefore, consider the chestnut-backed chicka-
dee, as indicated by its chief specific character, to be a product
exclusively of the peculiar isohumic area to which we find it
confined.

“Parus rufescens, from Sitka to Monterey, has a chestnut-coloured
back. And from Sitka to Point Arena, between which we find
the extremest humidity, another conspicuous character is uniform,—
the colour of the sides, which are also deep rusty brown. But from
Point Arena south to San Francisco Bay (Marin District), these
lateral-brown areas suddenly weaken to pale-rusty; while from
San Francisco south past Monterey (Santa Cruz District), adult
birds have the sides pure smoke-gray without a trace of rusty.

“The species thus presents geographic variation within itself, and
three distinguishable forms have been named, respectively, the chest-
nut-sided chickadee (Parus rufescens rufescens), the Marin chick-
adee (Parus rufescens neglectus), and the Santa Cruz chickadee
(Parus rufescens barlowi). But all three sub-species are unmis-
takably the chestnut-backed chickadee (Parus rufescens)....

‘““As has already been asserted, Parus rufescens doubtless arose
as a geographical race of Parus pre-hudsonicus [the hypothetical
common ancestor of the present species, Parus hudsonicus, occupy-
ing the interior of Alaska and British Columbia east to Labrador
and Nova Scotia, and Parus rufescens]. It is now called a ‘species’
because intermediates have dropped out; in other words, the
divarication is now wholly complete and there are two separate
twigs. The area of intermediate faunal conditions between the
humid coast belt and the arid interior region of British Columbia
and Alaska is very narrow, consisting, in places personally
traversed by me, of but a few miles over a mountain ridge. This
very narrowness of the area of faunal mergence probably accounts
for the lack of intermediates at the present day between hudsonicus
and rufescens.

“In the case of Parus rufescens and Parus hudsonicus, there
seems to be now a narrow hiatus between the two. At least I can
find no record of the two species having been found in the same
locality. The narrowness of the region of intermediate faunal
conditions may therefore be considered as the reason why we do
not find connecting links between hudsonicus and rufescens at the
present time. For the amount of difference between these two
chickadees does not strike me as any greater than, for instance,

OTHER THEORIES OF SPECIES-FORMING. 257

between Melospiza cinerea montana and Melospiza cinerea rufina,
between which there is continuous distribution and free interoscula-
tion. But we cannot expect any two species of birds or other
animals to present the same degrees of differentiation in the same
length of time or under the same conditions, much less under
different conditions. For in no two animals is the physical organ-
isation, in all respects, exactly the same.

“In a given aggregation of individuals constituting a new colony,
a certain amount of time is necessary for the set of environmental
factors to become operative in bringing about new _ inheritable
characters to a degree perceptible to us. Then the inherited effects
of invasion and cross-breeding from season to season from the
adjacent parent centre of differentiation will be evidenced less and
less, as time elapses, as the distance from this centre increases.
The offspring of successively further removed unions will, of course,
inherit to a less and less degree the distinctive characters of the
ancestral stock on one side and more and more of the incipient
ones on the other.

“If, now, the distance is great enough to permit of the time
required for adaptive manifestations to become innate, then we
would find new characters making their appearance distally nearest
the new centre of differentiation. If the distance were too short
we would not find new characters showing themselves because
they would be constantly crowded down by the influx of the old.
The time factor may, therefore, be reduced by the intervention of
an impassable barrier. As an instance, we find three (and there
are probably two other) insular forms of the song sparrow within
a limited distance among the Santa Barbara Islands, while through
the same distance on the adjacent mainland there is but one. Or,
in the case of continuous distribution, the time element may be
comparatively lessened by the great distance between the range
limits, and it may be still further decreased as these limits lie in
faunal areas of more emphatically different nature. The horned
larks, as well as song sparrows, furnish us several good examples
of the latter two rules.

“It is isolation, either by barriers or by sufficient distance to
more than counterbalance inheritance from the opposite type, that
seems to me to be the absolutely essential condition for the differ-
entiation of two species, at least in birds.

“A strong argument in support of this conviction is that we
never find two ‘sub-species’ breeding in the same faunal area, and
no two closely similar species, except as can be plainly accounted
for by the invasion of one of them from a separate centre of
differentiation in an adjacent faunal area. An appropriate instance

258 DARWINISM TO-DAY.

in illustration of the latter is the occurrence together, in the Siski-
you Mountains of northern California, of the brown Parus rufescens
of the wet coastal fauna and the gray Parus gambeli of the arid
Sierran fauna. (See Anderson and Grinnell, Proc. Ac. Nat. Sc.,
Phila., 1903, p. 13.) The Siskiyou Mountains occupy a line of
mergence between the two faune, and the two respectively repre-
sentative chickadees have evidently extended their ranges toward
each other until now over this one small area they occupy com-
mon ground. Several parallel cases could be cited; their signifi-
cance seems obvious.

“We come now to consider the origin of the races of Parus
rufescens. In a species of recent arrival into a new region (by
invasion from a neighbouring faunal area), as it adapts itself better
and better to its new surroundings, granted the absence of closely-
related or sharply-competing forms, its numbers will rapidly
increase. This means that there will be increased competition within
the species itself, on account of limited food supply. The alterna-
tive results are either starvation for less vigorous individuals
during recurring seasons of unusual food scarcity, or dissemination
over a large area. In a way the first might be considered as bene-
ficial in the long run, as doubtless leading to the elimination of
the weaker; such a process evidently does take place to a greater
or less degree all the time. and is important for the betterment of
the race. But as a matter of observation Nature first resorts to
all sorts of devices to ensure the spreading of individuals over all
inhabitable regions; in other words, the extremest intra-competi-
tion does not ensue until after further dissemination is impossible.
In birds we find a trait evidently developed on purpose to bring
about scattering of individuals. This is the autumnal ‘mad im-
pulse’ which occurs just after the complete annual moult, when
both birds-of-the-year and adults are in the best physical condition,
and just before the stress of winter food shortage. Even in the
most sedentary of birds, in which no other trace of a migratory
instinct is discernible, this fall season of unrest is plainly in evi-
dence. I may suggest, not unreasonably, that autumnal migration
may have had its origin in such a trait as this, the return move-
ment in the spring becoming a necessary sequence. (See Loomis,
Proc. Cal. Acad. Sc., 3d series, Zodlogy, II, Dec., 1900, 352.) It
is a matter of abundant observation that autumn is the season when
we find the most unlooked-for stragglers far out of their normal
range and when sober, stay-at-home birds, like Pipilo crissalis and
the chickadees, wander far from the native haunts where they so
closely confine themselves the rest of the year. It is also the expe-
rience of collectors that the greatest number of these stragglers

OTHER THEORIES OF SPECIES-FORMING. 25y

are birds-of-the-year, which thus, obeying the ‘mad impulse,’ are
’ led away from their birthplace into new country, where they may
take up their permanent abode, and be less likely to compete with
their parents or others of their kind. Then, too, cross-breeding
of distinctly related individuals is more likely. The records of
the Santa Cruz chickadee outside of its regular breeding range, are
all of August to October dates (Haywards, Gilroy, San José, etc.).

“Thus, as above indicated, by the occupancy of new territory
the number of individuals which can be supported will corre-
spondingly grow. Hence a vigorous colony will spread out along
lines of least resistance, being hindered by slight faunal changes,
but completely checked only by topographic or abrupt climatic
barriers. Parus hudsonicus and its near relative Parus rufescens
are boreal species, the former inhabiting the Hudsonian Zone and
the latter a certain portion of the Canadian. It seems reasonable
to suppose that rufescens differentiated in the northern part of the
humid coast belt, which has been called the Sitkan District. This
is a faunal subdivision of the Canadian Zone, and its northern
part approximates more closely Hudsonian conditions than south-
erly. Granting that the early centre of differentiation and distri-
bution of Parus pre-hudsonicus rufescens was in the northern part
of the Sitkan District, then the route of emigration would be con-
fined to the narrow southward extension of that faunal area. The
habitat of Parus rufescens thus gradually acquired the long north
and south linear appearance, as shown at this day. But when the
pioneer invaders at the south reached the vicinity of Point Arena,
they met with somewhat changed temperature and consequent’
floral conditions, but not so abrupt as to constitute a permanent
barrier. Doubtless the progress of invasion was retarded until
adaptive modifications evolved, which correlatively allowed of
further invasion, until the abrupt limits of the Santa Cruz Dis-
trict were reached.

“San Francisco Bay and the Golden Gate seem to now form a
pretty effectual barrier between neglectus on the north and barlowt
on the south. At least, among the large number of skins examined
by me with this point in view, I can find none from one side that
can be confidently determined as being identical with the race on
the other. Neither chickadee has been found east of the bay, nor
anywhere nearly so far from the coast belt, except for one record
of a specimen taken in the fall at Haywards. This has been reéx-
‘amined and proved to be barlowi, as was to be expected from its
contiguity. However, the Golden Gate is so narrow that an occa-
sional crossing may take place. This was more probable formerly,
when the redwood timber grew up to the Gate on both sides.

260 DARWINISM TO-DAY.

Heermann, in 1853, recorded the species from ‘San Francisco.’ But
now, I think, the bird is unknown for several miles on either side
of the Gate. Doubtless this barrier accounts in part for the
origin of the distinct form barlowi within so short a distance. ...

“As has become a generally accepted idea, the young plumages of
birds, if different at all from those of the adults, present a gener-
alised type of coloration; or, to express it in another way, the
young more nearly resemble recent ancestral conditions. The
familiar examples of the spotted, thrush-like plumage of the young
robin and the streaked, sparrow-like plumage of young towhees
and juncos are cases in point. Accepting this phylogenetic signifi-
cance of ontogeny, we find the chickadees giving some interesting
illustrations.

“Although the adult of barlow: has the sides pure smoke-gray,
the juvenal plumage possesses pale-rusty sides. This points
towards a rusty-sided ancestor like neglectus. This also agrees
perfectly with the distributional evidence of origin. The adult of
neglectus has pale-rusty sides; the young also has rusty sides, but
somewhat darker than in the corresponding age of barlow:, and
moreover is more nearly like the juvenal plumage of rufescens.
But the sides in adult rufescens are deep brown, almost chestnut,
while the young has much paler, merely dark-rusty sides. And
what is most significant is that the young of rufescens and hud-
sontcus are much nearer alike than are the adults, the former hav-
ing only very slightly darker rusty on the flanks. The young of
hudsonicus in respect to intensity of browns almost exactly equal
the adults of the same species, showing that the present coloration
is of very long standing, and offering further evidence that hudson-
icus is nearest the common stock form of all the chickadees under
consideration. Juvenal characters, resembling ancestral conditions,
lag behind the newer acquired adult characters.

“To repeat: The young of barlowi has the sides paler rusty than
neglectus, neglectus slightly paler than rufescens, but rufescens has
the sides slightly more rusty than hudsonicus, a sequence which
accords well with the present theories of origin.”

° Kellogg, V. L., ““New Mallophaga, I,’’ Contrib. to Biol. from the
Hopkins Seaside Laboratory of Leland Stanford Jr. University,
1896.

*° Smith, Jas. P., “Studies for Students: Geological Study of
Migration of Marine Invertebrates,” Journal of Geology, Vol. III,
Pp. 481-495, 1895.

** Any selective breeding or segregation produced by other means
than the separation of groups of individuals by actual topographic,
or geographic barriers may be called biologic or sexual isolation.

OTHER THEORIES OF SPECIES-FORMING. 261

72 Plate, L., “Uber die Bedeutung des Darwin’schen Selections-
prinzip,” p. 193, 1903.
** Hutton, F. W., “The Place of Isolation in Or-

Further refer- ganic Evolution,” Nat. Science, Vol. XI, pp. 240-246,

ences to discus- g
sions of isolation, 1°97: : ; .
** The not uncommon mating, in zoological gardens,

of lions and tigers, with the production of healthy cubs, is a case
in point.

** This principle, strongly advocated by Romanes, seems first to
have been presented by Eimer in connection with his theory of
orthogenetic evolution. At least it enters into the make-up of the
Eimerian theory. See account of Eimer’s theory in chapter x of this
book.

** Jordan, Karl, “Mechanische Selection,” 1896; see also Peter-
sen, Wilh., “Entstehung der Arten durch Physiologische Isolirung,”
Biol. Centralbl., Vol. XXII, pp. 468 ff., 1902; also Vol. XXIV, pp.
423-431, 467-473, 1904. Author describes cases of marked differ-
ence in reproductive organs (includes primary and accessory parts)
of closely allied species of Lepidoptera.

*T Snodgrass, R. E., ‘The Terminal Abdominal Segments of
Female lipulids, Jour. N.Y. Ent..Soc., Vol. X1, pp.-177-183, 1003:
“The Hypopygium of the Tipulide,” Trans. Amer. Ent. Soc., Vol.
XXX, pp. 179-235, 1904; ‘““The Hypopygium of the Dolichopodide,”’
Proce. Cal. Acad. Sci., Ser. 3, Zool, Vol. Til, pp.273-285; 1004.

*® Seebohm, H., ‘‘Physiological Selection,” 1886.

*° Wallace, A. R., “Darwinism,” p. 180, 1891.

*° Jordan, Karl, ‘““Novitates Zoologice,” pp. 426 ff., 1896.

** Vernon, H. N., “Reproductive Divergence: An Additional
Factor in Evolution,” Natural Science, Vol. XI, pp. 181-189, 1897.

** Jordan, Karl, ‘“‘Reproductive Divergence: A Factor in Evolu-
tion?” Natural Science, Vol. II, pp. 317-320, 1897.

** Pearson, Karl, “Reproductive Selection,” Natural Science, Vol.
VIII, pp. 321-325, 1806.

** Romanes, G. J., ‘Isolation in Organic Evolution,” Monist, Vol.
VIII, pp. 19-38, 1807.

*’ Gulick, J. T., “Divergent Evolution through Cumulative Segre-
gation,” Jour. Linn. Soc., Zool., Vol. XX, pp. 189-274, 1888.

*° Gulick, J. T., Jour. Linn. Soc., Zool., Vol. XX, pp. 202-211,
1888.

*7 Gulick, J. T., “Evolution, Racial and Habitudinal,” Pub. No.
25, Carnegie Institution of Washington, 1905. In this large paper
are to be found references to all of the author’s important papers.
Some of these papers are reprinted (some completely, some in
part) in this monograph.

CHAPTER X;

OTHER THEORIES OF SPECIES-FORMING AND
DESCENT (CONTINUED): THEORIES ALTER-
NALIVE TO SELECTION.

WE come now to the brief consideration of three general
theories, or groups of theories, which are offered more as
alternative or substitutionary theories for natural selection
than as auxiliary or supporting theories. These groups of
theories are the Lamarckian one, based on the inheritance
of characters acquired individually (ontogenetically) during
the lifetime of the organism due to the effects of use and
disuse and functional stimuli; the general conception of
orthogenesis variously provided for by Nagel, Eimer,
Jaeckel (metakinesis), and others, and finally the theory of
heterogenesis, suggested by von Kolliker, definitely formu-
lated by Korschinsky, and most recently, and importantly,
developed by de Vries. Few biologists would hold any of
these theories to be exclusively alternative with natural
selection; de Vries himself would restrict natural selection
but little in its large and effective control or determination
of the general course of descent. But all of these theories
offer distinctly substitutional methods of species-forming,
and one of them includes certainly the most favoured expla-
nation, next to selection, of adaptation, while the authors or
later up-holders of some of them actually deny any con-
structive, that is, adaptational, species-forming or descent-
controlling, influence of natural selection.

The Lamarckian Theory.—It is a great presumption to
attempt to offer in so small a book as this any exposition of
a theory so long known and elaborately developed as the ex-

262

OTHER THEORIES OF SPECIES-FORMING. 263

planation of adaptation and species-forming known as La-
marckism. Lamarck* proposed his theory at
a time most inopportune; it met with no gen-
eral acceptance, but in later years, post-Darwinian years,
fair-minded biologists have turned back to the books and
papers of this pioneer French exponent of the evolution
principle and have given his theory the careful attention and
scrutiny it deserves—but which it failed to get from
Lamarck’s contemporaries. This reéxamination of the La-
marckian theory or theories has given rise to most radically —
divergent opinion and belief concerning its worth: many .
biologists account it of great value, others reject it prac-
tically in toto. But this acceptance or rejection depends
almost entirely on one’s attitude toward a single funda-
mental part of it, namely, the assumption that variations,
modifications, or characteristics acquired during the life-
time of an individual, these modifications usually being due
to use, disuse, or other functional stimulation of organs and
parts, can be transmitted by this individual to its offspring.
If such newly-acquired, non-inherited characteristics can be
transmitted in full and in detail, or even approximately so,
from the parent to the young, then Lamarckism obviously
offers the simplest of all the explanations so far presented,
of nearly all active and of many passive adaptations. If
such characters cannot be so transmitted, then Lamarckism,
as plausible, as reasonable, as simple and effective as it
seems to be, is practically without validity.

Now this matter of the inheritance of acquired charac-
ters, apparently easily susceptible of definite proof or refuta-

The fehectianse ON by observation and experiment, has been
of acquired char- for years and is to-day one of the burning prob-
one lems of biology. There is no general agree-
ment about it, no consensus of authority even. Just at pres-
ent the weight of evidence inclines strongly against such
an inheritance, chiefly because of Weismann’s successfully

Lamarckism.

264 DARWINISM TO-DAY.

destructive criticism of about all the evidence of observa-
tion which has been offered in behalf of it. And yet just at
the present time do biologists recognise more keenly than ever
the need and relief the actuality of such inheritance would
give them in their attempts to solve the great problems of
adaptation and species-forming? I cannot undertake to say
whether more reputable biologists disbelieve in than believe
in the existence of such inheritance, but it is obvious that
the disbelievers have the present prestige of apparent vic-
tory: they call for convincing evidence of such inheritance,
and it is not produced. On the other hand, there are many
reputable, thoughtful, honest, actively working biologists and
paleontologists (particularly many paleontologists in pro-
portion to the total number of palzontological students) who
say, although not loudly and even a bit shamefacedly, per-
haps, that they must believe in the possibility and the actu-
ality of this inheritance; there is no getting forward with-
out it.

In taking up our brief exposition of Lamarckism, let me
say first that only in post-Darwinian years has Lamarckism
been put so strongly in contrast with Darwinism as it has.
Darwin himself included part of Lamarckism as a minor
factor or influence in his explanation of adaptation and
species-forming, and Plate, in the recent most notable criti-
cal discussion of Darwinism, takes nearly exactly the old
ground of Darwin, namely, an acceptance of the inheritance,
in some degree and under some conditions, of acquired
characters, and the consequent possibility of a certain
amount of Lamarckian orthogenesis, 1. e., an orthogenesis
due to the inheritance of the results of use, disuse, and func-
tional stimuli. It is only neo-Darwinism (of Weismann,
Wallace, and others) and neo-Lamarckism (of Spencer,
Packard, and others) that are so radically opposed, so mutu-
ally exclusive.

That an animal in its lifetime, and especially during its

OTHER THEORIES OF SPECIES-FORMING, 265

immature life can effect very considerable changes in some

The concep- Of its body-parts by special use or disuse of
worl haleeaian these parts, or that certain parts may be modi-
Lamarok. fied through the influence of external stimuli, is
familiar knowledge. Let one recall the increase of the
blacksmith’s biceps and inversely the degeneration of un-
used muscles, and the thickening or callousing of palms or
other parts of the skin exposed to repeated rough contact.
Bones have ridges developed on them by repeated muscle-
pulls, the hands and eyes can be trained to special functional
skill which involves important although perhaps slight physi-.
cal changes, the heart and lungs can be enlarged by special
use; in short, almost any of the organs of the body, which
are actively used, can be modified either by unusual or extra
use, or by unusual lack of use. Now this use is, in Nature,
almost always of the character of a better aiding in success-
ful living; that is, it is adaptive use. Animals often chased
by enemies become fleeter by practice; animals that must

_ dig for roots or climb trees for leaves and fruits, or dive for

fishes, or leap over obstacles, come by repeated digging, climb-
ing, diving, or leaping to do these things better ; the muscles
and tendons and bones work together better and better,
become physically modified in accordance with these endeav-
ours. If such betterment of organs and their functions
acquired by individuals could be inherited by their young,
it 1s obvious that general adaptations of this sort could be
rapidly developed in the course of generations, and new
species, new, that is, because of the adaptive changes thus
effected, be formed. This is the essential thought in
Lamarck’s theory of the method of adaptation and species-
forming. In almost all criticisms of Lamarckism one reads
much contemptuous reference to the expected results of the
organism’s “willing” to vary or change in this or that direc-
tion. As a matter of fact the critics of Lamarckism give
that rather absurd feature of alleged Lamarckism much

266 DARWINISM TO-DAY.

more conspicuousness than Lamarck did. He did, indeed,
make some reference to the possible volitional effort of the
organism to change along certain desirable lines, but it is
evident that Lamarck had more in mind the animal’s desires
and needs to stretch up higher for leaves or to dig better or
run faster, leading to actual attempts to do these things, than
to any expected results of mere mental wishing or willing.
The essential principle of Lamarckism is an orthogenetic
evolutionary progress toward better and finer adaptation and
adjustment resulting from the inherited effects of actual use,
disuse, and functional stimulation of parts. It is a great
thought and a clear one, and only needs the proof of the
actuality of the inheritance of individually acquired char-
acters to make it one of the principal causal explanations
of adaptation and species change.

However, it is exactly this proof that is wanting. At any
rate, proof of the character and extent necessary to con-

iui all or even a majority of biologists is
successful attack Wanting. The examples or cases brought for-
on Lamarckism. ard by Lamarckians of the alleged inheritance
of mutilations, of the results of disease, and of use and
disuse, are not convincing. It is one of Weismann’s posi-
tive contributions to biology to have analysed case after
case of alleged inheritance of acquired characters, and shown
its falseness or at least uncertainty. Many of these cases
he has been able to explain as a result of selection; others
remain inexplicable; a few,” only, are insisted on by the
Lamarckian champions as indisputable examples of such
inheritance. But this very paucity of so-called proved
cases, where there should be thousands of obvious ex-
amples if the principle were really sound, is argument against
Lamarckism.

Our knowledge, too, of the mechanism of heredity makes
strongly against the theory of the inheritance of acquired
characters. Another of Weismann’s positive contributions

es i ahy ee bell.
BCE Siting? ;

OTHER THEORIES OF SPECIES-FORMING. 267

to biology is his generally sound distinction between the
germ-plasm and the soma-plasm and parts of the many-
celled body. At maturity the animal body is composed of a
small mass of germ-plasm (germ-cells) situated in the
ovaries or testes, and a great mass of somatic tissues and
organs, all the rest of the body, in fact. Now what is the
condition that exists in the body after a somatic part is
modified by use or disuse or by other functional stimulus, as
when a muscle is enlarged by exercise, the sole of the foot
calloused by going barefoot, an ear more finely attuned by
training? We have a definite physical change in a definite
organ, but is the germ-plasm in any way changed or
affected by this superficial or specific somatic modification,
or if changed is it changed so that it will reproduce in its
future development a similar change in the same organ of
the future new individual? What possible mechanism have
we in the body to produce or insure such an effect on the
germ-plasm? The answer is obvious and flat; we certainly
know of no such mechanism; in fact what we do know of
the relation of the germ-cells to the rest of the body makes
any satisfactory conception of such a mechanism as yet
impossible.

Not that certain external conditions may not directly
affect the germ-cells, imbedded and concealed as they are

Reh (alist in the body. me arying conditions of tempera-
the way of ture,* of humidity, and of magnetism, perhaps,
ee, certainly anything influencing the food supply
acquiredchar- and nutrition, can influence the germ-cells at
a the same time as it affects all the rest of the
body. But will this influence photograph on these un-
differentiated cells the same picture that it impresses on the

* While temperature may be looked on as an extrinsic influence
affecting germ-cells as well as all other parts of the body, it must be
kept in mind that warm-blooded animals (birds and mammals)

regulate the inner temperature of the body. So changes in external
temperature would but slightly, or not at all, affect the germ-cells.

268 DARWINISM TO-DAY.

affected somatic parts. A high temperature or a moist at-
mosphere may modify the colour of the skin, change the pat-
tern of the body superficies, but will overheated germ-cells
produce new individuals showing the same changes of skin
colour and pattern if the same conditions of environment of
the soma are not repeated? How much less conceivable,
then, is the influencing of the germ-cells so as to compel
them to reproduce on daughter body-parts specific effects
produced on special parental body-parts by such specific and
localised influences as vigorous use of an arm, disuse of a
leg muscle, repeated contact of the palm of the hand with
hard bodies. Indeed, this lack of means of relating the
germ-plasm to the soma, the rest of the body, has stood
much in the way of any satisfactory conception of the phe-
nomena of heredity, that is, the reproduction by the germ-
cells of new individuals resembling the parental, and kas
led to constant and thoughtful attention and speculation ever
since the time of Darwin; indeed, from long before Dar-
win’s time.

One of the most favoured ways of attempting to explain
how the germ-cells can represent in their make-up, and
possess the capacity to develop into, the whole complex body,
has been to conceive of the giving off of small representa-
tive particles from all the cells of the body which should be
carried by the blood to the germ-plasm and deposited in the
germ-cells. The germ-cells in their development would
then, by virtue of this manifold representation, be able to
expand into the whole body during a shorter or longer
course of development and growth. This notion of the com-
position of the germ-plasm of micromeres collected from all
the somatic cells, is the conception at the basis of Buffon’s
theory of “organic molecules,’ of Spencer’s “physiological
units,” Maggi’s “plastidules,’ Altmann’s ‘‘bioblasts,” Wies-
ner’s ‘“‘plasomes,” Darwin’s ‘“gemmules,” Galton’s “stirps,”
Nageli’s “micelle,’ Weismann’s “biophors and determi-

OTHER THEORIES OF SPECIES-FORMING. 269

nants,’ and of numerous other micromeric theories.* But
the facts of budding, especially as exemplified in plants,
and of regeneration among animals, both of these kinds of
phenomena seeming to show that germ-plasm is not neces-
sarily limited to the germ-cells, strictly so-called, have pre-
vented the acceptance of a too rigorous interpretation of
Weismann’s distinction between the germ-plasm and the
soma, and have led to some theories of germ-plasm make-up
and disposition differing from the ones proposing a rigid
restriction of germ-plasm to thé germ-cells. The facts that
in many plants any part, as a bit of a twig, say, if cut off, can
reproduce the whole plant just as effectively as a seed
(germ-cell) can, and that many animals can reproduce con-
siderable and complex parts, if lost by accident or self-
mutilation, show that there often resides in somatic cells of
much specialisation the capacity to reproduce not only cells
of their own kind but others of much variety and different
specialisation. So some biologists believe that there is either
a net-work of primitive germ-plasm extending throughout
the soma cells (Nageli’s idioplasm theory for example), or
that each somatic cell (at least those with the capacity of
regeneration or reproduction by budding, cuttings, etc.) con-
tains a little primitive germ-plasm stuff besides its own
soma-plasm. And some authors have seen in such theories
of a widely diffused germ-plasm a mechanism for the trans-
mission from the soma to the central germ-cells of the
effects of use, disuse, and functional stimuli derived from
external sources. But does even this conception of a diffuse
and connected germ-plasm, after all, clear up in any way
our difficulty? It makes it easier to see how germ-plasm
may be affected by external and superficial influences, but
does it explain in any degree how these effects can be car-
ried to the germ-cells and so stamped on them as to compel
them to reproduce photographically in their later develop-
ment into new individuals, the specific effects that use, dis-

270 DARWINISM TO-DAY.

use, and external stimuli may have had on specific soma
parts of the parent?

Indeed, Haacke * well points out that many or most cases
of apparently direct working of extrinsic influences on the
body are really indirect, in that these influences
do not actually directly modify the structure, as
a blacksmith’s hammer modifies the shape of a
piece of red-hot iron, or a seal shapes the drop of melted
wax, but that they do it indirectly as stimuli inducing chemi-
cal processes, nervous impulses, etc. The adaptive re-
arrangement of spongy tissue in broken and poorly reset
long bones, apparently a direct reaction, is really only in-
direct, occurring through complex chemical processes, 1. é.,
the bringing of special bone-forming materials to certain
places, etc. The outer influences are all stimuli, not actual
sufficient causes or manipulations.

Haacke makes a proposal of much ingenuity, after a keen
and suggestive discussion of the inheritance of acquired
characters problem, to explain how such an inheritance may
be effected. It is based on the fact that no characters are
directly acquired; that is, that any change is only the result
of some external stimulus and not of a directly and imme-
diately moulding cause, and that, therefore, in any phenom-
enon of stimulus and effect much more of the body substance
than that composing the exact part or region modified is
influenced. From this Haacke sees the possibility, even the
necessity, of a modification of the whole constitution, includ-
ing the germ-plasm (or perhaps the germ-plasm is modified
as a result of the modification of the whole constitution or
body in which the germ-plasm is being developed and
formed). Thus every acquirement of a new character or
change in an old one must or may affect the germ-plasm.
With regard to passive organs such as the chitin skeletal
parts of insects and crabs, Haacke points out that they are
only the product of active organs, 1. e., the secreting skin-

Haacke’s
discussion,

OTHER THEORIES OF SPECIES-FORMING. 271

cells, etc. Use and disuse are equivalent simply to much or
little metabolism, and metabolism is as necessary to produce
passive organs or to change them, as use is to make muscles
larger.

However, despite the successful destructive criticism by
Weismann and the neo-Darwinians of the alleged cases of

Maty natu UC inheritance of acquired characters adduced
ists believe in. by the Lamarckians, and in spite of our lack of
the inheritance A Ake :
of acquired knowledge, and indeed, difficulty of conception
ohatactert: of any mechanism in the body capable of im-
pressing on the germ-plasm the effects of use, disuse, and
external stimuli in such a way as to compel a photographic
reproduction in the young of these effects as manifest in
the soma of the parent, numerous biologists do not hesitate
to avow their conviction of the actuality of such inheritance.
Now these biologists must have some basis of observation or
scientific fact for their belief. What is this basis? They rest
their belief largely upon a kind of proof by indirection, a
certain necessity of consequence of other facts, and a logical
argument by elimination. The actual observed status of
animal life to-day and, as revealed by fossils, in past ages,
which is that of the existence of certain lines of descent or
evolution obviously following lines of modification based
on use and disuse; the inadequacy of natural selection to
explain the cumulation of adaptive modification until such
modification shall have reached a life-and-death determin-
ing selective value; the apparent impossibility of explaining
the continued degeneration of vestigial organs by natural
selection; the great difficulty of explaining correlative or
coadaptive modifications by selection alone; the possibility
that our lack of knowledge of a mechanism for ensuring the
hereditary transmission of acquired characters may be over-
come with further knowledge of the ultimate structure and
capacity of the germ-plasm; the great reasonableness and
logical plausibility of the whole Lamarckian conception;

272 DARWINISM TO-DAY.

these and other similarly not wholly convincing reasons are
the sort of not very admirable scientific evidence that the
believers in Lamarckism have to stand on. Two groups of
scientific men are especially well represented among the
Lamarckians: namely, paleontologists and pathologists.
(Not all palzontologists and pathologists believe in the
inheritance of acquired characters.) Both of these groups
are familiar with facts that are unfamiliar to biologists gen-
erally. And to my mind it is important that biologists should
recognise the fact that familiarity with the facts of histor-
ical geology on the one hand and with teratogenesis and
human disease on the other, seems to lead to a belief in
Lamarckism.* It should lead the general biologist to be
less positive in his sureness of the invalidity of Lamarckism.

But even were the inheritance of acquired characters now
an established fact, or if it should come to be one, it must

Lamarckism be kept in mind that Lamarckism could be sub-

unable toex-— ctituted only partly for Darwinism. There are
plain all adapta- ene ; :
tions. many adaptations and much species-forming

that Lamarckism might explain, but also there are hosts of
adaptations that Lamarckism cannot explain. Plate,’ who
defends natural selection but accepts some part of Lamarck-
ism, has pointed this out clearly. He asks how the so-called
“passive adaptations” could be explained by Lamarckism.
“The salivary glands of a non-poisonous snake could pro-
duce ever so much saliva, but it would not become poison-
ous by this, just as little as simple teeth could change by
use to grooved teeth and these to tubular ones. The tusks
of Babiriussa could not be led to grow through the skin of
the cheeks through use, for they would have to be actually

* A scientific man representing another phase of biologic activity,
and a man who has enjoyed an extraordinary opportunity for the
observation and testing of modes of inheritance, also believes
strongly in Lamarckism. This is Luther Burbank, the famous Cali-

fornia plant-breeder. For some account ° of the scientific aspects of
Burbank’s work, see the appendix of this chapter.

OTHER THEORIES OF SPECIES-FORMING. 273

covered by the flesh for awhile in this process, and during
this time be incapable of use. With Fierasfer, the fish that
lives in sea-cucumbers ( Holothurians), the anus lies far for-
ward in the throat so that the fish has only to thrust its head
through the anus of the sea-cucumber in order to void its
feces. How can use of the intestine or its peristaltic move-
ment have produced such a remarkable change in position
of the anus?” Plate‘ offers other similar examples of adap-
tations inexplicable by Lamarckism, and justly says that
hundreds of others could be adduced. He presents suc-
cinctly the possibilities of Lamarckism, the inheritance of
acquired characters being granted, as follows:

Lamarckism could explain

(1) many indifferent characters: example, changes of
temperature produce proportional changes in the
colour-pattern of butterflies’ wings;

{2) many simple adaptations of active organs: example,
a muscle becomes stronger through use, and creates
a crest on a bone through pulls;

(3) some simple adaptations of passive organs (so-called
direct adaptations): example, in the whales, the
water might directly affect the skin and sub-cutane-
ous tissue and thus produce the loss of hair and the
layer of fat;

Lamarckism could not explain

(1) many characters of active adaptation, even though
of simple kind: example, the penetrating of the lung-
sacs of birds through hair-fine holes into all the
bones ;

(2) many complicated adaptations of active organs: ex-
amples, light-making organs, eyes, smelling-organs,
auditory organs ;

(3) all complicated passive adaptations: example, mim-
icry.

Even if we are ready to admit the possibility or actuality

274 DARWINISM TO-DAY.

of the inheritance of acquired characters in some degree or
under certain conditions—and this partial acceptance has.
always seemed to me no more justified than the flat accept-
ance of the principle in its entirety; it has seemed a weak
sort of attempt at compromise with no real basis in reason
and effecting no advantage in clearing up the problem—
there can be no acceptance of the all-sufficiency of Lamarck-
ism as an explanation of adaptation, species-forming, and
descent, any more than there can be such an acceptance of
the all-sufficiency of natural selection. Adaptation and spe-
cies-forming are not, to my mind, one and the same problem:
adaptation can and does lead to species-forming, but species.
are formed that are not the results of adaptive modifica-
tion; whose specific characteristics are indifferent; that are,
in a word, non-adaptive species. De Vries’s new species of
evening primroses have a cause not associated with adapta-
tion. Now Lamarckism certainly cannot explain non-
adaptive species any better than selection can. Both selec-
tion and the inheritance of the effects of use, disuse, and
external stimuli are primarily explanations of adaptations
and of adaptive species-forming. Lamarckism is, perhaps,
through its inclusion of the perpetuation of the direct influ-
ence of external stimuli, in better condition to explain non-
adaptive species, but both of these genius-offered explana-
tions of organic evolution need the aid of another or other
factors: the unknown factors of evolution, to speak with
Osborn.

Orthogenesis—One of the principal criticisms of the
natural selection theory is that of the impossibility of ex-

cane plaining the beginnings of advantageous modi-
dence for ortho- fication and the beginnings of new organs, by
genetic evolution. +6 selection of fluctuating individual variation,
and of explaining the apparent cases of the existence of
determinate variation and the admitted cases of forthright
development along fixed lines not apparently advantageous,

OTHER THEORIES OF SPECIES-FORMING. 275

and finally of explaining the definite cases of ultra-develop-
ment of parts and species beyond the point of advantage even
to such unfavourable degrees as lead to death and extinction.
Paleontology * reveals to us the one-time existence of ani-
mals, of groups of animals, and of lines of descent, which
have had characteristics which led to extinction. The un-
wieldiness of the giant Cretaceous reptiles, the fixed habit
of life of the crinoids, the coiling of the ammonites and
nautili, the gigantic antlers of the Irish stag—all these are
examples of development along disadvantageous lines, or to
disadvantageous degrees. ace statistical studies of varia-
tion have made known numerous cases ° where the slight, as
yet non-significant (in a life-and-death struggle) variation
in pattern of insects, in dimension of parts, in relative pro-
portions of superficial non-active structures, are not for-
tuitous, that is, do not occur scattered evenly about a mean
or mode according to the law of error, but show an obvious
and consistent tendency to occur along certain lines, to
accumulate in certain directions. Many biologists see in
variation and in species-forming certain determinate char-
acteristics exhibited by, or lines or paths being followed by
all or most of the individuals of successive generations ; and
see in descent certain phenomena of forthright progressive
movement which they find selection based on utility unable
to explain. Various theories to account for this apparent
orthogenetic, but not ortho-selective, development have
therefore been proposed by biologists, most of which
theories and most of which biologists are to be looked on as
antagonistic to the selection theory. For if a theory of ortho-—
genesis is sufficient to explain those lines of variation and
development not explicable by selection, it usually seems to
its maker to be sufficient to explain other lines of evolution.

It may very likely occur to some that in speaking of ortho-
genetic development as contrasted with descent governed by
selection we are making a distinction without a difference,

276 DARWINISM TO-DAY.

in that it is obvious that selection also produces ortho-
genetic evolution, that is, evolution along definite lines;
that in fact it can produce no other kind of
Orthogenesis evolution. To attribute orthogenetic results to
contrasted with gcteeh is ; ;
orthoselection, Natural selection is quite right,and some one has
proposed the name orthoselection to distinguish
orthogenetic evolution as produced by selection from such
results produced independently, or at least partly inde-
pendently of selection, that is produced in accordance with
any one or more of the so-called theories of orthogenesis.
All this latter kind of orthogenesis is distinguished from
orthoselection in that it presumes all or most of the indi-
viduals of successive generations to be modified, to vary,
that is, in a similar manner as a result of factors, intrinsic
or extrinsic, producing determinate variation. This is
plainly different from orthoselection, in which definite lines
of development are produced by the eradication, through the
rigour of selective struggle, of all other lines. Variation
may be wholly fortuitous, miscellaneous, indeterminate; but
selection permits only certain kinds of variation to persist,
to accumulate. In true orthogenesis the variation, and
hence the lines of modification, are predetermined. It seems
obvious, however, to any believer in natural selection that
sooner or later the fate of these lines of development will
come into the hands of selection. And most orthogenesists
do indeed admit this. But it is precisely in the making of
a start in modification that orthogenesis fills a long-felt
want, and if capable of proof, should be gladly received by
Darwinians as an important auxiliary theory in the ex-
planation of modification, species-forming, and descent.
The first of these theories of orthogenesis has just been
explained, for Lamarckism may be looked on as an expla-
nation of orthogenetic evolution based on the perpetuation
and accumulation of the effects of use, disuse, and the
direct effects of functional stimuli. Roux’s battle of the

OTHER THEORIES OF SPECIES-FORMING. 277

parts theory, and Weismann’s theory of germinal selection
are also in a way theories of orthogenesis: they explain how
variations begin and continue along fixed lines, but they
both soon surrender control of descent to natural selection.
| There are, however, two or three theories of
Different types orthogenesis which have been developed by
of theories of
orthogenesis, their proposers to the degree where they are
boldly offered as substitutes for natural selec-
tion. Two especially notable theories of this character are
those proposed and defended respectively by Nageli and by
Eimer. These two are not only the most notable and most
completely elaborated of orthogenetic theories but they
represent two radically different points of view among the
orthogenesists themselves, in that Nageli found his ortho-
genesis-producing factor or cause in a_somewhat mystical
vitalistic inner force, or so-called V ervollkomnungsprinsip,
in the organism, while E imer finds orthogenesis produced
and controlled by the directly working external factors of
climate, food supply, and environment generally. Similar
conceptions or beliefs regarding the direct and accumulating
effect of environmental factors have been presented by Dar-
win, Haeckel, Cope, Henslow, Emery, Piepers, Lloyd
Morgan, and numerous others. In fact probably a majority
of biologists entertain a conviction,—often not clearly de-
fined and generally unaccompanied by any satisfactory con-
ception of a mechanism for achieving what they believe
to exist,—of the actuality of an influence on organic modifi-
cation and descent directly exerted by those various external
factors or conditions of organic life which we call, collec-
tively, environment.
Nageli’s *” theory of orthogenesis depends upon the as-
sumption of his so-called principle of progressive develop-
Nigeli's theory Ment (Vervollkomnungsprinzip), a something
of orthogenesis. inherent in the organic world which makes
each organism in itself a force or factor making towards

Pema OL

278 DARWINISM TO-DAY.

specialisation, adaptation, that is, towards progressive evo-
lution. Other authors who accept such a theory of an inher-
ent driving force in organisms speak of this factor variously
as an “inner directive force,’ an “inner law of development,”
or an “intrinsic tendency towards progress,” etc. Nageli
believes that animals and plants would have developed about
as they have even had no struggle for existence taken place
and the climatic and geologic conditions and changes been
quite different from what they actually have been. Kor-
schinsky ** says: “In order to explain the origin of higher
forms out of lower it is necessary to assume in the organism
a special tendency towards progress.”” That is, to the be-
lievers in this kind of a theory of orthogenesis organic
evolution has been and is now ruled by unknown inner
forces inherent in organisfns, and has been independent of
the influence of the outer world. The lines of evolution are
immanent, unchangeable, and ever slowly stretch toward
some ideal goal. It is needless to say that but few biologists
confess to such a belief. However much in the dark we
may be regarding the whole great secret of bionomics, how-
ever partial and fragmentary our knowledge of the processes
and mechanism of evolution, such an assumption of a mystic,
essentially teleologic force wholly independent of and
dominating all the physico-chemical forces and influences
that we do know and the reactions and behaviour of living
matter to these influences which we are beginning to
recognise and understand with some clearness and fulness—
such a surrender of all our hardly won actual scientific
knowledge in favour of an unknown, unproved, mystic vital
force we are not prepared to make. As Plate well says, such
a theory of orthogenesis ** is opposed, in sharpest contrast,
to the very spirit of science.

On the contrary, the theories of orthogenesis of the
general type exemplified by Eimer’s * are directly in line
with the spirit of modern biological methods and investiga-

OTHER THEORIES OF SPECIES-FORMING. 279

tions; they rest on the assumption that physico-chemical
factors produce direct effects on the plastic organism, and
Mcelce type that such effects, repeated and intensified, re-
of orthogenetic sult in a certain degree of modification or con-
roach trol of variation and evolution. To be sure,
there is not yet proposed a very satisfactory mechanism
for conveying the environmental influence to, and trans-
lating it into definite effect on the course of development,
but the obvious fact that environment does strongly affect
and modify individual function and structure and the rea-
sonable belief that the modification of the race must ulti-
mately rest on and proceed from the modification of the
individual, make the theories of orthogenesis based on en-
vironmental influence very suggestive and of distinct
scientific value. In addition, too, there is a certain amount
of actual evidence of observation for orthogenesis: an
evidence of two categories, namely, positive affirmative
evidence,’ and negative evidence drawn from the inade-
quacy of other theories, notably natural selection, to explain
certain observed phenomena which can be explained on the
assumption of an orthogenesis. The general character of
this evidence is indicated in our first paragraph treating of
orthogenesis. To this may be added an ab-
eae ton stract of Plate’s’® résumé of the facts or
to prove ortho- phenomena which may be looked on as positive
iil evidence for orthogenesis (although Plate cau-
tiously notes that some of these may be only phenomena of
orthoselection). These phenomena pointing toward ortho-
genesis tay be grouped into six categories:

1. The “analogous or parallel variations” which have
been recognised ever since Darwin’s time, he, himself, list-
ing many examples of them. These are varia-
tions of unmistakably similar character, which
often appear in different branches of the same
large group. “Comparative anatomy reveals many ex-

Parallelisms in
‘variation.

280 DARWINISM TO-DAY.

amples to show that a definite or determinate direction of
modification may be noted in all the sub-groups of a large
family, although appearing in unequal degree in different
species. Examples are the reduction of the hind toes among
the Artiodactyls which has continued in several genera
(giraffe, camel, llama) up to a complete disappearance, and
the modification of the originally single genital duct into a
double and finally triple one, as occurs in both the Pul-
monata and the Opisthobranchiata. Often a progressive
development can, on mechanical or physical grounds, come
about by a modification in but one direction, and may lead
thus to convergent changes, as the development of a lens in
a pigment fleck in the case of many unrelated lower animals,
the similarity of the heart in crocodiles, birds, and mammals,
the appearance of a placenta with Permales among the
Marsupials and also among the Placentalia.”

2. The numerous “excessive structures” which are de-
veloped far beyond the limits of usefulness. Examples, the
tusks of the wild boar (Babirussa alfurus) ; the
giant horns of many wild sheep and goats;
the enormously elongated thread-like neck of
several Rhynchophorous beetles, as Apoderus tenuissimus,
etc.; the absurdly long eye-stalks of such crustaceans as
Macrophthalmus laterillei and Podophthalmus vigil; Meso-
plodon, whose mouth can be opened but a little when
the animal is full grown because on each side an under
tooth grows around the upper jaw. Such “excessive
structures” have undoubtedly led to the dying out of many
former species: examples, the tusks of the mammoth, the
antlers of the Irish stag, the canines of Smuilodon neogeus.

3. “The constitution, or actual chemical composition of the
body permits, in many cases, changes only in few directions.
The animal or plant breeder may by no means produce any
wished-for form or colour. No one has yet succeeded in
producing a blue Maiblume, a grass with divided leaves, a

Over-speciali-
sations.

OTHER THEORIES OF SPECIES-FORMING. 28%

hen with a parrot’s beak. And we can declare with con-
fidence that a chorda dorsalis can never appear in a beetle.

Awan Through the very fact that an animal belongs
limitationson to a group the possibilities of variation are
agian distinctly delimited and in many special cases
these possibilities may indeed be very narrow.” Plate
does not mention in this connection the fact that some
biologists have seen in this restriction of the range of varia-
tion which inevitably accompanies specialisation in the
development of animal groups an important factor in the
determination of lines of descent. Cope gave much import-
ance to this factor, and'very recently Rosa,’* in a most in-
genious and suggestive paper, attributes to this “progressive
reduction of variability” a large importance in the dying
out of old species and the origin of new ones.

4. “By the correlations which bind each organ to others.
the range of variation is also restricted.”

5. Many facts of paleontology seem to prove the existence
of orthogenetic evolution. ‘Wherever a large supply of ma-

Factsfrom terial permits the working out of a phyletic.
Sine: series, we always see a limited number of lines
thogenesis, of development, which despite occasional side-
branching run essentially in straight lines, in steps which
lead gradually one to another.”

6. The phyletic series (chains of forms) of recent species

Single phy- also show, where we are able to trace them,
letic lines. © distinctive single lines of development.

Eimer’s particular theory of orthogenesis, which we
have chosen aS a~representative Of the orthogenetic doc-
trine in general (although few biologists who believe in
the principle of orthogenesis accept this theory in detail),
may be briefly stated as follows:

Modifications of organisms, that is, lines of evolution, are
not miscellaneous, but occur according to control along a
few definite directions, these lines of change being deter-

282 DARWINISM TO-DAY.

mined not at all, at least in their beginnings, by selection on
a basis of utility, but as the result of the inheritance of ac-
quired characters and according to the laws
of organic growth (organophysis). The prin-
cipal effects of these laws of organic growth are
made manifest by the determinant evolution, or orthogenesis,
which obtains, and which is in direct contrast to that kind of
evolution which natural selection, if it really effected any-
thing, would bring about. For evolution by natural selec-
tion would occur along all sorts of heterogeneous and radiat-
ing lines which is, according to Eimer, actually not the
case. A few definite lines obtain from which occasional
branches are given off, the whole building the familiar
phyletic or genealogical tree. That these main lines and
branches are not themselves the result of selection is proved
by the fact that much evolution and modification of organ-
isms is not directly useful, a majority, indeed, of the char-
acters distinguishing different species not being characters
of utility." Only when a character or line of evolution
becomes of a life-and-death-determining disadvantage can
selection interfere with evolution by orthogenesis. And this
interference is always and only of the nature of a stamping
out, never of the character of the creation of new characters
or lines. Eimer believes in the inheritance of acquired
characters, believes in a considerable species-forming influ-
ence of geographical isolation, that is, finds such isolation
very helpful to the general basic organic growth evolution
principle and finds the actual causes of orthogenesis “‘to
lie in the effects of external influences, climate, nutrition,
on the given constitution of the organism.” “This is not
Lamarckism,” Eimer points out, anxious to have his theory
to his own credit, ‘““for Lamarck ascribed to the external in-
fluences no effects on the animal body, and only very little
on the plant body.” Eimer adds that the effects of external
influences are usually considered a part of Lamarckism;

Eimer’s theory
of orthogenesis,

Bi v
ih

OTHER THEORIES OF SPECIES-FORMING. 283

as a matter of fact Lamarck’s species-forming influences
were, chiefly at least, the inherited results of actual use or
disuse, or of other functional stimulation initiated or exer-
cised actively by the organism itself. In the actual varia-
tion of organisms Eimer sees none of that “oscillation” or
equal variation around a median or modal point character-
istic of the Darwinian conception, but sees always a deter-
minate variation in a few definite lines. He denies positively
any capacity on the part of natural selection to create species,
finding it effective in breaking the continuous organic chain,
that is, of separating it into species, only when aided by
geographical isolation. The actual species-forming, that is,
the breaking up into specific units of the orthogenetic lines
of change instituted by his dynamic factors, he finds to de-
pend on three chief moments, viz., a_standing still or cessa-
tion _of development (Entwicklungsstillstand) : a sudden de-
velopment by leaps, called halmatogenesis (which i: is almost
exactly the fundamental idea in Korschinsky’ s and de Vries S

men, nena

culty in reproduction mee is the socal factor’ in Ro-
manes’s theory of physiological selection proposed ten years
later). It is of interest to note Eimer’s claim to the original
conception of species-forming both by heterogenesis and
through physiological selection, with which two theories
the names of de Vries and Romanes, respectively, are com-
monly associated as those of the original proposers.

Of Eimer’s three species-forming factors he lays most
stress on the one I have first mentioned viz., Entwicklungs-
stillstand. “The origin of species depends essentially on
Entwicklungsstillstand or Genepistase, that is, the standing
still of certain forms at definite stages in the developmental
line, while others go on.” This permits of the origin of
numerous different species in the same locality or region,
without any need of isolation. As orthogenesis modifies,
that is, causes to vary in the same way, many individuals at

—

284 DARWINISM TO-DAY.

a time, it is easy to see that if some of these produce young
which do not proceed farther along the orthogenetic line,
that is, do not vary farther, while others produce progeny
that tend to move on along the line or lines of determinate
variation, new species can be dropped, as it were, out of the
general course of the orthogenetic evolution all along. An
if these persist we have a series of distinct organic forms all
related chainwise although living simultaneously and in the
same region. This cessation of development can lead to
many added new forms when it occurs in the form of
Heterepistase, that is, where only a few characteristics re-
main fixed at some early developmental stage while others
goon. By the fixing or cessation of development in differ-
ent small groups of characteristics, and in different combina-
tions of these groups many new species may result. All
cases of so-called atavism are interpreted by Eimer simply
as examples of his Entwicklungsstillstand, this cessation of
development occurring in the atavistic organs at a very early
stage.

We should not omit mention, in connection with Eimer’s
theory, of a point upon which he lays great stress, and that
is that his theery is not the result of pure speculation, but is
the unavoidable conclusien arrived at by long years of
specific observations and study of the facts obtaining in the
case of the relations, conditions, and course of evolution of
certain groups of organisms. Eimer made careful and ex-
tended studies of the wing-patterns of two large groups of
butterflies, and of certain lizards and birds, and it is on the
basis of these studies in particular that his theory was
formulated. It is certainly to be admitted that his exhaust-
ive and most suggestive account of the relations of species
and patterns in the swallow-tailed and certain other butter-
flies makes a very strong argument against the validity of
natural selection as an explanation of these conditions. And
the example of Eimer’s prolonged and minute study of

OTHER THEORIES OF SPECIES-FORMING. 285

actual facts as a basis for his theory and hypothesis building
is one which has not been always followed by biological
generalisers. It is to be regretted that the polemical and
personal character of much of Eimer’s writing has tended
to make his whole work less regarded than it ought to be
by biologists.

That Eimer’s theory does not include in any degree the
assumption 0 yn Of an inner ‘directive or. progressive. force the
following quotation from Eimer himself shows: “Accord-
ing to my investigations the chief cause of transformation
[of species] is that determined definitive organic growth
(organophysis) whose expression is a definite determined
development (orthogenesis), which is imposed on the
plasma by constant outer influences, climate, and nourish-
ment. . . . Apart from the fact that the Nagelian assump-
tion of a definite determined development is a hypothetical
one, not proved by facts, the zoologist can hardly accept the
existence of such a dominant inner factor ever pushing
toward advance, when he recalls the host of regressive struc-
tures which he has to see. This tendency to progress based
on the assumption of ‘inner growth laws’ contradicts
flatly the assumption of outer influences as causes of
change. . . . And it is my belief that it is precisely
these outer influences, and the physiological phenomena
dependent on them, which are the determining factors in
the phyletic development just as they are in individual
development.” **

Among American biologists who have been believers, in
some degree, in Lamarckism or some other form of ortho-
genetic evolution, Cope is the one who has most
definitely formulated his beliefs into a complete
theory of the method of creating and guiding
variation and descent lines. Cope’s theory may be called

one of bathmism (growth- -force), Kinetogenesis (direct effect

of use and disuse and environmental influence), and arch-

Cope’s ortho-
genetic theory,

286 DARWINISM TO-DAY.

zsthetism (influence of primitive consciousness). In an
essay’ first published by Cope in 1871 the following
hypotheses were presented. (These hypotheses are stated
here in Cope’s own words, quoted from the preface of his
pook “The Origin of the Fittest,” 1887):

“1. The law of repetitive addition, in which the structures
of animals were shown to have originated from simple
repetitions of identical elements.

“2, The existence of an especial force which exhibits
itself in the growth of organic beings, which was called
growth-force, or bathmism.

“3, That development consists in the location of this
energy at certain parts of the organism.

“4. That this location was accomplished by use or effort,
modifying and being modified by the environment; or the
doctrine of kinetogenesis.

‘“s. That the location of this energy at one point causes its
abstraction from other points, producing ‘complementary
diminution’ of force at the latter.

“6. That the location of this energy, so as to produce the
progressive change called evolution, is due to an influence
called ‘grade influence.’

“7. That inheritance is a transmission of this form of
energy, which builds in precise accord with the sources
from which it is derived.

“8. That this ‘grade influence’ is an expression of the in-
telligence of the animal, which adapts the possessor to the
environment by an ‘intelligent selection.’

“g. An attempt to account for the origin of “mimetic
analogy’ by ‘maternal impressions.’ ”

In later writings ** Cope subdivides his kinetogenesis prin-
ciple, or the influence of use, disuse, and environment, into
a physico-chemical influence affecting the organism through
molecular effects, which he calls physiogenesis, and a me-
chanical influence affecting the organism through molar

OTHER THEORIES OF SPECIES-FORMING. 287

effects, for which the term kinetogenesis is retained. The
modifications produced by these two classes of influences
“are supposed to be the result of the action of the causes in
question continued throughout geologic time.” These
modifications are assumed to be inherited. In the animal
kingdom kinetogenesis, or the modifying influence of mo-
tion, is assumed to be the more potent efficient cause of
evolution; in the plant kingdom, physiogenesis. The. gen-
eral standpoint of Cope’s theory is thus strictly Lamarckian.
But he adds to this reformulation of general Lamarckism a
remarkable feature which he calls archesthetism. This 1s:
the doctrine that ‘‘animal movements are primitively deter-
mined by sensibility or consciousness” and that this “con-
sciousness has been and is one of the primary factors in the
evolution of animal forms.” That is, the kinetogenesis.
which is the chief causo-mechanical factor of the evolution
of the animal kingdom, from primitive single-cell type to
most complex Metazoan, has for its own initiation conscious
effort. Thus Cope is forced to assume, which he does, that
“conscious states have preceded organisms in time and
evolution.” The formal statement of this phenomenon,
then, has to be the thesis that energy can be conscious. “If
true,’ writes Cope, “this is an ultimate fact, neither more
nor less difficult to comprehend than the nature of energy
or matter in their ultimate analyses. But how is such a
hypothesis to be reconciled with the facts of nature, where
consciousness plays a part so infinitesimally small? The
explanation lies close at hand, and has been already referred
to. Energy become automatic is no longer conscious, or is.
about to bécome-nnconseious:””*Cope’ holds then that “con-
sciousness was coincident with the dawn of life,” and that
“evolution is essentially.a process of mind. The source of
the consciousness, which is back of it, is at present an un-
See par eee 3

Cope was a palzontologist,** and his belief in the necessity

288 DARWINISM TO-DAY.

of some factor or factors besides that of natural selection
to explain evolution lines as revealed by paleontological
study is shared by a large majority of the recognised
American paleontologists. Osborn of Columbia, Williston
of Chicago, Hyatt of Boston, Smith of Stanford, studying
respectively the fossil mammals, the reptiles, and the
molluscs, all voice their belief in the existence of evidence in
the history of the evolution of these animal groups for
orthogenetic variation and descent.
Recently Whitman, the Nestor of American zoologists,
has declared himself strongly as an adherent of the actuality
of orthogenetic evolution. For many years
Whitman’s ‘ ‘ ee
expression in | Whitman has been studying the variations and
favour of ortho- inheritance in pigeons, and through this work
at in particular he has become convinced that
species-forming variation does advance in a definite direc-
tion as well as in various directions. He says,’ “natural
selection, orthogenesis,* and mutation appear to present
fundamental contradictions; but I believe that each stands
for truth, and reconciliation is not distant. The so-called
mutations of CEnothera are indubitable facts; but two lead-
ing questions remain to be answered. First, are these muta-
tions now appearing, as is agreed, independently of varia-
tion, nevertheless a production of variations that took place
at an earlier period in the history of these plants? Sec-
ondly, if species can spring into existence at a single leap,
without the assistance of cumulative variations, may they
not also originate with such assistance? That variation
does issue a new species, and that natural selection is a
factor, though not the only factor, in determining results,
is, in my opinion, as certain as that grass grows although
we cannot see it grow. Furthermore, I believe I have
found indubitable evidence of species-forming variation
advancing in a definite direction (orthogenesis), and like-
wise of variations in various directions (amphigenesis). If

OTHER THEORIES OF SPECIES-FORMING. 289

I am not mistaken in this, the reconciliation for natural
selection and orthogenesis is at hand” (p. 4).

In the category of determinate or orthogenetic variation
should be included Delage’s ** not very clearly distinguished
Denese variation générale. “We call by the name of
ory ofgeneral general variation,” he says, “that which appears
wanton at one time in all the individuals of a race or
at least a large number of individuals and which affects,
most often, several characteristics, if not all, in various
degrees of strength. Variations of this sort must be due
to modifications of the germ plasm produced either by the
reducing division, or by fertilisation, or by accidental altera-
tions which this plasm undergoes in its various divisions.”
It is to these variations, according to Delage, that species-
change is due. The inducing influences which result in the
appearance of general variations are use and disuse and the
‘conditions of life’ (nutrition and climate).

As forming a sort of link between the theories of ortho-
genesis and those of heterogenesis (to be discussed in the

ee next chapter), may be mentioned the rather
theory of vague and unformed theory of Jaeckel,”’ the
metakinesiss = Berlin paleontologist, called “metakinesis.”
Jaeckel believes, from a study of fossil animal series, that
there exists evidence of orthogenetic descent, but that while
genera and families may show continuous phyletic series,
specresappéa af sporadically, suddenly, and without special
reference to the phyletic s series. He believes that many cases
of epistasis occur: that is, that many sexually mature ani-
mals show arrests of development in early ontogenetic
stages, and have therefore given up a former further
development. He finds numerous examples of this condi-
tion among fossil crinoids and trilobites and living sela-
chians. What his theory of metakinesis really seems to be
is a combination of the sudden, definitive appearance of new
species, which is the essential conception in the theories of

290 . DARWINISM TO-DAY.

heterogenesis (explained in the next chapter), with the
determinate lines of change or descent, which is the essential
idea in orthogenesis.

APPENDIX,

* Lamarck, 1744-1828, the “founder of the complete modern theory
of descent, is the most important figure [in the history of the

References to theory of evolution] between Aristotle and Darwin”
Lamarck’s (Osborn, ““From the Greeks to Darwin,” p. 156, 1899).
writings. His theory of descent and the causes of descent was
presented in his ‘‘Philosophie Zoologique,” a large work published in
1809. For a brief account of Lamarck’s life and work, see Osborn,
“From the Greeks to Darwin,” pp. 156-181, 1899. For an exhaustive
account with full quotations from Lamarck’s exposition of his the-
ories, see Packard, ‘‘Lamarck, His Life and Work,” 1901. For ex-
positions of the Lamarckian point of view compared with the Dar-
winian position, see Haeckel, E., ““Die Naturanschauung von Darwin,
Goethe, und Lamarck,” 1882; Lang, A., ‘Zur Characteristik der For-
schungswege von Lamarck und Darwin,” 1889; Ward, L. F., ‘““Neo-
Darwinism and Neo-Lamarckism,” Proc. Biol. Soc., Wash., Vol. VI,
pp. 11-71, 1891; Hutton, F. W., “Darwinism and Lamarckism, Old
and New,” 1899; Pauly, A., ““Darwinismus und Lamarckismus,” 1905.

* Among the more conspicuous of these cases are Brown-Séquard’s
epileptic guinea-pigs, Hyatt’s Planorbis shells, Cunningham’s flat-

Brown Rs: fishes, and Fischer’s butterflies. Morgan, in “Evo-
quard’s experi- lution and Adaptation,” gives the following account
ments on guinea- and discussion of the Brown-Séquard experiments
PIES. and results: ‘““The best direct evidence in favour of the
Lamarckian argument is that furnished by the experiments of Brown-
Séquard. He found, as the result of injury to the nervous system of
guinea-pigs, that epilepsy appeared in the adult animal, and that young
born from these epileptic parents became also epileptic. Still more
important was his discovery that, after an operation on the nerves,
as a result of which certain organs, the ear or the leg, for instance,
are affected, the same affection appears in the young born from
such parents. These results of Brown-Séquard have been vouched
for by two of his assistants, and his results in regard to the inheri-
tance of epilepsy have been confirmed by Obersteiner, and by
Luciani on dogs. Equally important is their later confirmation, as
far as the main facts go, by Romanes.

“Brown-Séquard gives the following summary of his results.
I follow Romanes’ translation in his book on ‘Darwin and After

OTHER THEORIES OF SPECIES-FORMING. 291

Darwin, where there is also given a careful analysis of Brown-
Séquard’s results, as well as the outcome of the experiments of
Romanes himself. The summary is as follows :—

“1. ‘Appearance of epilepsy in animals born of parents which had
been rendered epileptic by an injury to the spinal-cord.

“2. ‘Appearance of epilepsy also in animals born of parents
which had been rendered epileptic by section of the sciatic nerve.

“3. “A change in the shape of the ear in animals born of parents
in which such a change was the effect of a division of the cervical
sympathetic nerve.

“a. ‘Partial closure of the eyelids in animals born of parents in
which that state of the eyelids had been caused either by section
of the cervical sympathetic nerve, or the removal of the superior
cervical ganglion.

“se ‘Exophthalmia in animals born of parents in which an injury
to the restiform body had produced that protrusion of the eyeball.
This interesting fact I have witnessed a good many times, and seen
the transmission of the morbid state of the eye continue through
four generations. In these animals modified by heredity, the two
eyes generally protruded, although of the parents usually only one
showed exophthalmia, the lesion having been made in most cases
only on one of the corpora restiformia.

“6. ‘Hematoma and dry gangrene of the ears in animals born
of parents in which these ear alterations had been caused by an
injury to the restiform body near the nib of the calamus.

“7 “Absence of two toes out of the three of the hind-leg, and
sometimes of the three, in animals whose parents had eaten up
their hind-leg toes, which had become anesthetic from a section
of the sciatic nerve alone, or of that nerve and also of the crural.
Sometimes, instead of complete absence of the toes, only a part
of one or two or three was missing in the young, although in
the parent not only the toes, but the whole foot was absent
(partly eaten off, partly destroyed by inflammation, ulceration, or
gangrene).

“8. ‘Appearance of various morbid states of the skin and hair
of the neck and face in animals born of parents having had similar
alterations in the same parts as effects of an injury to the sciatic
nerve.’

“Romanes, who later went over the same ground, in part under
the immediate direction of Brown-Séquard himself, has made some
important observations in regard to these results, many of which
he was able to confirm.

“He did not repeat the experiment of cutting the cord, but he
‘found that, to produce epilepsy, it was only necessary to cut the

292 DARWINISM TO-DAY.

sciatic nerve. The ‘epileptiform habit’ does not appear in the animal
until some time after the operation; it lasts for some weeks or
months, and then disappears. The attacks are not brought on spon-
taneously, but by ‘irritating a small area of the skin behind the
ear on the same side of the body as that on which the sciatic nerve
had been divided.’ The attack lasts for only a few minutes, and
during it the animal is convulsed and unconscious. Romanes thinks
that the injury to the sciatic nerve, or to the spinal cord, produces
some sort of a change in the cerebral centres, ‘and that it is this
change—whatever it is, and in whatever part of the brain it takes
place—which causes the remarkable phenomena in question.’

“In regard to Brown-Séquard’s statements, made in the 3d and
the 4th paragraphs, in respect to the results of the operation of
cutting the cervical sympathetic, Romanes had not confirmed the
results when his manuscript went to press; but soon afterward,
after Romanes’ death, a note was printed in Nature, by Dr. Hill,
announcing that two guinea-pigs from Romanes’ experiment had
been born, ‘both of which exhibited a well-marked droop of the
upper eyelid. These guinea-pigs were the offspring of a male and
female in both of which I had produced for Dr. Romanes, some
months earlier, a droop of the left upper eyelid by division of the left
cervical sympathetic nerve. This result is a corroboration of the
series of Brown-Séquard experiments on the inheritance of acquired
characters.’

‘Romanes states that he also found that injury to a particular
spot of the restiform bodies is quickly followed by a protrusion
of the eye on the same side, and further, that he had ‘also had
many cases in which some of the progeny of parents thus affected
have shown considerable protrusion of the eyeballs of both sides,
and this seemingly abnormal protrusion has occasionally been
transmitted to the next generation. Nevertheless, I am far from
satisfied that this latter fact is anything more than an accidental
coincidence. This reservation is made on the ground that the
protrusion in the young is never so great as in the parents, and
also because there is amongst guinea-pigs a considerable amount
of individual variation in the degree of prominence of the eye-
balls. Romanes, while unwilling to deny that an ‘obviously abnor-
mal amount of protrusion, due to the operation, may be inherited
in lesser degree,’ is also unwilling to affirm so important a conclu-
sion on the basis of these experiments alone.

“In regard to Brown-Séquard’s 6th statement, Romanes found
after injury to the restiform body that hematoma and dry gan-
grene may supervene, either several weeks after the operation, or
at any subsequent time, even many months afterward. The disease

OTHER THEORIES OF SPECIES-FORMING. 293

usually affects the upper parts of both ears, and may then gradually
extend downward until nearly the whole ear is involved. ‘As re-
gards the progeny of animals thus affected in some cases, but by
no means in all, a similarly morbid state of the ears may arise
apparently at any time in the life history of the individual. But
I have observed that in cases where two or more individuals of the
same litter develop this diseased condition, they usually do so at
about the same time, even though this may be months after birth,
and therefore after the animals are fully grown.’ Moreover, the
morbid process never extends so far in the young as it does in the
parents, and ‘it almost always affects the middle third of the ear.’
Several of the progeny from this first generation, which had appa-
rently inherited the disease, but had not themselves been directly
operated upon, showed a portion of the ear consumed apparently
by the same disease. Romanes then gives the following signifi-
cant analysis of this result. Since a different part of the ear
of the progeny is affected, and also a ‘very much less quantity
thereof, it might seem that the result was due either to a mere
coincidence, or to the transmission of microbes. But he goes on
to say, that he fairly well excluded both of these possibilities, for,
in the first place, he has never observed ‘the very peculiar process
in the ears, or in any other parts of guinea-pigs which have neither
themselves had the restiform bodies injured, nor been born of
parents thus mutilated.’ In regard to microbes, Romanes tried to
infect the ears of normal guinea-pigs by first scarifying these parts,
and then rubbing them with the diseased surfaces of the ears of
affected guinea-pigs. In not a single case was the disease produced.

“Romanes concludes that these ‘results in large measure corrobo-
rate the statements of Brown-Séquard; and it is only fair to add
that he told me they were the results which he had himself obtained
most frequently, but that he had also met with many cases where the
diseased condition of the ears in parents affected the same parts in
their progeny and also occurred in more equal degrees.’

“We come now to the remarkable conclusion given in Brown-
Séquard’s 7th statement, in regard to the absence of toes in animals
whose parents had eaten off their own hind toes and even parts
of their legs. Romanes got neuroses in the animals operated upon,
and found that the toes might be eaten off; but none of the young
showed any defect in these parts. Furthermore, Romanes repeated
the same operation upon the descendants through six successive
generations, so as to produce, if possible, a cumulative effect, but no
inheritance of the mutilation was observed. ‘On the other hand,
Brown-Séquard informed me that he had observed this inherited
absence of toes only in about one or two per cent. of cases.’ It is

294 DARWINISM TO-DAY.

possible, therefore, Romanes adds, that his own experiments were
not sufficiently numerous to have obtained such cases.

“In this connection I may give an account of some observa-
tions that I made while carrying out some experiments in telegony
with mice. I found in one litter of mice that when the young came
out of the nest they were tailless. The same thing happened again
when the second litter was produced, but this time I made my
observation sooner, and examined the young mice immediately after
birth. I found that the mother had bitten off, and presumably
eaten, the tails of her offspring at the time of birth. Had I been
carrying on a series of experiments to see if, when the tails of the
parents were cut off, the young inherit the defect, I might have
been led into the error of supposing that I had found such a case in
these mice. If this idiosyncrasy of the mother had reappeared in
any of her descendants, the tails might have disappeared in suc-
ceeding generations. This perversion of the maternal instincts is
not difficult to understand, when we recall that the female mouse
bites off the navel-string of each of her young as they are born,
and at the same time eats the afterbirth. Her instinct was carried
further in this case, and the projecting tail was also removed.

“Is it not possible that something of this sort took place in
Brown-Séquard’s experiment? The fact that the adults had eaten
off their own feet might be brought forward to indicate the possi-
bility of a perverted instinct in this case also. At least my obser-
vation shows a possible source of error that must be guarded
against in future work on this subject.

“In regard to the 8th statement of Brown-Séquard, as to various
morbid states of the skin, Romanes did not test this, because the
facts which it alleges did not seem of a sufficiently definite character.

“These experiments of Brown-Séquard, and of those who have
repeated them, may appear to give a brilliant experimental confirma-
tion of the Lamarckian position; yet I think, if I were a Lamarckian,
I should feel very uncomfortable to have the best evidence in sup-
port of the theory come from this source, because there are a
number of facts in the results that make them appear as though
they might, after all, be the outcome of a transmitted disease, as
Weismann claims, rather than the inheritance of an acquired char-
acter. Until we know more of the pathology of epilepsy, it may
be well not to lay too great emphasis on these experiments. It
should not be overlooked that during the long time that the embryo
is nourished in the uterus of the mother, there is ample opportu-
nity given for the transmission of material, or possibly even of
bacteria. If it should prove true that epilepsy is due to some sub-
stance present in the nervous system, such substances could get

OTHER THEORIES OF SPECIES-FORMING. 295

there during the uterine life of the embryo. Even if this were the
case, it may be claimed that it does not give an explanation of the
local reappearance of the disease in the offspring. But here, also,
we must be on our guard, for it is possible that only certain regions
of the body are susceptible to a given disease; and it has by no
means been shown that the local defect itself is inherited, but only
the disease. Romanes insists that a very special operation is neces-
sary to bring about certain forms of transmission.”

The case of the Planorbis shells studied by Hyatt (Proc. Amer.
Phil. Soc., Vol. XXXII, p. 615 ff.) has been interestingly dis-

Hyatt’s studies cussed by Le Dantec (“Traité de Biologie,” pp. 296
of Planorbis. ff.. 1903) as follows: ‘On trouve, dans les terrains
trés anciens, des coquilles de Céphalopodes qui ont la forme d’une
corne de vache et dont la section transversale est 4 peu pres circu-
laire; en suivant la série des fossiles de cette catégorie dans
des terrains plus récents, on constate que ces coquilles, presque
droites naguére, se sont enroulées de plus en plus a la maniere
dune spirale d’Archiméde; nous ne connaissons pas la raison
de cette transformation, mais la présence de certains caractéres
communs permet de considérer comme démontré que les formes
enroulées descendent des animaux a coquilles droites. Or, l’enroule-
ment est tellement fort dans certains types que les tours de
spire successifs s'impriment les uns dans les autres, donnant nais-
sance a un sillon dorsal dont la genése mécanique est évidente,
puisqu’il résulte sans conteste de la pression du tour de spire
précédent sur le suivant.

“Tant que les animaux en question restent aussi nettement
enroulés, on peut admettre que ce caractére de l’existence d’un sillon
dorsal est acquis individuellement par chaque Céphalopode pour des
raisons mécaniques évidentes, le contact des tours de spires.

“Mais voila qu’a une période plus récente de l’histoire du monde,
les découvertes paléontologiques nous montrent que les descendants
de ces Céphalopodes a coquille enroulée ont subi un commencement
de déroulement et ont maintenant la forme d’une spirale d’Archi-
mede a tours de spires plus écartés les uns des autres et ne se
touchant plus; et notez bien que des caractéres communs permettent
d’affrmer que ces Céphalopodes a moitié déroulés descendent de
ceux dont l’enroulement était beaucoup plus serré.

“Or, chose admirable, le sillon dorsal persiste chez ces étres a
coque a moitié déroulée! Cependant il n’y a plus maintenant
pression d’un tour de spire sur le tour de spire précédent; nous
avons compris mécaniquement la genése de ce sillon dorsal, quand
les tours de spire se touchaient et se pressaient l’un l’autre; et ce
sillon persiste en dehors des conditions mécaniques ot il a été

296 DARWINISM TO-DAY.

d’abord produit; il se transmet a des descendants dont la coquille
est déroulée! C’est donc que le patrimoine héréditaire a été
modifié sous Vinfluence de la production mécanique de ce sillon
dorsal, au point de devenir adéquat a cette forme nouvelle d’équi-
libre; il y a un nouveau patrimoine héréditaire, qui construisant un
individu nouveau et son squelette, fera apparaitre, sans pression,
le sillon dorsal!”

The results of the experiments of Cunningham on flatfishes are
stated by the author, in a paper on “The Problem of Variation,”
Nat. Sci., Vol. III, p. 285, 1893. Cunningham put the very young
fish, while still bilaterally symmetrical (in which stage the pigment
is equally developed on both sides of the body), into aquaria lighted
from below. He found that when the young fish begins to undergo
its metamorphosis, the pigment gradually disappears on one side,
as it would have done under normal conditions, 7. e., when they are
lighted from above. If, however, the fish are kept for a short time
longer, lighted from below, the pigment begins to come back again.
“The first fact,” says Cunningham, “proves that the disappearance
of the pigment-cells from the lower side in the metamorphosis is a
hereditary character, and not a change produced in each individual
by the withdrawal of the lower side from the action of the light.
On the other hand, the experiments show that the absence of pig-
ment-cells from the lower side throughout life is due to the fact that
light does not act upon that side, for, when it is allowed to act,
pigment-cells appear. It seems to me that the only reasonable con-
clusion from these facts is that the disappearance of the pigment-
cells was originally due to the absence of light, and that the change
has now become hereditary. The pigment-cells produced by the
action of light on the lower side are in all respects similar to
those normally present on the upper side of the fish. If the dis-
appearance of the pigment-cells was due entirely to the variation
of the germ-plasm, no external influences could cause them to re-
appear; and if there were no hereditary tendency, the coloration
of the lower side of the flatfish would be rapid and complete.”

Concerning Fischer’s highly interesting experimental work, I
quote the following paragraph from Fuchs, H. (Biol. Centralbl.,

Fischer’sex- Vol. XXI, pp. 591-592, 1901; Fischer’s own papers
periments with have been published in various biological journals,

butterflies. the particular one recounting the results obtained
with Arctia caja in the Allg. Zeitschr. fir Entomologie, Vol.
VI, 1902):

“Experimentelle Untersuchungen, ob es moglich sei, durch will-
kurliche, geeignet gewahlte Veranderungen der ‘ausseren Lebens-
bedingungen,’ besonders der Temperaturverhaltnisse, im Tierreiche

OTHER THEORIES OF SPECIES-FORMING. 207

Variationen bei den Arten hervorzurufen, wurden in den letzten.
Decennien wiederholt angestellt; mit Vorliebe hat man sich dabei
als Versuchsobjekte die Schmetterlinge gewahlt: ich erinnere z..
B. an die schonen Versuche von Standfuss und E. Fischer. Das
Resultat war—wie ja nach unseren heutigen Anschauungen wtber
den ziichtenden Einfluss der Faktoren der Aussenwelt auf alle
Organismen eigentlich kaum anders zu erwarten stand—positiv.
Eine Frage allerdings, an welche bei diesen Untersuchungen wohl
jeder der Forscher dachte, namlich: ob die auf solche Weise
erworbenen Eigenschaften und Abanderungen auch auf die eventu--
ellen Nachkommen iibertragen, also vererbt wurden oder doch
wenigstens werden konnten, blieb dabei einstweilen unentschieden.
Erst kiirzlich gelang es E. Fischer, auch fiir dieses Postulat der
modernen Biologie einen vollgiltigen Beweis beizubringen. F. expe-
rimentierte mit Arctia caja, dem braunen Bar, der ja auch den
meisten Laien—meist wohl unter dem Namen ‘deutscher Bar’—
bekannt sein durfte, ein erfahrungsgemass fiir kunstliche Varia-
tionsversuche besonders geeignetes Tier. Durch willktrlich ge-
wahlte Temperaturveranderungen, und zwar durch intermittierende
Abktthlungen bis auf—8° C., denen die Puppen wiederholt ausge-
setzt wurden, erzielte F. stark aberrative Falter, und zwar aberrativ
nicht nur beztiglich der ‘Farbe und Zeichnung’—wenn auch hier in
erster Linie—sondern auch beztiglich der Form, z. B. der Flugel
und der Beine. Dabei hebt F. ausdriicklich hervor, dass in letzterer
Hinsicht es sich nicht etwa um Verkruppelungen handelte, sondern
‘die Fiisse waren kraftig und mit gut ausgebildeten Krallen
versehen. Unter diesen Varietaten gelangen nun mehrfache
Kreuzungen; die Puppen dieser Zucht wurden unter normalen
Bedingungen erhalten. Und siehe! von den alsbald ausgeschlupften
Tieren zeigte eine nicht unerhebliche Anzahl die Variationen der
Eltern, und zwar im allgemeinen als Kombinationen aus den
veranderten Eigenschaften beider Eltern, so dass einige mehr dem
elterlichen Mannchen glichen, andere mehr dem elterlichen Weib-
chen. Es ist dieses also, wie F. sagt, ein experimenteller Beweis,
dass:

“Tt. die Art durch die Faktoren der Aussenwelt Veranderungen.
erfahrt, und dass

“2. diese Veranderungen sich auf die Nachkommen wtbertragen.

“Die Thatsache der Vererbung erworbener Eigenschaften steht.
mithin fest, wenn wir auch tiber das Wesen der ratselhaften dabei
stattfindenden Vorgange, auf Grund dieser Untersuchungen, natiir-
lich absolut noch nichts sagen k6nnen.”

To the above cases of the alleged inheritance of acquired charac-
ters I may add some account of certain éxperiments with the mul-

298 DARWINISM TO-DAY.

berry silkworm carried on by R. G. Bell and myself. (For detailed ac-
count of this work see Science, N. S., Vol. XVIII, pp. 741-748, 1903.)

“One of the races of the mulberry silkworm, Bombyx mori, has
been the subject of experiments directed toward a determination of
the exact quantitative relation which quantity and quality of food
bear to the development and variations of the individual insect and
its progeny. ...

“The insect, Bombyx mori, has a complete metamorphosis, tak-
ing no food as an adult, so that the experimental control of the

Experiments feeding has been necessary only during the larval or
with silkworms. ‘silkworm’ stage. The larval life is subdivided into
five stages clearly set off from one another by the intervening
moults, of which there are normally four, and these substages have
been useful when an alteration of food conditions during a sharply de-
fined shorter time than the entire larval life was desirable... . The
change in quantity of food has consisted in altering the amount of
mulberry leaf served to the larve, the control of which has been
secured as follows: It has been determined through experience with
normal larve that each will consume a certain amount of food in
a certain number of hours (increasing in amount with the increas-
ing age and size of the larva), this amount representing the
optimum amount of food for the normal individual and necessitating
as many daily meals as are required to keep any but the moulting
larva constantly supplied with fresh food. This amount determined,
a tolerably definite small proportion of the optimum amount has
been allotted the individuals which were sentenced to short rations,
which, roughly speaking, might be listed as one-quarter the optimum
amount during earlier stages and one-eighth during the late larval
stages. This one-fourth, one-eighth, or whatever it may have been
numerically, was, at any rate, as small an amount of food as was
compatible with mere life. ...

“These experiments have extended over a period of three years,
covering as many generations of the insect. The data gathered
(being the measurements, weight, and duration of each larva in each
of its five states; the time of spinning, weight of silk and weight
and duration of each pupa; and the weight, size, pattern, and
fertility of female of each imago) furnish material, then, for a
study of the effects of under-feeding upon individuals during a
single generation (the 1903 generation or that of 1902 or Igor),
during two successive generations (1901-02 or 1902-03), and two
alternating generations (1g0I-1903) and during three generations
(1901-03), a control lot having been carried for each experimental
lot so that what is ee may confidently be distinguished from
what is normal.

OTHER THEORIES OF SPECIES-FORMING. 299

“In these variously-fed worms there exists a very definite and
constant relation between amount of food and size as indicated by
weight, the starveling individuals being consistently smaller than
the well-nourished, the lingering effects of this dwarfing being
handed down even unto the third generation, although the progeny
of the famine generation be fed the optimum amount of food; in
case the diminished nourishment is imposed upon three, or even
two successive generations, there is produced a diminutive, but
still fertile, race of Lilliputian silkworms, whose moths, as regards
wing expanse, might join the ranks of the micro-Lepidoptera
almost unremarked.

“In illustration may be quoted the typical or modal larval weights
for each of the lots of 1903 at the time of readiness to spin, which
marks the completion of the feeding and is, therefore, an advan-
tageous point for a summary of the results of the three years’
experimental feeding.

“The history of the eight lots referred to may be gathered from
an examination of the accompanying table, in which ‘O’ means
optimum amount of food and ‘S’ means short rations. The column
to the right indicates the relative rank of the various lots as judged
by the modes of frequency polygons erected to include all the
individual weights for each lot at spinning time.

HISTORY OF LOTs.
Lot Number. Modal Rank.
Igor. 1902. soo"
Grandparents.|Grandparents. Paeo
eee ee ee eee! O O O I
aR 5 ee ne O O S) 6
de aey a pig hin'S) 4&4. O S O 3
LEYS oe ee rae O S S 7
eS aie ahs eile\e4 5. Ss O O 2
[2 Ry uee at oar are eR Ss O Ss 5
“a RT te or ee S) S O 4
SRO Ser Sone noe ee Ss S Ss 8

“We find that control lot 1, consisting of normally-fed indi-
viduals of normal ancestry, holds first rank in weight, as was to be
expected. Second comes lot 5, whose grandparents experienced a
famine but whose parents as well as themselves enjoyed years of
plenty. Lots 2 and 3 have likewise had one ancestral generation on
Short rations, and the fact that they are lighter in weight than lot

300 DARWINISM TO-DAY.

5 illustrates a general rule which obtains throughout the entire
company of experimental worms, namely, that the effects of famine
grow less evident the further removed the individuals are from its.
occurrence in their ancestral history. Thus lot 5 is two generations.
removed from the famine of 1901, while lot 3 has had but one
generation in which to recover its ancestral loss. Lot 2, which
has had a total of but one famine year—the current year—neverthe-
less ranks below lot 7, which has had two famine years in its
ancestry succeeded by plenty during the current year. Lot 2 also
ranks below lot 6, a fact which appears strange, considering that
lot 6 has suffered two generations of famine, including the current
year, which is the only famine year experienced by lot 2. In
explanation of this anomalous condition it is suggested that possibly
the larve of lot 6 were better fitted for enduring and making the
best of hard conditions than were the individuals of lot 2, the
ancestors of the former lot having been selected two years ago
on a food-scarcity basis. This suggestion gathers support from an
inspection of the mortality notes, from which it appears that the
number of deaths—for which the famine was probably a contributing
and not a primary cause—in each lot which is for the first time
subjected to short rations is almost doubly greater than the num-
ber of deaths in lots which are descended from starved ancestors,
whether these ancestral famines occurred in successive or alternate
years. The figures indicate that a reduction of food is almost twice
as destructive upon the first generation which is subjected to it as
it is when visited on a second generation. Lot 4 follows lot 2 as
the seventh in rank and its position is in accord with the rule above
noted, its latest ancestral generation which enjoyed an optimum
amount of food during 1902 or 1903. Lot 8 holds lowest rank,
it and its ancestors having been subject to trying conditions through-
out the entire three years, during some one or two of which all
the other lots have enjoyed the best of food conditions. Thus it
appears that a generation of famine leaves its impression upon at
least the three generations which succeed it, yet the power of
recovery through generous feeding exhibited by the progeny of
individuals subjected to famine, is so extensive (witness lot 5)
that it appears probable that every trace left by the famine upon
the race would eventually disappear. It is even conceivable that the
ultimate result of the famine would be a strengthening of the race,
the famine having acted the part of a selective agent, preserving
only the strong.

“But although there is a large difference between the well fed
and the poorly fed, there persists, more obviously in late than in
early life, a very considerable discrepancy as to size among the

OTHER THEORIES OF SPECIES-FORMING. 301

individuals of each single lot whose environment, in so far as food,
temperature, room, humidity, etc., constitute it, is identical.

“For example, referring again to the weights at spinning time of
the larve of 1903, it is true that, although each lot has a modal
class of weights to which the majority of its individuals belong and
about which the rest of the lot distributes itself rather symmetrically,
the extremes are surprisingly distant from one another. Thus in
lot 1 (the normal control lot) the extremes are 1,540 and 2,530
mg.; in lot 2,* 800 and 1,402 mg.; in lot 3, 1,180 and 2,170 mg.;
in lot 4, 690 and 1,204 mg.; in lot 5, 1,370 and 2,100 mg.

“That is to say, identical feeding has not made identical full-
‘grown larve out of individuals which undoubtedly varied congent-
tally at the start, those variations—in embryo—standing at birth in
the same relation to one another that they stand in the adults, hav-
ing merely been smaller and less readily discernible in early life,
although manifestly present in delicately measurable degree in the
earliest records made upon normal individuals. For example,
weight measurements taken immediately after the second moult,
range in one lot from 21 to 39 mg., or 60 per cent. of the modal
weight, while the weights in this same lot at spinning time, some
five weeks later, range from 534 to 2,080 mg., or 85 per cent. of
the mode for the lot. These embryonic but potentially large varia-
tions have simply ‘grown up’ along with the insect and are as truly
congenital in the adult as they were in the newly hatched larva.
This would seem to place quite conclusively in the category of
congenital variations some part of those variations (in size and pro-
portions of parts) which are commonly, and properly to some
degree, called acquired.

“That conditions of alimentation bear a directive relation to func-
tional activity, may be demonstrated by reference to the records of
the physiological functions of moulting, spinning, pupating, and
emerging, of the individuals of the experimental lots.

“An abnormal extension of the time needed for the metamor-
phosis follows upon a reduction of the food supply. The degree
of extension depends with the utmost nicety upon the amount of
food given the larve. For example, among the Igor generation of
‘silkworms, one control lot of twenty larve was given the optimum
amount of food, a second lot of twenty larve one-half this amount,
and a third lot of twenty larve one-quarter of the amount. To
take the time of the fourth moulting as an illustration, the moulting
was begun by the first lot, which led the way by two and a half
days, at the end of which the second lot began to moult, while

* See table, next page, for the history of each lot.

302 _ DARWINISM TO-DAY.

the third lot was twenty-four hours behind the second. All the
individuals of the first lot had finished moulting on April 20, all
of the second on April 24, while the moulting in the third lot con-
tinued until April 29.

“As in the matter of weight, this retarding of the functions, by
means of a reduced food supply, affects not only the immediate
generation which is subjected to the famine, but the lingering effects
of it may be traced in the progeny of the dwarfed individuals at
least unto the third generation, even though two years of plenty
follow the one year of famine. The conditions which obtain in
each lot of individuals of the 1903 generation at spinning time are
shown in the accompanying table, which is based upon polygons
erected to include all the individuals in each lot.

RANK OF 1903 LOTS AS TO PROMPTNESS
IN SPINNING.
HISTORY OF LOTS.
Lot When Two-thirds of Each Lot
Num- were Spinning.
ber, P
Earliest
ree Spinner. a ee
nee 1902. n Order ates
Bee Parents.| 19°93 Date. | of Rank. Spinner.
Micke O O O I May 12 I I
ae O O S 5 9m 4 4
a O S O 2 pe 4 2 3
Pee O Ss SS) 4 a) ae 5 5
Coes Ss O O 3 lle 2 2
ti S O S 6 ‘> ae 6 |
ee S) Ss O 6 “22 3 5
Roxx cas S S 7 te: 90 7 6

“This period in the life of the silkworms is particularly advan-
tageous for consideration here, because it marks the completion
of the feeding, so that the individuals of under-fed ancestry have
been given the best chance to recover, while those subject to altered
food conditions, had had the benefit of the alteration during the
entire food-taking period of life.

“In the table, ‘O’ means optimum amount of food, and ‘S’ means.
short rations. To the right of the history of the lots is a section
showing the rank of the lots as to the extreme time limits of the
spinning time (emphasised congenital differences again), with a
safer criterion, as to their relative promptness, in the column be-
tween the extremes—a column of figures intended to show the rela-
tive promptness with which a two-thirds majority of the larve

OTHER THEORIES OF SPECIES-FORMING. 303

in each lot arrives at the spinning time, this proportion being taken
to represent the typical condition for the lot. The order in which
the lots are arranged in this column corresponds in a general way
with that prevalent for the weights at spinning time, and the
generalisations indulged in there may, with few exceptions, be
applied here. The lots which were well fed during the 1903
generation are ahead of all of those given short rations in 1903,
whatever ancestry they may have had. Lot 1 leads here as in the
matter of weight. Lots 3 and 5 tie for second place, having held
second and third places in weight. Lots 2 and q stand in the
same relation to one another that they held as to weight. Con-
trary to the weight relation, lot 6 follows lot 2 at the spinning—a
fact which illustrates again the general rule that two generations
of famine are more disastrous than one, but does not lend support
to the notion of natural selection on a food scarcity basis as pre-
viously suggested. Lot 8, which has had no relief from famine
during the entire three years, brings up the rear at the spinning,
as might be expected.

“This check upon functional activity exercised by diminished nour-
ishment affects the moulting, the time for the commencement of
spinning, and the issuing time for the adults, but the time spent
in the spinning of the cocoon, from its beginnings in the threads
of the supporting net to its apparent completion when the cocoon
becomes opaque, is practically identical for under-fed and well-
fed individuals. A reason for this exception to the tardy habits.
of the under-fed is to be found in the fact that the under-fed
larve produce less silk (less in size, thickness, and weight) than the
well-fed, thus accomplishing more meager results in the same
amount of time. That the individuals sentenced to short rations.
should produce less silk than their well-fed neighbours is certainly
to be expected, silk not being made without leaves any more
readily than bricks without straw.

“Not only do short rations protract the time appointed for the
spinning, moulting, etc., but they appear to have a more striking
effect upon the actual occurrence of the moulting. The normal
number of moults for the silkworm larva is four. Five moults
have occurred for most of the individuals belonging to the under-
fed lots of 1902 and 1903, whereas none of the well-fed individuals
has undergone a fifth moult. It would seem, therefore, that the
occurrence of a fifth moult may be fairly ascribed to a reduction of
food; at least a fifth moult very frequently accompanies it and has
suggested the possibility that the enforced fasting of the under-
fed larva—in the intervals between meals—may have the same
physiological effect as the normal fasting which precedes the normal

304 DARWINISM TO-DAY.

moulting, during which time the so-called ‘moulting fluid’ is
secreted. That this effect may accumulate throughout the life-
time of the larva until the larva is actually forced to indulge in the
extravagance (of strength, feeding time, and body wall material)
of an additional moult is conceivable and will justify a further
“Lest,

“As to the life-and-death selection due to famine, it may be
said, in addition to the previous discussion of mortality among
the experimental silkworms, that while lots subjected to two years
of famine (themselves in one year, their parents in the year before)
were fertile in so far as number of young hatched is concerned, it
was found to be exceedingly difficult to rear from them a 1903
generation. Indeed, at the time of the second moulting there were
but nineteen individuals (and tolerably vigorous larve they were)
alive in the lot which had experienced two years of famine, al-
though every individual of the 149 hatched was carefully preserved
and royally fed—a fact which goes to prove that the equipment at
birth of many of these larve was inadequate.

“The fact that some larve of starved ancestry have exhibited a
superiority over their fellows, in surviving and recovering from
hard conditions, is testimony for the existence of individual varia-
tions which cannot be defined anatomically, and yet which serve as
‘handles’ for natural selective agents. Such variations might be
called physiological variations, since it seems that the surviving
larve must be those which are in best trim physiologically. These
larve are able to make the most of the food offered to them. If
competition were allowed, they would probably be the individuals
which would cover the area most rapidly, securing whatever food
there might be. But under our experimental conditions there was
no competition allowed and yet certain precocious individuals made
more grams of flesh and more yards of silk, than other larve
furnished with the same amount of raw material under like con-
ditions; that this was due to the possession by the former of certain
congenital qualities of adaptability can scarcely be doubted.

“As to the fertility of the variously fed lots, in so far as number
of eggs produced is a measure of fertility, our records already
demonstrate the fact that the better nourished are the more fertile.
Furthermore, the economy in this matter practised by the starve-
lings is not merely numerical, quality as well as quantity of eggs
being affected. In witness of this point may be recalled the story
of the dying 1903 generation, produced from eggs of the starvelings
of 1901 and 1902, which would seem to offer conclusive evidence
that a famine suffered by the parents works its way into the germ-
cells so that most of their progeny have but a poor birthright.”

“2 .

m +
ie ge
ae
|
re

OTHER THEORIES OF SPECIES-FORMING. 3°95

For special discussions of the inheritance of acquired characters,
see the following: Roth, E., “Die Thatsachen der Vererbung,” 1885 ;
Ziegler, E., “Konnen erworbene pathologische Eigenschaften ver-
erbt werden und. wie entstehen erbliche Krankheiten und Missbil-
dungen,” 1886; Rohde, F., “Uber den gegenwirtigen Stand der
Frage nach der Entstehung und Vererbung individuellen Eigen-
schaften und Krankheiten,” 1896; Osborn, H. F., “Are Acquired
Variations Inherited,’ 1890; Elliott, D. G., “The Inheritance of
Acquired Characters,” Auk, Vol. IX, pp. 77-104, 1892; Packard, A.
S., “On the Inheritance of Acquired Characters in Animals with
Complete Metamorphosis,” Proc. Amer. Acad. Science, pp. 331-
370, 1894; Ritter, W. E. “On the Nature of Heredity and
Acquired Characters, and the Question of the Transmissibility of
these Characters,’ 1900; Wettstein, R. von, ‘Der Neo-Lamarckis-
mus und seine Beziehungen zum Darwinismus,” 1903; Detto, Carl,
“Theorie der direkten Anpassung,’ 1904 (good bibliography of
papers on plant adaptations); Lendenfeld, R. V., “Variation and
Selection,” Biol. Centralbl., Vol. XXIII, p. 480 ff., and p. 563 ff.,
1903; Pauly A., ‘“Darwinismus und Lamarckismus,” 1905; Lotsy,
J. P., “Vorlesungen tiber Descendenztheorien,’ Vol. I, chap. xii,
1906; Wheeler, W. M., “The Polymorphism of Ants,” Bull. of
Amer. Mus. Nat. Hist., Vol. XXIII, pp. 1-93, Plate I-VI, January,
1907 (see especially pp. 50-90). Certain writers of sociologic and
philosophic interests, have discussed especially the possibility of the
inheritance of acquired mental capacities or qualities in man; ex-
pressing a belief in such inheritance are Biichner, “Die Macht der
Vererbung und ihr Einfluss auf der moralischen und geistigen
Fortschritt der Menschheit,’ 1882, and Hartmann, E. V., ‘“Philo-
sophie des Unbewussten,” roth ed.; against such an inheritance is
Rawitz, B., “Urgeschichte, Geschichte, und Politik,” 1903. Most
important of all the discussions of the inheritance of acquired char-
acters are those of Weismann, Spencer, and Eimer.

A recent American champion of Lamarckism is Caspar L. Red-
field, in whose writings (‘‘Control of Heredity,’ 1903, “Evolution

Redfield’s of the Setter,” in American Field, 1904 and 1905, and
position. “Breeding of the Trotter,’ in The Horseman, 1905)
is urged the doctrine that acquired mental and dynamic qualities are
inherited. On a host of data, derived from the pedigrees and
records of trotting horses and setter dogs, Redfield keenly works out
his inductions regarding the inheritance by young of the special
qualities due to training and practice (acquirement) of the parents;
that is, the best offspring (from the sportsman breeder’s point of
view) come from the best trained parents. There is a great deal
of ammunition for the advocates of Lamarckism in Redfield’s

306 DARWINISM TO-DAY.

records, although his too sharp distinction between structural and
functional (so-called “dynamic’’) characters is not at all helpful.

The most recent serious treatment of the problem from the neo-
Lamarckian side, and one of great interest and real force, is that

Montgomery's of Montgomery in his book on “The Analysis of
explanation of Racial Descent in Animals” (1906). Montgomery
inheritance of contends that there can be no congenital variation
Variation, without external stimuli (or hybridisation) to initiate
it, because germ-plasm cannot be assumed to set up change inde-
pendently and automatically, as this would be almost like the
assumption of spontaneous generation. Montgomery says, “When
the process of heredity proceeds unchanged the ontogeny of one
individual is just like that of its parent. When a change of the
ontogeny occurs, so that the offspring comes to be different from
its parent, we say that a variation has appeared in the offspring.
This variation, it is thinkable, may have been produced: (1) by
internal growth energies, (2) by external environmental influences,
or (3) by a combination of both; and it is necessary to discuss
which one of these is the most probable.

“There is clearly, in the process of production of variation and
mutation, some modification of the normal process of heredity.
Since in a number of species it has been shown that all the adult
individuals from one locality are not exactly alike, but show meas-
urable differences in dimensions, colour, or some other character,
it follows that the hereditary process of each such individual must.
vary correspondingly, even though the variation does not become:
perceptible until the stage of maturity. The origin of inherited
variation or mutation is then a question of the origin of modifica-
tion of the hereditary process.

“The regularity of the process of heredity is quite comprehensi-
ble on the basis of the direct transmission of definite chromosomes
in number, form, and quality constant for the species. From cell
to cell, from individual to individual, these chromosomes are regu-
larly transmitted in a continuous progress, therefore a succession of
similar individuals is quite understandable. One germ-cell comes
from a preceding one, to our knowledge is never formed from a
specialised tissue-cell, so that there is an uninterrupted passage of
the germ-plasm through the race. This is Weismann’s idea of the
continuity of the germ-plasm, which we will paraphrase as the
continuity of the chromosomes.

“A variation to become inherited must then be referable to a
modification of the energies of this germ-plasm. The germ-plasm
is living substance of proved great importance in the metabolism of
the cell. Though in a sense it appears, from microchemical re--

OTHER THEORIES OF SPECIES-FORMING. 307

searches, to be the chief agent in constructive processes of the cell,
it equally appears to be incapable of life, or unable to act in a
normal manner, when removed from the influence of other cell
substances. The food required by a germ-cell for its growth is
obtained from without the cell, and must pass through the cytoplasm,
in more or less changed condition, to reach the chromatin within
the nucleus and there be elaborated into living substance and
passed over to the cytoplasm in other form. This conclusion is
drawn from both experimental and microchemical studies. So the
oxygen required by the cell, and the water, must be obtained from
without the cell. This is simply in agreement with the general
principle that no body can increase in mass, circumambient condi-
tions remaining unchanged, without accretions from _ outside.
Therefore, the germ-plasm does not so much create new substances
as it changes substances brought to it. It and the other cell con-
stituents are harmoniously and mutually interdependent, and the
ultimate source of energies of these substances, all connected with
the elaboration of living matter, is referable to external agencies
because referable to food.

“This being the case, the energies of the hereditable substance,
the germ-plasm, are clearly dependent upon influences of the envi-
ronment. This conclusion is not at all in contradiction with the
idea of the continuity of the chromosomes, as we pointed out in
the preceding chapter. Therefore, Weismann was in error when, to
support his idea of the continuity of the germ-plasm, he at first
argued the energies of the germ-plasm to be independent of body
cells and of the environment generally. His supposition was both
unnecessary for the view of the continuity, and also out of agree-
ment with the phenomena. The ovum cannot elaborate its yolk
substance except out of food substance received from without;
the amount of its food substance will depend upon the state of
nutritive metabolism of the individual carrying the egg-cell; starva-
tion of that individual will cause cessation of energy in the germ-

cell, and ligaturing of the blood-vessels supplying the ovary will

produce death of the egg-cells. The results of observational expe-
rience teach that the germ-plasm is not a little god, capable of self-
existence without respect to external agencies, but is very intimately
bonded to the latter. Whether the germ-cell, as in the sponges, be
an amoeboid cell which wanders about in the body tissues, or
whether it is immovably held in place by tissue-cells, it is impossi-
ble that it can live and grow without receiving and reacting to
stimuli from these tissue-cells. The egg-cells of many animals are
set free in water before they commence to cleave into embryonic
cells; how can we say, then, that the conditions in the water do

308 DARWINISM TO-DAY.

not influence them? They will die if removed from the water, and
develop abnormally if certain substances be added to or subtracted
from the water. But the embryonic differentiation is a result of
chromosomal activities, as we have seen; therefore, changes in the
medium must influence the germ-plasm. Is not a well-recognised
characteristic of living matter, response to external stimuli? How
can any living cell be acted upon by stimuli and yet not react to
them? There is not a single observation to show that any germ-
cell, or its germ-plasm, is in any way guarded or protected from
external stimuli, either by the structure of its cell wall or peripheral
cytoplasm, or by the nature of the living tissue that encloses it.
And whatever affects the cell body must indirectly affect the
chromosomes, because of the physiological connection of the two.

“From such considerations it would seem practically certain that
the energies of the chromosomes are to some extent respondent to
environmental stimuli. And since observation shows that living
matter responds differently, if not always according to the nature
of the stimulus at least to its degree, it would follow that change in
the nature or degree of the environmental agencies would indirectly
engender change in the activities of the germ-plasm. Not to admit
this would be to deny to the germ-plasm, without empirical reason,
properties proven for all other living substances.

“This thought had long ago been expressed clearly, though from
a different line of reasoning, by Spencer (1865). We may state it
in another way. Tissue-cells are granted by experimental physiolo-
gists the ability of different response, or different intensity of
response, to stimuli of different kind or degree. But a tissue-cell
is a lineal descendant of a germ-cell, and receives germ-plasm
from the latter. Now since the germ-plasm has been transmitted
continuously to the tissue-cell, must not the energies of the germ-
plasms of the two be alike at least in their general response
activity? Again, a Protozoan may be considered as a cell not
exactly correspondent to a germ-cell of a Metazoan, but as some-
thing more, as a unit with properties of both a germ-cell and a
tissue-cell, for its cytoplasmic differentiations (cilia, contractile
vacuoles, cytopharynx, etc.) are comparable to the soma of a Meta-
zoan. In the case of the Protozoan Paramecium, Calkins (1904)
has shown that the reproductive activity is increased or diminished
according to the amount and kind of food stimuli. Here, then, a
Protozoan has its reproductive activities, therefore the energies of
its germ-plasm, profoundly influenced by environmental changes;
and it is primarily what we may term the germ-cell constituent of
the Protozoan that becomes influenced, that part which has to do
with reproduction of the individual. Weismann considered the

OTHER THEORIES OF SPECIES-FORMING. 399

Protozoan exactly comparable, in the sense of strict continuity of
reproduction, to the germ-cell of a Metazoan, and yet failed to
note that a Protozoan can be influenced by environmental change.

“Accordingly, an environmental change may be capable of induc-
ing change in the energies of the germ-plasm. The expression of
the energies of this substance, as viewed in temporal succession,
constitutes heredity. Therefore, the process of heredity may become
modified by a change in the environmental conditions of the germ-
plasm. And since we defined variation as a modification of heredity,
a variation could be produced by external influences acting upon
the germ-plasm, understanding by external influences influences of
the tissue-cells upon the germ-cells, or, in case the germ-cells are
not enclosed, influences of the non-living environment.”

In a recent exhaustive paper by Tower, W. L., on “Evolution in
Chrysomelid beetles of the genus Leptinotarsa,’ Publication No. 48
of the Carnegie Institution of Washington, 1907, the author, although
on the whole a strong adherent of selection as the all-important
factor in species-forming, states specifically his belief, on the basis
of extensive observation and experiment, that external factors may
and do influence the germ-plasm to the extent of compelling it to
produce variations. These variations will not be photographic re-
productions of modifications of the soma, but they will be the vari-
ations which lie at the basis of species change. In other words,
Tower holds that variations are epigenetic in their origin, although
they are manifest as congenital differences. That is, acquired
characters in the usual sense of the term are not heritable, but all
variability is nevertheless due to the influence of environment. This
paper by Tower is a distinctly valuable contribution to our knowl-
edge of heredity and species change and it is based upon a large
amount of actual close observation and experiment.

In a recent paper by Jonathan Wright, “The Origin and Heredity
of Matter,” in the St. Louis Medical Review, 1906, something of the
same attitude is taken, although the author is much more inclined
to the belief in the general heritability of acquired characteristics.
This short paper is an admirable treatment, based on a full acquaint-
anceship with the modern literature on the subject, of the problem
of heredity.

* See exposition of a number of these theories in appendix of
chapter viii of this book.

*Haacke, W., “Grundriss der Entwicklungsmechanik,” p. 289
fF. 1307.

* The following account of the scientific aspects of Luther Bur-

310 DARWINISM TO-DAY.

bank’s work, which has attracted so much attention from evolu-
tionists and the world generally, was published by Kellogg, in the
Pop. Sct., Mo., Vol. LXIX, pp. 363-374, 1906.

“Mr. Burbank has so far not formulated any new or additional
laws of species-change, nor do his observations and results justify

Solentific any such formulation, and we may rest in the belief
aspects of Bur- that he has no new fundamental laws to reveal. He
bank's work, has indeed the right to formulate, if he cares to, some

valuable and significant special conclusions touching certain already
recognised evolution factors, in particular the influence on varia-
bility of the two long-known variation-producing factors of hybridi-
sation and modification of environment. Huis reliance on the marked
increase in variability to be got after a crossing in the second and
third generations over that obvious in the first, will come as a sur-
prise to most men first getting acquainted with his work. He has
got more starts for his new things from these generations than in
any other way. He is wholly clear and convinced in his own mind as
to the inheritance of acquired characters; ‘acquired characters are
inherited or I know nothing of plant life,’ he says; and also con-
vinced that the only unit in organic nature is the individual, not
the species; that the so-called species are wholly mutable and de-
pendent for their apparent fixity solely on the length of time through
which their so-called phyletic characters have been ontogenetically
repeated. He does not agree at all with de Vries that mutations in
plants occur only at certain periodic times in the history of the
species, but rather that, if they occur at all, they do so whenever
the special stimulus derived from unusual nutrition or general
environment can be brought to bear on them. He finds in his
breeding work no prepotency of either sex as such in inheritance,
though any character or group of characters may be prepotent in
either sex. He believes that no sharp line can be drawn between the
fluctuating or so-called Darwinian variations and those less usual,
large, discontinuous ones called sports. Ordinary fluctuating varia-
tion goes on under ordinary conditions of nutrition, but with ex-
traordinary environmental conditions come about extraordinary
variation results, namely, discontinuous, sport or mutational varia-
tion. These variations are the effects of past environment also,
having remained latent until opportunity for their development
occurs. Starvation causes reversions, but reversions can also be
produced by unusually rich nutrition. New variations are developed
most often, as far as environmental influences go, by rich soil and
generally favourable conditions. So-called new qualities are usually,
if not always (the fact may sometimes not be obvious), simply
new combinations of old qualities, both latent and obvious. To get

OTHER THEORIES OF SPECIES-FORMING. git

a new and pleasing odour it may often be sufficient simply to lose
one bad element in an old odour. So one might go on for some
pages with specific conclusions or deductions reached by Burbank
on a basis of experience. But it is true that he has at his command
the knowledge of no new fundamental scientific principles to give him
advantage over us. And yet none of us has done what Burbank
has been able to do, although many of us have tried. What then
is it that Burbank brings to his work of modifying organisms
swiftly and extremely and definitely that others do not?

“To answer this it will be advisable to analyse in general terms,
at least, the various processes which either singly, or in combina-
tions of two or three, or all together, are used by Mr. Burbank in
his work. We may roughly classify these processes and means.
First, there is the importation from foreign countries, through
many correspondents, of a host of various kinds of plants, some
of economic value in their native land and some not, any of which
grown under different conditions here may prove specially vigorous
or prolific or hardy, or show other desirable changes or new quali-
ties. Among these importations are often special kinds particularly
sought for by Burbank to use in his multiple hybridisations; kinds
closely related to our native or to already cultivated races which,
despite many worthless characteristics, may possess one or more
particular, valuable ones needed to be added to a race already useful
to make it more useful. Such an addition makes a new race.

“Second, the production of variations, abundant and extreme, by
various methods, as (a) the growing under new and, usually, more
favourable environment (food supply, water, temperature, light,
space, etc.) of various wild or cultivated forms, and (b) by hybridi-
sations between forms closely related, less closely related and,
finally, as dissimilar as may be (not producing sterility), this
hybridising being often immensely complicated by multiplying
crosses, 7. ¢., the offspring from one cross being immediately crossed
with a third form, and the offspring of this with still another form,
and so on. These hybridisations are made sometimes with very
little reference to the actual useful or non-useful characteristics of
the crossed parents, with the primary intention of producing an
unsettling or instability in the heredity, of causing, as Burbank
sometimes says, ‘perturbations’ in the plants, so as to get just as
wide and as large variation as possible. Other crosses are made,
of course, in the deliberate attempt to blend, to mix, to add together,
two desirable characteristics, each possessed by only one of the
crossed forms. Some crosses are made in the attempt to extin-
guish an undesirable characteristic.

“Third, there is always immediately following the unusual produc-

312 DARWINISM TO-DAY.

tion of variations, the recognition of desirable modifications and the
intelligent and effective selection of them, 7. e., the saving of those
plants to produce seed or cuttings which show the desirable varia-
tions and the discarding of all the others. In Burbank’s gardens
the few tenderly cared for little potted plants or carefully grafted
seedlings represent the surviving fittest, and the great bonfires of
scores of thousands of uprooted others, the unfit, in this close
mimicry of Darwin and Spencer’s struggle and survival in nature.

“It 1s precisely in this double process of the recognition and selec-
tion of desirable variations that Burbank’s genius comes into
particular play. Right here he brings something to bear on his
work that few other men have been able to do. It is the extraordi-
nary keenness of perception, the delicacy of recognition of desirable
variations in their (usually) small and to most men imperceptible
beginnings. Is it a fragrance that is sought? To Burbank in a bed
of hundreds of seedling walnuts scores of the odours of the plant
kingdom are arising and mingling from the fresh green leaves, but
each, mind you, from a certain single seedling or perhaps from a
similar pair or trio. But to me or to you, until the master prover
points out two or three of the more dominant single odours. the
-impression on the olfactories is simply (or confusedly) that of one
soft elusive fragrance of fresh green leaves. Similarly Burbank
is a master at seeing, and a master at feeling. And besides he has
his own unique knowledge of correlations. Does this plum seed-
ling with its scores of leaves on its thin stem have those leaves
infinitesimally plumper, smoother or stronger, or with more even
margins and stronger petiole, or what not else, than any other
among a thousand similar childish trees? Then it is saved, for
it will bear a larger, or a sweeter, or a firmer sort of plum, or more
plums than the others. So to the bonfires with the others and to
the company of the elect with this ‘fittest’ one. Now this recogni-
tion, this knowledge of correlations in plant structure, born of the
exercise of a genius for perceiving through thirty years of oppor-
tunity for testing and perfecting it, 1s perhaps the most important
single thing which Burbank brings to his work that other men do
not (at least in such unusual degree of reliability). Enormous
industry, utter concentration and single-mindedness, deftness in
manipulation, fertility in practical resource, has Burbank—and so
have numerous other breeders and experimenters. But in his per-
ception of variability in its forming, his recognition of its possi-
bilities of outcome, and in his scientific knowledge of correlations,
a knowledge that is real, for it is one that is relied on and built on,
and is at the very foundation of his success, Burbank has an
advantage of true scientific character over his fellow workers, and

OTHER THEORIES OF SPECIES-FORMING. 313

in it he makes a genuine contribution to scientific knowledge of
plant biology, albeit this knowledge is so far only proved to be
attainable and to exist. It is not yet exposed in its details and may
never be, however unselfish be the owner of it. For the going
to oblivion of scientific data of an extent and value equivalent, I
may estimate roughly, to those now issuing from any half-dozen
experimental laboratories of variation and heredity, is the crying
regret of all evolution students acquainted with the situation. The
recently assumed relations of Mr. Burbank to the Carnegie Insti-
tution are our present chief hope for at least a lessening of this
loss.

“But let us follow our saved plum seedling. Have we now to
wait the six or seven years before a plum tree comes into bearing
to know by actual seeing and testing what new sort of plum we
have? No; and here again is one of Burbank’s contributions (not
wholly original to be sure, but original in the extent and perfection
of its development) to the scientific aspects of plant-breeding. This.
saved seedling and other similar saved ones (for from the exami-
nation of 20,000 seedlings, say, Burbank will find a few tens or
even scores in which he has faith of reward) will be taken from
their plots and grafted on to the sturdy branches of some full-grown
vigorous plum tree, so that in the next season or second next our
seedling stem will bear its flowers and fruits. Here are years saved.
Twenty, forty, sixty, different seedlings grafted on to one strong
tree (in a particular instance Burbank had 600 plum grafts on a
single tree!) ; and each seedling-stem certain to bear its own kind
of leaf and flower and fruit. For we have long known that the
scion is not materially influenced by the stock nor the stock by
the scion; that is not modified radically, although grafting sometimes.
increases or otherwise modifies the vigour of growth and the extent
of the root system of the stock.

“Tf now the fruit from our variant seedling is sufficiently desira-
ble; if it produces earlier or later, sweeter or larger, firmer or more
abundant, plums, we have a new race of plums, a ‘new creation’ to
go into that thin catalogue of results. For by simply subdividing
the wood of the new branch, 1. e., making new grafts from it, the
new plum can be perpetuated and increased at will. Simple, is it
not? No, it is anything but that in the reality of doing it; but in
the scientific aspects of it, easily understandable.

“Perhaps it may not be amiss to call attention to what must be
the familar knowledge of most of us, and that is the fact that many
(probably most) cultivated plants must be reproduced by division,
that is by cuttings, buds, or grafts, and not by seeds, in order to
grow ‘true. For a piece of a cultivated plant will grow out to be

314 DARWINISM TO-DAY.

very much like the individual it was cut from, but the seeds will
not, in most cases, reproduce faithfully the parents, but will pro-
duce a very variable lot of individuals, most of them strongly
reversionary in character. Grow peach trees from the stones of
your favourite peach and see what manner of peaches you get;
but if you want to be sure of more peaches like the ones you enjoy,
graft scions from your tree on to other trees. Indeed one of the
plant-breeder’s favourite methods of making a start for new things,
of getting the requisite beginning wealth and eccentricity of varia-
tion, is to grow seedlings, especially from cross-bred varieties.
Burbank will give you a thousand dollars for a pinch of horseradish
seed. Sugar-cane seed is needed. The amelioration of many kinds
of fruit and flowers and vegetables is checked, because in our care-
lessness we have allowed these kinds to get into that condition of
seedlessness which almost all cultivated races tend toward when
grown from cuttings. In our oranges and grape-fruit and in a score
of other fruits, the elimination of seeds is exactly one of the modifi-
cations we have bred and selected for, in order to make the fruits
less troublesome in their eating. But when we lose the seeds
entirely of a whole group of related plant kinds we may find our-
selves, as we have found ourselves actually in many cases, at the
end of our powers of amelioration of these plant sorts. Burbank
believes that the very fact that plants when grown asexually always
sooner or later lose their power to produce seeds is almost suff-
cient proof (if such proof is needed) that acquired characters are
transmitted.

“Another of Burbank’s open secrets of success is the great range
of his experimentation—nothing is too bold for him to attempt,
the chances of failure are never too great to frighten him. And
another secret is the great extent, as regards material used, of each
experiment. His beds of seedlings contain hundreds, often thou-
sands, of individuals where other men are content with hundreds.
Another element in his work is his prodigality of time. Experi-
ments begun twenty years ago are actually still under way.

“In all that I have so far written, I have purposely kept to gen-
eral statements applicable to Burbank’s work as a whole. My
readers might be more interested. perhaps, to have some illustra-
tions of the application of various processes of making new sorts
of things, some analytical account of the history of various specific
‘new creations, but considerations of space practically forbid this.
Just a few briefly described examples must suffice. More than is
‘generally imagined, perhaps, Burbank uses pure selection to get
new things. From the famous golden orange coloured California
poppy (Escholtzia) he has produced a fixed new crimson form by

OTHER THEORIES OF SPECIES-FORMING. 315

selection alone. That is, noticing, somewhere, sometime, an Escholt-
zia individual varying slightly redder, he promptly took posses-
sion of it, raised young poppies from its seeds, selected from among
them those varying in a similar direction, raised new generations
from them and so on until now he who wishes may have his
California poppies of a strange glowing crimson for the price of a
little package of seed, where formerly he was perforce content
with the golden orange. For me the golden orange suffices, but
that does not detract from my eager interest in the flower-painting
methods of Mr. Burbank. Even more striking a result is his blue
Shirley poppy, produced also solely by repeated selection from
the crimson field poppy of Europe. ‘We have long had various
shades of black and crimson and white poppies, but no shade of
blue. Out of 200,000 seedlings I found one showing a faintest trace
of sky blue and planted the seed from it, and got next year one
pretty blue one out of many thousand, and now I have one almost
pure blue.’

“But another brilliant new poppy was made in a different way.
The pollen of Papaver pilosum, a butter-coloured poppy, was put
on the pistils of the Bride, a common pure white variety of
Papaver somniferum (double), and in the progeny of this cross was
got a fire-coloured single form. The character of singleness was
common to the ancestors of both parents, the character of fire colour
in the lineage of sommniferum only, although the red of the new
form is brighter than ever before known in the somnifera series.
Both characteristics were absent (or rather latent) in both parents.
And yet the perturbing influence of the hybridisation brought to
the fore again these ancestral characters. The foliage of this fire
poppy is intermediate in type between that of the two parents.

“The history of the stoneless and seedless plum, now being
slowly developed by Burbanks, shows an interesting combination of
selection, hybridisation, and reselecting. Mr. Burbank found a
plum in a small wild plum species with only a part of a stone.
He crossed this wild species with the French prune; in the first
generation he got most individuals with whole stones, some with
parts of a stone, and even some with no stone. Through three
generations he has now carried his line by steadily selecting, and
the percentage of no-stone fruits is slowly increasing, while quality,
beauty, and productiveness are also increasing at the same time.

“The plum-cot is the result of crossing the Japanese plum and the
apricot. The plum-cot, however, has not yet become a fixed variety
and may never be, as it tends to revert to the plum and apricot
about equally, although with also a tendency to remain fixed, which
‘tendency may be made permanent.

316 DARWINISM TO-DAY.

“Most of Burbank’s plums and prunes are the result of multiple
crossings in which the Japanese plums have played an important
part. Hundreds of thousands of seedlings have been grown and
carefully worked over in the twenty years of experimenting with
plums, and single trees have been made to carry as many as 600
varying seedling grafts. The Bartlett plum, cross of the bitter
Chinese Simoni and the Delaware, itself a Simoni hybrid. has the
exact fragrance and flavour of the Bartlett pear. The Climax, a
successful shipping plum, is also a cross of the Simoni and the
Japanese triflora. This Chinese Simoni produces almost no pollen,
but few grains of it ever having been obtained. But these few
grains have enabled Burbank to revolutionise the whole plum
shipping industry. The sugar prune, which promises to supplant
the French prune in California, is a selected product of a second or
third generation variety of the Petite d’Agen, a somewhat variable
French plum.

“Next in extent probably to Burbank’s work with plums and
prunes is his Jong and successful experimentation with berries.
This has extended through twenty-five years of constant attention,
has involved the use, in hybridisations, of forty different species of
Rubus, and has resulted in the origination of a score of new com-
mercial varieties, mostly obtained through various hybridisations of
dewberries, blackberries, and raspberries. Among these may spe-
cially be mentioned the Primus, a hybrid of the western dewberry
(R. ursinus) and the Siberian raspberry (R. crategifolius), fixed
in the first generation, which ripens its main crop before most of
the standard varieties of raspberries and blackberries commence to
bloom. In this Primus berry, we have the exceptional instance of
a strong variation, due to hybridisation, breeding true from the
time of its first appearance. It usually takes about six generations
to fix a new variety, but like de Vries’s evening primrose mutations,
the Primus berry is a fixed new form from the time of its beginning.
An interesting feature of Mr. Burbank’s brief account, in his ‘New
Creations’ catalogue of 1894, of the berry experimentation, is a re-
production of a photograph showing ‘a sample pile of brush, 12
ft. wide, 14 ft. high, and 22 ft. long, containing 65,000 two- and
three-year-old seedling berry bushes (40,000 blackberry \ rasp-
berry hybrids and 25,000 Shaffer Gregg hybrids) all dug up-
with their crop of ripening berries. The photograph is introduced
to give the reader some idea of the work necessary to produce a
satisfactory new race of berries. ‘Of the 40,000 blackberry \% rasp-
berry hybrids of this kind, ““Phenomenal” is the only one now in
existence. From the other 25,000 hybrids, two dozen bushes were
reserved for further trial.’

OTHER THEORIES OF SPECIES-FORMING. 317

“An astonishing result of the hybridisation between the black
walnut, Juglans nigra, used as the pistillate parent, and the Cali-
fornia walnut, J. californica, staminate parent, are walnut trees
which grow with such an amazing vigour and rapidity that they
increase in size at least twice as fast as the combined growth of
both parents. Many tremendous growers are got in the first gen-
eration, but in the second there are included some of the most
rapidly. growing trees, perhaps, in the world. This hybrid has
clean-cut, glossy bright-green leaves from two to three feet long
with a sweet odour like that of apples, but it produces few nuts.
Curiously enough the result of hybridisation by using the pollen
of nigra on pistils of californica produces in abundance large nuts
of a quality superior to that possessed by either parent.

“The famous Shasta daisy is the result of a multiple crossing
between an American and a European species of field daisy and
then between these hybrids and a Japanese form. The fragrant
calla, known as ‘Fragrance,’ is descended from a single individual
found by Burbank while critically examining a block of Little Gem
calla seedlings. He was surprised in this examination by a fra-
grance resembing that of violets or water-lilies; as he had long
been seeking a fragrant calla, the individual giving this perfume was
carefully hunted out. No farther selecting was done; this plant
was the single ancestor of the fragrant new race.

“And so one might go on for pages, but with slight variations in
detail all these pages would tell only the same story: the stimulating
or inducing of variability by environmental influences and by hybrid-
isations; the search after, and keen recognition of, promising spe-
cial variations; the selection of the plants showing these variations;
rearing new generations from them, repeated selection, and new
hybridisations to eliminate this characteristic or introduce that,
and on until a desirable combination is found. Then the careful
fixing of this form or type by repeated selection through several
generations.

“But an end must be made of this. Let us, in a paragraph, simply
sum up the essential things in the scientific aspects of Burbank’s
work. No new revelations to science of an overturning character;
but the revelation of the possibilities of accomplishment, based on
general principles already known, by an unusual man. No new laws
of evolution, but new facts, new data, new canons for special cases.
No new principle or process to substitute for selection, but a new
proof of the possibilities of the effectiveness of the old principle.
No new categories of variations, but an illuminating demonstration
of the possibilities of stimulating variability and of the reality of
this general variability as the fundamental transforming factor.

318 DARWINISM TO-DAY.

No new evidence either to help the Darwinian factors to their death-
bed, or to strengthen their lease on life; for the ‘man’ factor in all
the selecting phenomena in Burbank’s gardens excludes all ‘natural’
factors. Here are some of Burbank’s own words, touching these
matters that scientific men are particularly interested in, in his work:

“All scientists have found that preconceived notions, dogmas,
and all personal prejudice must be set aside, listening patiently,
quietly, and reverently to the lessons one by one which mother
nature has to teach, shedding light on that which before was a
mystery, so that all who will may see and know.

““Crossing gives the raiser of new plants the only means of
uniting the best qualities of each, but just as often the worst quali-
ties of each are combined and transmitted, so that to be of any
value it must be followed by rigid and persistent selection, and in
crossing, as in budding and grafting, the affinities can only be
demonstrated by actual test.

“*All wild plants of any species are under almost identical envi-
ronments, having their energies taxed to the utmost in the fierce
struggle for existence. Any great variation under such circum-
stances is not likely to occur, and is much more likely to be stamped
out at once by its struggling competitors, unless the variation should
be of special use in competition, in which case it will survive, and
all others may be supplanted by it. Thus we see how new species
are often produced by nature, but this is not her only mode. Crosses
and hybrids are very often found growing wild where two some-
what similar species grow contiguous, and if the combination hap-
pens to be a useful one, as it often does, the new creation is
encouraged by nature; then time and environment fix it, and man
comes on the scene, perhaps ages later, and discovers it, and, not
knowing all the facts, wonders where the connecting links have
gone. It is botanically classified as a new species, which it is most
certainly.

“Tn cultivated plants the life struggle is removed, and here we
find variation almost the rule rather than the exception.

“ ‘Varieties are the product of fixed laws, never of chance, and
with a knowledge of these laws we can improve the products of
nature, by employing nature’s forces, in ameliorating old and produc-
ing new species and varieties better adapted to our necessities and
tastes. Better food, more sunshine, less arduous competition, will
of themselves induce variation in individual plants which will be
more or less transmitted to their seedlings, which, selected con-
secutively through a certain number of generations, will become
permanent. Environment here exerts an influence as in all chemical
cosmical, and celestial movements. These small increments from

OTHER THEORIES OF SPECIES-FORMING. 319

environmental forces may produce a gradual or sudden change
according to circumstances. The combustion of food liberates the
moving force, environment guides it as it does the planets.

““*When once the persistent type is broken up, old latent forces
may be liberated and types buried in the dim past reappear. This,
called atavism, is a concentration of ancestral forces—reverberating
echoes—from varieties long since passed away, exhibiting them-
selves when from some cause, for instance crossing, present forces
are in a state of antagonism, division, perturbation, or weakness.
These echoes, if collected by crossing and selection, produce com-
binations of superlative importance and value.’ ”

Pop late: 7b, ‘Uber die Bedeutung,” etc., p. 220.

® See Koken, Ernst, ‘‘Palzontologie und Descendenzlehre,” 1902.
Koken (Professor of Geology and Palzontology in the University

Orthogenetic Of Tubingen) is very explicit in the statements of his
variation in belief that the paleontological records prove the exist-
palzontology, ence of orthogenetic variation and hence evolution.
“Das Darwin’sche Prinzip der Selektion ist nicht das einzige, das.
in Betracht kommt und es scheint nicht das wichtigste zu sein.
Vielfach vermissen wir in der palzeontologischen Geschichte den
Hinweis auf ein Eingreifen des Kampfes ums Dasein und anderer-.
seits heben sich Richtungen der Entwickelung heraus. welche nicht
in Beziehung zu einem Nutzen stehen, in einigen Fallen zu einer
Schadigung der socialen Bedingungen fuhren.”

* For an account of the facts of one such case, see Kellogg, “‘Is.
There Determinate Variation,” Science, N. S., Vol. XXIV, pp. 621I-
628, 1906. In this paper the gradual but obvious change from.

Acase ofap- one dominant type of colour-pattern to another in
parent determi- the leaf-eating beetle Diabrotica soror (on the campus:
nate variation. of Stanford University, California) during the last.
ten years, is shown by statistical variation studies. It is shown
that such change is not explicable on a basis of intra-specific
selection, nor can it be interpreted as a direct ontogenic reaction -
in each succeeding generation to changing climatic conditions. The
case is believed to be an example of definitive orthogenetic:
variation.

Certain examples of presumable determinate variation have been
recorded by Henslow (‘The Origin of Species,” Natural Science,
p. 250, 1894). ‘In 1847, Prof. J. Buckman sowed seed of wild
parsnip in the garden of the Agricultural College, at Cirencester.
The seedlings began to vary, but in the same way, though in differ-.
ent degrees. By selecting seed from the best rooted plants, the
acquired ‘somatic’ characters of an enlarged root, glabrous leaves,
etc., became fixed and hereditary; and ‘The Student,’ as he called.

320 DARWINISM TO-DAY.

it, having been ‘improved’ by Messrs. Sutton & Sons, is still
regarded as ‘the best in the trade.’ This is definite variation, ac-
cording to Darwin’s definition, for those weeded out did not differ
from the selected, morphologically, except in degree, the variations
towards TABS TGet not being quite fast enough to entitle them
to survive.

“M. Carriére raised the radish of cultivation, Raphanus sativus,
L., from the wild species R. raphanistum, L., and moreover found
that the turnip-rooted form resulted from growing it in a heavy
soil, and the long-rooted one in a light soil.* Pliny records the
same fact as practised in Greece in his day, saying that the ‘male’
(turnip form) could be produced from the ‘female’ (long form), by
growing it in ‘a cloggy soil. Both forms are now, of course,
hereditary by seed.”

*? Nageli, C. von, “‘Mechanisch-physiologische Theorie der Ab-
stammungslehre,” 1884.

** Korschinsky, S., “‘Heterogenesis und Evolution,” Naturwiss.
Wochenschrift, Vol. XIV, pp. 273-278, 1890.

*? Recently, Georg Pfeffer (“Die Entwicklung,” 1895) has pro-
posed a theory of orthogenetic evolution not very different from

the much earlier Nagelian one. Pfeffer postulates as
ine inherent in living matter a capacity for change and

for self-directing this change. The principle of
change or progress he calls the conception of “‘developmental-screw”
(Entwicklungsschraube), and for directing this progress the con-
ception of “self-steering” (Selbststeuerung). Both these capacities
of individualised living stuff are something over and beyond the
mechanical and physico-chemical attributes of living matter. ‘On
the contrary,” says Pfeffer, “life consists of the capacity (more
exactly the exercise of this capacity) of consciously permitting and
consciously influencing (that is, actually producing) through
physico-chemical phenomena changes in the matter or form of the
fundamental life-stuff.”

From this curious, though keen, critical, and constructive essay,
I quote as follows:

“Der Begriff der Entwickelungsschraube deckt sich eigentlich
vollig mit dem Begriff der Selbststeuerung der lebendigen Natur;
ich halte aber mit gutem Grunde beide Ausdrticke aufrecht, weil
sie einer verschiedenen Betrachtung entspringen, namlich die
Selbststeuerung der mechanischen, die Entwickelungsschraube der
historischen, entwickelungsgeschichtlichen Betrachtungsweise; die
Selbststeuerung ist das Prinzip der Herstellung des Gleichgewichtes

* This has been corroborated by M. Languet with the carrot. Soc.
Roy. et Cent. d’Agricult., 2d ser., Vol. II, 1846-7, p. 539.

OTHER THEORIES OF SPECIES-FORMING. 32!

eines aus lebendigen Einheiten gebildeten Ganzen; die Entwickel-
ungsschraube das Prinzip der veranderten Weiterfthrung dieser
Gleichgewichtsverhaltnisse in der Zeit. Also ist, ebenso wie die
Selbststeuerung, auch die Entwickelungsschraube selbstthatig (pp.
12and 13).

“Es ist hier nicht der Ort, die physikalischen wie die Unzahl der
chemischen Eigenschaften der lebendigen Grundsubstanz zu eror-
tern; sie liegen freilich nicht auf der Hand, sind aber im Ganzen
ziemlich leicht herzuleiten als das allen lebendigen protoplasmati-
schen Substanzen Gemeinsame. Es fallt aber Niemandem ein, bez.
sollte Niemandem einfallen, die physikalischen und chemischen
Eigenschaften der lebendigen Substanz als Lebens-Eigenschaften zu
betrachten; vielmehr besteht das Leben in der Fahigkeit (bez. der
Austibung der Fahigkeit), die durch chemisch-physikalische
Vorgange an dem Stoff oder der Form-Auspragung der Grund-
substanz bewirkten Veranderungen bewusst zu erleiden und bewusst
zu beeinflussen (bez. hervor zu bringen). Es hat also jeder kor-
perliche Vorgang der lebendigen Substanz seinen von ihm untrenn-
baren Bewusstseinsvorgang; oder anders ausgedruckt: jeder Vor-
gang an lebendigen Wesen hat einen in chemisch-physikalische und
einen anderen in Bewusstseins-Verhaltnisse zerlegbaren Anteil.
Beide sind Gegenstande wissenschaftlicher Betrachtung, dagegen
entzieht sich die Art und Weise des Zusammenhanges zwischen
beiden unserm Anschauungsvermogen, liegt also ausserhalb der
naturwissenschaftlichen Betrachtung und ist damit als gegeben
hinzunehmen”’ (p. 17).

A recent proposal of an orthogenetic theory of the general
character of Nageli’s is that set out in O. F. Cook’s ‘Aspects of
Kinetic Evolution,” Proc. Wash. Acad. Sct., Vol. VIII, pp. 197-403,
1907.

** Eimer, Th., “Die Entstehung der Arten auf Grund von Verer-
bung erworbener Eigenschaften nach den Gesetzen organischen
Wachsens,” I, 1888; trans. into English, as “Organic
Evolution,” 1889; “Artbildung und Verwandschaft
bei den Schmetterlingen,” I, 1889, II, 1895; “Ortho-
genesis bei Schmetterlinge” (Part II of ‘Die Entstehung der
Arten’”), 1898; ‘‘Orthogenesis,’ 3 Internat. Congress Zool., 1895;
trans. in English as “On Orthogenesis and the Impotence of Natural
Selection in Species-Formation,” 1898. This address, and Eimer’s
other writings as well, are sadly marred by intemperate polemic
and the indulgence of personal rancor. He deems himself and his
views unfairly overlooked by biologists and seems to hold Weismann
personally responsible for this. Apart from these unfortunate
digressions his papers are extremely suggestive and logically and

Eimer’s theory
of orthogenesis,

322 DARWINISM TO-DAY.

keenly composed. I believe that Eimer’s work and theories should
have more attention from students of evolution then they now get.

** Dean, Bashford. ‘Evolution in a Determinate Line, as Illus-
trated by the Egg-Cases of Chimeroid Fishes,” Biol. Bull., Vol.

Apparent deter- VII, pp. 105-112, 1904. In this paper the author
minate evolution. expresses his belief that the conditions existing in the
curious inter-related adaptations between eggs and egg-cases of the
shatk-like fish, Chimera, can be explained only on the basis of
determinate or orthogenetic modifications, in which modifications
neither natural selection nor the Lamarckian factors of use and
disuse can have played any part. The capsule or egg-case, although
“only indirectly connected with the egg, 1.e., as a secretion formed
by the parent after the mechanism of heredity has already been
established in the egg, nevertheless foresees with startling exact-
ness the size and shape of the young fish when many months hence
it comes to hatch out, and it provides a series of progressive multi-
plications adapted to the physical needs of the young. It is evident,
accordingly, that if natural selection be adduced to explain the
present phenomena it encounters difficulties more numerous and
complex than in usual instances. In the latter cases selection con-
cerns itself with variations which affect the progeny directly; but
in the present case variations must have occurred in the lines both
of the progeny and, indirectly, of its far less indifferent capsule-
forming capabilities—with result that a succession of closely corre-
lated stages in variation must have coincided in both distinct con-
ceptions.”

* Plate, L., “Uber die Bedeutung,” etc., p. 190 ff.

*® Rosa, Daniel. ‘“La Riduzione Progressiva della Variabilita 1
suoi Rapporti coll’ Estinzione e coll’ Origine della Specie,” 1899.
Author believes that in animal life there is a gradual progressive
reduction of variation (or modification) necessitated by the well-
known fact that highly specialised forms have distinctly fewer lines
of modification, 7. e. specialisation, left open to them than general-
ised forms; and that all groups of animals are of the nature of
series of more and more specialised forms. He bases this belief, as
far as facts go, on the well-known cases of the dying out of spe-
cialised species (Irish stag) and specialised groups (Cretaceous
reptiles), and on the alleged facts (which the author devotes many
pages to trying to show) that all present-day principal groups of
animals are related to each other solely by derivation from com-
mon very old and generalised ancestors. If there is less modifica-
tion possible, then there occurs actually less and less variability, and
the actually occurring variations will be only along certain lines,
1. e. there will be in this limited variability an actual basis for ortho-

OTHER THEORIES OF SPECIES-FORMING, = 323

genesis. On the double basis of progressively less variation and of
the thus produced orthogenesis the author sees a factor in phylogeny
(organic evolution) which works, to some degree, independently of
natural selection or of Lamarckian factors. Rosa thinks he has
thus contributed to biology one of the always sought-for “unknown
factors in evolution.”

17 Tn an interesting paper by Snodgrass, ‘“The Relation of the Food
to the Size and Shape of the Bill in the Galapagos Genus Geospiza,”

Snodgrass’s Auk, Vol. XIX, pp. 367-381, 1902, detailing the ex-
observations on amination of the stomach contents of over 200 indi-
billsof Gala-~ = viduals, representing 13 species and sub-species (taken
pagos birds. from several of the Galapagos Islands) of the peculiar
Galapagos Fringillid genus, Geospiza, remarkable for the great
differences in size and shape of bill characterising the various
species and sub-species, the author states that all the “evidence
seems to be in favour of the general conclusion that there is no
correlation between the food and the size and shape of the bill.”
The following five propositions were established: (1) The same
species at different localities may feed on different seeds; (2)
different species at the same locality may feed on the same kinds
of seeds; (3) different species at different localities may feed on
the same kinds of seeds; (4) different species at the same or at
different localities may feed on different seeds; and (5) birds
with small bills eat only small seeds; birds with large bills eat both
small and large seeds. The seeds taken from the stomachs varied
in size from seeds of 1 cubic millimetre up to those 15 mm. long
by 10 mm. thick. The bill of the different species and sub-species
of Geospiza, varies from that of G. scandens scandens, 13 mm.
long by 7 mm. high at base, to that of G. pachyrhyncha, 17 mm.
long by 20 mm. high at base.

** Eimer, Th., “Orthogenesis der Schmetterlinge,”’ 1897.

** Cope, E. D., “The Method of Creation of Organic Types,”
Proc. Amer. Phil. Soc., December, 1871.

*° Cope, E. D., “The Energy of Life Evolution,” Pop. Sci. Mo.,
Vol. XXVII, pp. 789-800, October, 1885: “Primary Factors of
Organic Evolution,” 1896.

** “Paleontologists, as a rule—and Prof. Cope is one of them,—
are so profoundly impressed by the adaptive nature of the evolu-

Cope’s belief | tionary process and by the definitiveness of its direc-
in orthogenetic tion, that they cannot regard the restraining or
evolution. selective action of the environment as enough to keep
the breed true. They are so accustomed to seeing mutation after
mutation, generation after generation, developing in apparent obe-.
dience to obvious physico-chemical or mechanical conditions, that

324 DARWINISM TO-DAY.

they incline to regard these conditions as causes. And if it be
suggested to them that the results they see may have been achieved
by the selection of adaptive variations from among a number of
promiscuous variations that are not adaptive, they ask why it is
that they do not find evidence of these numerous known adaptive
variations in the organs, when one would suppose that, on any
hypothesis, except that of definite variation, such forms must have
been the more abundant of the two. It is useless to reply to them
that the known adaptive variations in each generation were killed off
when young, and so, even if fossilised, are practically undistinguish-
able; because they will reply with abundant proof that the adaptive
characters chiefly appear in the adult stages of the organism, possibly
only in its senile stages, and so are incapable of coming under
the action of natural selection during the early undifferentiated
stages. How the conversation might continue does not much
matter, for it 1s obvious that it has reached a point beyond which all
must be speculation. The facts on which the paleontologist relies,
the facts that Prof. Cope adduces with such wealth of knowl-
edge, are strong presumptive evidence in favour of his second
thesis, but they are not proof.” (Bather, F. A., Natural Science,
Vol. X, pp. 40-41, 1897.)

Prof. Scott, another American paleontologist, discusses the
question of variation in an interesting paper in the American Journal
of Science, Vol. XLVIII, pp. 335-374. 1894. The great point made
by Prof. Scott is the clear distinction between individual and
phylogenetic variation. Individual variation is irregular and not
fixed, while ‘phylogenetic variation,” or mutation (in the sense of
* Waagen) which is distinguished from individual variation, not
by any character of quantity or quality, but by pursuing a deter-
minate direction and thus, under control of natural selection, leading
to the formation of new species. ‘‘Remembering that the signifi-
cant fact in the history of a group is not so much the character of
its variations at any one stage, as the gradually shifting positions
successively occupied by the normal or centre of stability, we find
that any mammalian series at all complete, such as that of the
horses, is remarkably continuous, and that the progress of discovery
is steadily filling up what few gaps remain. So closely do successive
stages follow upon one another that it is sometimes extremely

* The term “mutation” was first used in biology, probably, by
Waagen, 1869, in a paper on the phylogeny of an ammonite. In
this first use of the word its meaning was a change or modification
accomplished during a considerable historic period. Indeed, it had
much the meaning of evolution or descent as we use these terms
nowadays.

OTHER THEORIES OF SPECIES-FORMING. = 325

difficult to arrange them all in order and to distinguish clearly
those members which belong in the main line of descent, and those
which represent incipient branches. Some phylogenies actually
suffer from an embarrassment of riches.”

?? Whitman, C. O., ‘The Problem of the Origin of Species,” Pro-
ceedings of Congress of Arts and Science, Universal Exposition, St.

Whitman's Louis, Vol. V, pp. 41-58, 1906. In this paper Whit-
belief in deter- man takes strong ground for orthogenesis and recites
minate variation. jn detail a number of interesting facts touching the
evolution of pattern in pigeons to illustrate his belief. Touching
the criticism of orthogenesis, that it involves a teleologic element
in its make-up, Whitman says (p. 5): “I take exception here only
to the implication that a definite variation-tendency must be con-
sidered to be teleologic because it is not ‘orderless.’ I venture to
assert that variation is sometimes orderly, and at other times rather
disorderly, and that the one is just as free from teleology as the
other. In our aversion to the old teleology so effectually banished
from science by Darwin we should not forget that the world is
full of order, the inorganic no less than the organic. Indeed, what
is the whole development of an organism if not strictly and marvel-
lously orderly? Is not every stage, from the primordial germ on-
ward, and the whole sequence of stages, rigidly orthogenetic? If
variations are deviations in the directions of the developmental
processes, what wonder is there if in some directions there is less
resistance to variation than in others? What wonder if the organ-
ism is so balanced as to permit of both unifarious and multifarious
variations? If a developmental process may run on throughout
life (e. g., the life-long multiplication of the surface-pores of the
lateral-line system in Amia), what wonder if we find the whole
species gravitating slowly in one or a few directions? And if
we find large groups of species, all affected by a light variation,
moving in the same general direction, are we compelled to regard
such ‘a definite variation-tendency’ as teleological, and hence out
of the pale of science? If a designer sets limits to variation in
order to reach a definite end, the direction of events is teleological ;
but if organisation and the laws of development exclude some
lines of variation and favour others, there is certainly nothing super-
natural in this, and nothing which is incompatible with natural
selection. Natural selection may enter at any stage of ortho-
genetic variation, preserve and modify. in various directions the
results over which it may have had no previous control.”

** Cunningham, an English neo-Lamarckian, expresses (‘Origin
of Species Among Flatfishes,” Natural Science, Vol. VI, p. 2309,
1895) his belief in orthogenesis as follows:

326 ~ DARWINISM TO-DAY.

“The only general view, as it seems to me, which can be held

concerning the structural diversity of the animal kingdom, is to
regard it as resultant of two more or less opposing

Cunningham = general tendencies. On the one hand, there is uni-

and orthogenesis. : é Ly
versal evidence of a tendency to definite variation, or

growth in different directions, leading to manifold variety of regu-
lar definite symmetrical forms. This tendency can only be regarded
as internal to the organism, as connected with a tendency to growth
and multiplication inherent in organic units. On the other hand,
there is the molding, limiting, constructing action of the external
forces of the environment resulting in more or less complete adap-
tation. Whatever be the process of adaptation, whether Darwinian
selection or Lamarckian modification, adaptive structural combina-
tions are mechanisms each working with the particular result which
is important to the feeding, living, and breeding of the organism.
Whatever the causes of non-adaptive variation, the resulting struct-
ural features are the regular genetic forms and characters which the
multitude of different organic forms present in such marvellous
diversity. No one who, like Weismann, ignores everything except
adaptation, or who, like Bateson, regards the study of adaptations
as barren and profitless, can hope to produce a consistent and com-
prehensive theory of organic evolution.”

** Delage, Yves, “L’Hérédité,” 2d ed. p. 849, and others, 1903.

°° Taeckel, O., “‘Uber verschiedene Wege phylogenetischer Ent-
wicklung,” 1902.

CHAPTER XI.

OTHER THEORIES OF SPECIES-FORMING AND
DESCENT (CONTINUED): ALTERNATIVE
THEORIES (CONTINUED).

Heterogenesis—Under the name heterogenesis we have
to consider a theory of species-forming which is more popu-
larly and widely known under another name, viz., the muta-
tions theory. This theory is commonly associated with the
name of de Vries, the Amsterdam botanist. But this gen-
eral conception of species-forming on a basis of the occur-
rence of occasional, sudden, fixed, and often considerable
changes or variations in the offspring of a plant or animal,
isa ‘conception not of course new with de Vries, but one
variously expressed by numerous biologists from Dar-
win’s time on, especially by von Kolliker, Galton, Dall,
Bateson, Emery, Scott, and Korschinsky. It is, however,
chiefly due to the patient, persistent, well-planned, and ex-
tensive experiments and observations of de Vries that this
theory of species-forming by heterogenesis, or.as called by
de Vries, by mutations, has recently received so much re-
newed attention. With the observations of de Vries on the
breeding of certain plant species, notably certain GEnotheras
(evening primroses), there have been much associated in
recent popular scientific literature accounts of the ear-
lier observations of Gregor Mendel,” an Augustinian monk,
who recorded, in 1865, in an obscure journal, some very
valuable observations and logical conclusions concerning the
phenomena of heredity in certain other plants (especially
garden peas). Reference should also be made, in this con-

327

328 DARWINISM TO-DAY.

nection, to observations and experiments carried on nearly
simultaneously with those of de Vries by Correns* and
Tschermak.? As a matter of fact the data on which de
Vries bases his theory of species-forming by heterogenesis
are, in part, nearly identical with those obtained by Mendel,
Tschermak, and Correns, which, however, is concerned
primarily with explaining the “laws” of heredity.

The meaning of heterogenesis in connection with species-
forming and descent is essentially this: whereas by the
Darwinian theory species are transformed slowly and by
slight changes in at first one or two or a few and only
later in more parts, and all new species are derived from the
old ones (which usually disappear as the new ones appear)
by the gradual selection of the advantageous cnes among the
regular slight, fluctuating, individual variations (known
commonly as Darwinian variations and which mostly occur
according to the law of error), by the theory of hetero-
genesis new species appear suddenly, not by a selective
choosing among the slight fluctuating Darwinian variations,
but independently of selection, and largely independently of
the so-called Darwinian variations, by the appearance in
fixed definitive form of several to many slight to consider-
able variations, which give the new species definite char-
acteristics differentiating it often in many particulars from
the old species, which differentiating characteristics are fully
and faithfully transmitted to the succeeding generations of
individuals derived from this suddenly born new species.

In some theories or views of heterogenesis the suddenly
appearing new variations—and none of these theories gives

a satisfactory explanation of the cause of these

Bra aie sudden variations—which give rise to new
species, are those large, sometimes monstrous,

variations known as “‘sports,” “monsters,” etc.; or, in Bate-
son’s words, are “discontinuous variations,” 7. ¢., considerable
variations not connectéd bya continuous: series of gradations.

OTHER THEORIES OF SPECIES-FORMING. 329

with the parent type of the variable organ or individual.
Darwinians have always been interested in such variations,
for if they do occur in any considerable numbers they might
offer a possible solution of that difficulty in the selection
theory of explaining the origin of new structures and the
needed degree of size and development sufficient to make
these beginnings useful and hence available as handles for
natural selection. But it has long been recognised that such
sports or discontinuous variations are too few and occur too
rarely to furnish the basis for a comprehensive theory of
species-forming. Like the extremes of individuals in the
series of fluctuating variations, their characters would be
lost or swamped by crossing. Darwin himself made as full
a list of such sports as any post-Darwinian writer, ex-
cepting Bateson, has been able to do, and he recognised
the fact that certain species, or races at least, of domesticated
animals and cultivated plants undoubtedly had their begin-
nings in these sports. His examples of such discontinuous
or saltatory evolution as the Ancon and Mauchamp sheep,
the Paraguay cattle,* etc., are the classic examples in ani-
mal evolution, and to this day nearly the only ones! Bate-
son” has, to be sure, gathered together in his “Materials.
for the Study of Variation” a much larger list of sports or
discontinuous variations than Darwin included in his knowl-
edge (it should be borne in mind in referring to Bateson’s
list that several, probably, indeed, many of his alleged ex-
amples are cases of teratogenic regeneration)—but he has
been able to add almost no new examples of the origin of
a new species from such discontinuous variations. A few
cases are known of the inheritance through a number of
generations of suddenly appearing sports or discontinuous
variations in human beings (cases of polydactyly, etc.) and
cats. (Kennel’s stump-tailed cat, which produced in six
litters four stump-tailed, twelve tailless, and twelve normal
young, is an example of several similar cases which have.

330 DARWINISM TO-DAY.

been recorded.) Species-forming by sports and discon-
tinuous variations is obviously no theory to presume to
offer itself as a species-forming substitute for natural selec-
tion. But the de Vriesian mutations theory, the most
recent development of the heterogenesis conception, has
rehabilitated this conception to such an extent that a number
of biologists see in it an actually satisfactory substitute for
the natural selection theory. Before explaining the theory
of de Vries let us first note two or three other prior formula-
tions of theories of heterogenesis, one at least being nearly
identical with that of de Vries.

In 1864 the great zoologist von Kolliker,* in a paper under
the title “Uber die darwinische SchSpfungstheorie,” took
positive ground against the adequacy oractuality
of natural selection as a species-forming factor,
and proposed a theory of “heterogene Erzeu-
gung” (heterogenesis) which he formulated, however, only
in most general terms. He said that “under the influence
of a general law of development (evolution) organisms
bring forth other kinds differing from them out of the
germs produced by them.” He included in his general theory
of heterogenesis a basic plan of progressive evolution.
Such a conception has in it too much autogenic orthogenesis ;
it is too redolent of teleology for present-day biology. The

Von Kolliker’s
suggestion.

variations, too, which are to serve as beginnings of new
species are those too rare ones which we have referred to
as sports and discontinuous variations.
The American naturalist, Dall,” in a paper written in
1877, expresses his conviction that sudden changes of
species-forming character do occur, and as-
_ Dall’sbelief cribes such changes “to the action of the
in sudden spe- , ;
cies-change, law of development, which finds expression
in the paradox that the same species may
belong to different genera.” That sudden leaps may be
due to the gradual accumulation of minute differences he

OTHER THEORIES OF SPECIES-FORMING. 331

exemplifies as follows: “In a sloping gutter of a paved
street not too cleanly swept every one will notice on a sudden
shower how small particles of earth and other materials
will sometimes act as a dam, producing a puddle which,
relieved by partial draining, may for a time remain in
statu quo. A time comes, however, when the gradually
accumulated pressure suddenly sweeps the dam before it
for a short distance, until another similar one is formed, the
pool again appears for a time to remain unchanged, and
so on indefinitely. Now the modern idea of a species may be
stated to be a greater or lesser number of similar individual
organisms in which for the time being the majority of
characters are in a condition of more or less stable equi-
librium, and which have the power to transmit these char-
acters to their progeny with a tendency to maintain this
equilibrium. This tendency may be, in some cases, sufficiently
strong to resist for a considerable period the changes which
a gradual modification of the environment may tend to bring
about. When the latter has reached a pitch which renders
the resistance no longer effectual, it is conceivable that a
sudden change may take place in the arrangement of the
constitution of the organism, adapting it once more to its
surroundings, when the tendency to equilibrium may reassert
itself in the minor characteristics, and they may, as it were,
crystallise once more in a form not dissimilar in generic
type. If among a certain assemblage of individuals con-
stituting a species, the tendency to maintain the specific
equilibrium be (as it should be a priori) transmitted to the
progeny in different degrees of intensity, a gradual separa-
tion might take place between those with a stronger
tendency to equilibrium and those with less. Here natural
selection would come in. Those yielding as above to the
pressure of the environment would necessarily become better
adapted to it (or perish) and with their changed generic
structure might be able to persist. On the other hand, those

ORE

332 DARWINISM TO-DAY.

with the broader base, so to speak, with the inherited
tendency to remain unshaken by the modifications of the
environment, may be conceived as through this tendency
to be and to remain less injuriously affected by adverse
circumstances, and consequently might still endure. In
short, natural selection in the one case would find its ful-
crum in the tendency to easy adjustment of characters; and
in the other case in the inherited persistency in equilibrium
rendering its possessor more or less indifferent to the in-
jurious elements of the environment. The intermediate
individuals by the hypothesis would be those least-fitted to
persist in any case and hence liable to be rapidly eliminated.
Then we should have parallel series of species in two or even
more genera existing simultaneously.”

Francis Galton, the great student of heredity and, in most
of his belief a thorough Darwinian, nevertheless held it to be

probable that evolution might proceed not only

Galton’s belief Hy minute steps but that decisive sudden changes
in discontinuous
steps. of the type may occur. “That the steps may

be small and that they must be small are very

different views; it is only to the latter that I object, and
only when the indefinite word ‘small’ is used in the sense of
‘barely discernible’ or as small compared with such large
sports as are known to have been the origin of new races.” *
And his familiar analogy of organic stability to that of the
polygon * with unequal sides, whose stability or r fixity de-
presses well the basic ides in sc helerapeness or rnitaien -
small but definitive and fairly stable changes. Galton also
believed in the stability or fixity of sports; not that all trans-
mit their character to their young but that many do and thus
give rise to new types.

Emery,’” in his suggestive paper called “Gedanken zur
Descendenz- und Vererbungstheorie,” expresses his belief
in the importance in species-forming of what he calls “pr

OTHER THEORIES OF SPECIES-FORMING. 333

mary variations,” which are large and sudden as contrasted
With “secondary variations,’ which are the usual small,
Emery’ fluctuating or so-called Darwinian variations.
ery’s the- ; ’ :
ory ofprimary Emery bases his belief on the few cases like
variations.” the Ancon sheep and the inherited six-fingered-
ness of men, and also on an argument drawn from the dif-
ficulty of explaining by the natural selection theory various
existing conditions such as sexual polymorphism, and numer-
ous cases of extremely complex structural and physiological
specialisation. But there is little that is convincing in
Emery’s presentation.
A later exponent of heterogenesis of a different kind, and
a more sharply-spoken antagonist of the selection theory,
Eetuchincky's much more nearly anticipates de Vries’s muta-
theory of hetero- tion theory. Indeed this biologist, the Russian
geneets botanist Korschinsky, in his championship of
heterogenesis goes much beyond de Vries in his denial of the
influence of selection in species-forming and descent. De
Vries, as we shall see, admits natural selection to be a factor,
and perhaps a large one in the determination of descent, of
organic evolution, but holds it to be wholly a restraining and
cutting-back factor, not at all a formative one. Korschinsky |
says plainly that the struggle for existence and selection
have either no influence in species-forming and descent, or,
if any, a hindering and antagonising influence, a retarding
and nullifying influence. Korschinsky has published his
theory in three papers, one a large work in Russian which I
have not seen, the others shorter papers ** in German which
are of the nature of vorlaiifige Mitteilungen. In these
papers he formulates clearly and positively a theory of
heterogenesis or species-forming by “mutations” and attacks
sharply and positively the natural selection theory. A con-
cise statement of his theory and at the same time of his
position with regard to the selection theory is given by.
him in a table of two columns in which the contrast between

the two theories is graphically shown.

DARWINISM TO-DAY.

I translate here this

“parallel columns” statement in full:

ACCORDING TO THE TRANSMUTA-
TION THEORY.

1. To all organisms there be-
longs a capacity for variation
which is called into play partly
through inner, partly through
outer causes, through use and
disuse, etc. This capacity for
variation regularly finds its ex-
pression in the appearance of
slight and unnoticeable individ-
ual differences.

2. As a result of this strug-
gle for existence and selection,
those individual variations
which prove themselves useful
become fixed and accumulated,
while the non-useful ones dis-
appear. All characteristics and
peculiarities of a species must,
as a result of a prolonged selec-
tion, stand in harmony with the
outer conditions, and be useful
to the organism.

3. Through prolonged selec-
tion and accumulation of char-
acteristics all species undergo
a persistent change, whereby
they are gradually transformed
into new species without, how-
ever, sacrificing their normal
physiological relations.

4. This process can take place
everywhere and under all cir-
cumstances. The harder the
outer conditions and the sharp-
er the struggle for existence,
the more energetically selection
works, and therewith the quick-

ACCORDING TO THE THEORY OF
HETEROGENESIS.

1. To all organisms there be-
longs a capacity for variation,
which is a fundamental inner
peculiarity independent of outer
conditions, and which remains
usually in latent condition, re-
tained by heredity, but which
now and then finds its expres-
sion in sudden changes.

2. These sudden changes can,
under favourable conditions, be
the beginnings of persistent
races. These new characteris-
tics, having appeared independ-
ently of outer conditions, are
sometimes useful to the organ-
ism, but they may also stand in
no harmony with outer condi-
tions.

3. All once-formed species re-
main unchanged, although new
forms occasionally split off from
them by heterogenesis. Such
newly-arisen forms have, as the
result of a disturbed heredity, a
deranged constitution, which re-
veals itself in a lessened fertility
and often in a generally weak-
ened condition of the organism.
The new forms, becoming con-
stant races, gradually recover
their constitution.

4. The origin of new forms
can, however, occur only under
favourable conditions of exist-
ence for the species, and the
more favourable these condi-
tions, that is, the less severe
the struggle for existence, the

OTHER THEORIES OF SPECIES-FORMING.

er the development of new

forms.

5. The chief requisite for evo-
lution is, therefore, the struggle
for existence and the selection
which results from it.

6. If there were no struggle
for existence, no selection, no
survival of the strongest, there
would be no evolution and no
specialisation, for adapted spe-
cies would have no advantage
over unadapted ones, and as a
result of crossing with the lat-
ter, they would sacrifice their
useful characteristics.

7. The so-called advance in
nature or the perfecting of or-
ganisms, is nothing else than a
more complex, more complete
adaptation to outer conditions,
and it is reached in a purely
mechanical way through selec-
tion and the accumulation of
characteristics useful under the
existent outer conditions.

335

more energetically can evolution
go on. New forms do not arise
under hard external conditions,
or if any do, they go quickly to
ground.

5. The struggle for existence,
and the selection that goes hand
in hand with it, constitute a fac-
tor which limits new forms and
hinders further variation and is,
therefore, in no way favourable
to the origin of new forms. It
is a factor inimical to evolution.

6. If there were no struggle
for existence, there would be -no
killing out of newly arising or al-
ready arisen forms. The world
of organisms could then grow to
a mighty tree, whose branches
could all persist in blossoming
condition, and the most aberrant,
now isolated, species would be
connected with all others through
intermediate forms.

7. The adaptation which
comes to exist through the
struggle for existence is not at
all identical with an advance, for
higher, more specialised (voll-
kommenere) forms are by no
means alwavs better adapted to
outer conditions than the lower
ones. One cannot explain the
evolution of organisms in a
purely mechanical way. In or-
der to explain the origin of
higher forms out of lower it is
necessary to admit a_ special
tendency, in organisms, for ad-
vance, which is nearly related
to, or identical with the tend-
ency to vary, and which com-
pels organisms toward perfect-
ness as far as external conditions
allow.

The theory of heterogenesis as formulated by Korschinsky
(and also as held by de Vries, as we shall see) 1s not neces-

336 DARWINISM TO-DAY.

sarily a theory of sudden large changes or variations, al-
though it is of sudden and fixed ones. It is not based on
any belief that sports or large variations are any more
numerous, nor of any more worth as the beginnings of new
species, than now generally recognised, but it assumes
sudden radical changes in the organism which, if not visibly
large as regards obvious quantitative conditions, are large or
at least comprehensive as regards qualitative conditions.
The mutation or variation assumed by the theory of hetero-
genesis affects many organs and parts, structurally and
physiologically ; it produces a radical change throughout the
organism. And this change is the result of an influence
wholly intrinsic, inherent, and has no reference to external
conditions, except in that the stimulus for it may come partly
or chiefly from specially favourable conditions of nutrition.
This change is at once definitive and fixed: it is transmitted
unimpaired to the offspring of the organism showing the
mutation, only the capacity for the production of offspring,
1. ¢., the reproductive fertility, is often weakened.

Korschinsky’s theory and declarations are not based on
any very large amount of personal experimentation and
observation—at least his references to new facts are few and
meagre. He gives a short list of old and more or less
familiar together with a few new examples of heterogenesis
but he does not lend the theory of heterogenesis very much
in the way of authority, except in so far as the evidently
positive and clear conviction on the part of a biologist of
experience and reputable standing of the necessity and truth
of such a theory is authority. Korschinsky’s conviction is
probably based on much observation and experience besides
that which he definitely catalogued, but what is needed to
carry conviction to others is direct reference to proved, and
where possible verifiable, facts of observation and experi-
ment.

The supplying of this demand, to a degree which will

OTHER THEORIES OF SPECIES-FORMING. 337

appear to various people insufficient or sufficient according
to their respective ideas of what is needed in

De Vriesand the way of fact material for the satisfactory
the mutations ; peo we ; .
theory. founding of a theory, it is the special vir-

tue of de Vries to have attempted on behalf
of heterogenesis.

De Vries ** introduces his now classic two-volume pres-
entation of his views on evolution and species-forming
(“Die Mutationstheorie,” 1901-1903) with the following
paragraph:

“Als Mutationstheorie bezeichne ich den Satz, dass die
Eigenschaften der Organismen aus scharf von einander
unterschiedenen Einheiten aufgebaut sind. Diese Einheiten
konnen zu Gruppen verbunden sein, und in verwandten
Arten kehren dieselben Einheiten und Gruppen wieder.
Ubergange, wie sie uns die ausseren Formen der Pflanzen
und Thiere so zahlreich darbieten, giebt es aber zwischen
diesen Einheiten ebensowenig, wie zwischen den Molekulen
der Chemie.” And again in the first paragraph of the
preface to his book ‘Species and Varieties” ** (an edited
transcription of his American lectures on species-forming,
delivered in California in 1904) he says: “. . . but the
way in which one species originates from another has not
been adequately explained. The current belief assumes that
species are slowly changed into new types. In contradic-
tion to this conception the theory of mutation assumes that
new species and varieties are produced from existing forms
by sudden leaps. The parent-type itself remains unchanged
throughout this process, and may repeatedly give birth to
new forms. These may arise simultaneously and in groups,
or separately at more or less widely distributed periods.”

Obviously there is no ambiguity here as to the relation
of species-forming by mutation to species-forming by
gradual modification through selection or fluctuating varia-
tions. In the words of de Vries: “Species have not arisen

238 DARWINISM TO-DAY.

through gradual selection continued for hundreds or thou-
sands of years, but by jumps (stufenweise) through sudden,
though small, transformations. In contrast with variations
which are changes in a linear direction the transformations
to be called mutations constitute divergence in new directions.
They take place, so far as experience goes, without definite
direction.” ** And even if transition forms exist between
the species produced by mutations, they are no evidence
against the mutations, “for,” says de Vries, “the transitions
do not appear before the new species, at most only simul-
taneously with this, and generally only after this is already
in existence. The transitions are therefore no intermediates
or preparations for the appearance of the new forms. The
origin takes place, not through them, but wholly independ-
ently of them.” *°
Too often de Vries’s theory is said not to be alternative
with Darwin’s, but auxiliary to it. As regards the forma-
tion of new species, the two theories are directly
De Vries's in opposition. But as regards the general
nai course of organic evolution (which is another

opposition to
Darwin's as con- matter) the mutations theory is not in contra-

rise diction to the theory of descent through

selection. De Vries himself says: “Notwith-
standing all these apparently unsurmountable difficulties,
Darwin discovered the great principle which rules the evolu-
tion of organisms. It is the principle of natural selection.
It is the sifting out of all organisms of minor worth through
the struggle for life. It is only a sieve, and not a force of
nature, no direct cause of improvement, as many of Dar-
win’s adversaries, and unfortunately many of his followers
also, have so often asserted. It is only a sieve, which de-
cides which is to live, and what is to die. But evolutionary
lines are of great length, and the evolution of a flower or
of an insectivorous plant.is a way with many side-paths. It
is the sieve that keeps evolution on the main line, killing

OTHER THEORIES OF SPECIES-FORMING. 339

all or nearly all that try to go in other directions. By this
means natural selection is the one directing cause of the
broad lines of evolution.” **

While de Vries admits that recorded mutations are few;
“mutations under observation are as yet very rare; enough
to indicate the possible and most probable ways but no
more;” *” yet he strongly maintains that there is no scientific
proof of the origin of species in any other way than by
mutation and that there is such proof of their actual muta-
tional origin. He says: “I intend to give a review of the
facts obtained from plants which go to prove the assertion
that species and varieties have originated by mutation and
are, at present, not known to originate in another way.”

But in any consideration of de Vries’s work and theories,
one must have clearly in mind the distinctive meaning
which de Vries attaches to the word species. However
little biologists agree on any absolute definition of species,
the term nevertheless is consistently used to refer to differ-
entiated organic types between any two of which there is
considerable obvious describable difference, either quali-
tative or quantitative. If two types of such obvious differ-
ence in one or several characteristics (usually external or
at least externally noticeable differences are the ones used)
are connected by a series of connecting gradatory forms
existing either in the same territory or in other regions, the
two forms are not referred to as distinct species but as
varieties ; at least the form at one end of the series is called
a variety of the form at the other end. But de Vries’s
species and varieties are of different stuff. Specific dis-
tinctions with him are based on differences in aggregation
of the elementary units, the Einheiten, that go to compose
the specific types. “Species is a word,’ says de Vries,
“which always has had a double meaning. One of them is
the systematic species, which is the unit of our system.
But these units are not at all indivisible. Long ago Lin-

340 DARWINISM TO-DAY.

nzus knew them to be compound ideas in a great number
of instances, and increasing knowledge has shown that the
same rule prevails in other instances. To-day the vast ma-
jority of the old systematic species are known to consist of
minor units. These minor entities are called varieties in sys-
tematic works. However, there are many objections to this
usage. First, the term variety is applied in horticulture and
agriculture to things so widely divergent as to convey no
clear idea at all. Secondly, the subdivisions of species are
by no means all of the same nature, and the systematic
varieties include units the real value of which is widely
different in different cases. Some of these varieties are in
reality as good as species, and have been ‘elevated,’ as it is
called, by some writers, to this rank. This conception of the
elementary species would be quite justifiable, and would at
once get rid of all difficulties, were it not for one practical
obstacle. The number of the species in all genera would be
doubled and tripled, and as these numbers are already
cumbersome in many cases, the distinction of the native
species of any given country would lose most of its charm
and interest.

“In order to meet this difficulty we must recognise two
sorts of species. The systematic species are the practical
units of the systematists and florists, and all friends of wild
nature should do their utmost to preserve them as Linnzeus
has proposed them. These units, however, are not really
existing entities; they have as little claim to be regarded
as such as the genera and families have. The real units
are the elementary species; their limits often apparently
overlap and can only in rare cases be determined on the
sole ground of field-observations. Pedigree-culture is the
method required and any form which remains constant and
distinct from its allies in the garden is to be considered as
an elementary species.” *”

With regard to varieties de Vries has the following to

OTHER THEORIES OF SPECIES-FORMING. 34!

say: “Linneus himself knew that in some cases all sub-
divisions of a species are of equal rank, together constituting
the group called species. No one of them outranks the
others; it is not a species with varieties, but a group con-
sisting only of varieties. A closer inquiry into the cases
treated in this manner by the great master of systematic
science shows that here his varieties were exactly what we
now call’elementary species.

“In other cases the varieties are of a derivative nature.
The species constitutes a type that is pure in a race which
ordinarily is still growing somewhere, though in some cases
it may have died out. From this type the varieties are
derived, and the way of this derivation is usually quite
manifest to the botanist. It is ordinarily by the disappear-
ance of some superficial character that a variety is dis-
tinguished from its species, as by the lack of colour in the
flowers, of hairs on stems and foliage, of the spines and
thorns, etc. Such varieties are, strictly speaking, not to be
treated in the same way as elementary species, though they
often are. We shall designate them by the term of ‘retro-
grade varieties,’ which clearly indicates the nature of their
relationship to the species from which they are assumed to
have sprung. In order to lay more stress on the contrast
between elementary species and retrograde varieties, it
should be stated at once, that the first are considered to
have originated from their parent-form in a progressive
way. They have succeeded in attaining something quite
new for themselves, while retrograde varieties have only
thrown off some peculiarity, previously acquired by their
ancestors.” *°

With regard to the facts and general evidence ** on which

The facts at © VtIeS bases his beliefs and theory a few
basis of de ‘words, too few, I regret, must suffice. Like
Vries's theory. Darwin, de Vries only came to the full pub-
lication of his theory after many years of assiduous obser-

342 - DARWINISM TO-DAY.

vation, of persistent compilation of other men’s observing,
and careful weighing and consideration of the data in
hand. In de Vries’s case too there was added a large
amount of experimental testing of his conclusions. This
experimental study of the species-forming problem de
Vries and his followers rather seem to claim as a distinct-
ively new part of the basis for the mutations theory, but as
a matter of fact Darwin himself, in much less degree per-
haps, and in somewhat different manner, appealed to experi-
ment to test many of his conclusions. The actual forming
of new species by selection could not be experimentally
tested or proven by Darwin. Whether biologists are ready
to accept de Vries’s pedigree-culture work and results as
of the same nature of rigid experimental test and proof as
there exists in experimentation in chemistry and _ static
physics (for that is the claim for the new “experimental
method” in biology) remains, perhaps, a moot point. De
Vries’s general statement of the character and the amount
of the evidence on which he rests his belief in the formation
of species by mutation is contained in the following para-
graphs from his book “Species and Varieties” (p. 22).
“Mutations are occurring from time to time in the wild
state as well as in horticulture and agriculture. A-selec-
tion of the most interesting instances will be given later.
But in all such cases the experimental proof is wanting.
The observations, as a rule, only began when the mutation
made its appearance. A more or less vague remembrance
about the previous state of the plants in question might be
available, though even this is generally absent. But on
doubtful points concerning possible crosses or possible intro-
duction of foreign strains, mere recollection is insufficient.
The fact of the mutation may be very probable, but the full
proof is, of course, wanting. Such is the case with the
mutative origin of Xanthium commune Wootom from New
Mexico and of Cnothera biennis cruciata from Holland.

>. **

OTHER THEORIES OF SPECIES-FORMING. 343

The same doubt exists as to the origin of the Capsella
Heegeri of Solms-Laubach, and of the oldest recorded muta-
tion, that of Chelidonium laciniatum in Heidelberg about
1600.” | ~

Next, after introducing the necessity of experimental
proof and explaining how one must go to work to acquire
such proof he refers to his own well-known work with
Lamarck’s evening primrose as follows (pp. 26-29) :

“Complying with these conditions, the origin of species
may be seen as easily as any other phenomenon. It is only

necessary to have a plant in a mutable condi-

The work with tion. Not all species are in such a state at
Lamarck’s even-
ing primrose, Present, and therefore I have begun by ascer-

taining which were stable and which were not.

These attempts, of course, had to be made in the experi-
mental garden, and large quantities of seed had to be pro-
cured and sown. Cultivated plants, of course, had only a
small chance to exhibit new qualities, as they have been so
strictly controlled during so many years. Moreover their
purity of origin is in many cases doubtful. Among the wild
plants only those could be expected to reward the investi-
gator which were of easy cultivation. For this reason |
have limited myself to the trial of wild plants of Holland,
and have had the good fortune to find among them at least
one species in a state of mutability. It was not really a
native plant, but one probably introduced from America
or at least belonging to an American genus. It was the
great evening-primrose or the primrose of Lamarck. A
strain of this beautiful species is growing on an abandoned
field in the vicinity of Hilversum, at a short distance from
Amsterdam. Here it has escaped from a park, and multi-
plied. In doing so it has produced, and is still producing,
quite a number of new types, some of which may be con-
sidered as retrograde varieties, while others evidently are
of the nature of progressive elementary species.

344 DARWINISM TO-DAY.

“This interesting plant has afforded me the means of ob-
serving directly how new species originate, and of studying
the laws of these changes. My researches have followed a
double line of inquiry. On one side, I have limited myself
to direct field observations, and to trials of seed, collected
from the wild plants in their native locality. Obviously the
mutations are decided within the seed, and the culture of
young plants from them had no other aim than that of
ascertaining what had occurred in the field. But then the
many chances of destruction that threaten young plants in a
wild state could be avoided in the garden, where environ-
mental factors can be controlled.

“My second line of inquiry was an experimental repetition
of the phenomena which were only partly discerned at the
native locality. It was not my aim to intrude into the
process, nor to try to bring out new features. My only ob-
ject was to submit to the precepts just given concerning
pure treatment, individual seed-gathering, exclusion of
crosses, and accurate recording of all the facts. The result
has been a pedigree which now permits of stating the rela-
tion between all the descendants of my original introduced
plant. This pedigree at once exhibits the laws followed by
the mutating species. The main fact is, that it does not
change itself gradually, but remains unaffected during all
succeeding generations. It only throws off new forms,
which are sharply contrasted with the parent, and which
are from the very beginning as perfect and as constant, as
narrowly defined, and as pure of type as might be expected
of any species.

“These new species are not produced once or in single
individuals, but yearly and in large numbers. The whole
phenomenon conveys the idea of a close group of mutations,
all belonging to one single condition of mutability. Of
course this mutable state must have had a beginning, as it
must sometime come to an end. It is to be considered as a

OTHER THEORIES OF SPECIES-FORMING. 345

period within the life-time of the species, and probably it is
only a small part of it.”

The following paragraphs and diagram quoted from
Morgan * give an admirably concise statement of the actual
details of the primrose mutations observed by de Vries.

“We may now proceed to examine the evidence from
which de Vries has been led to the general conclusions given

in the preceding pages. De Vries found at
Morgan’s : :
account ofde Fiilversum, near Amsterdam, a locality where
Meee experi a number of plants of the evening primrose,
, CEnothera lamarckiana, grow in large numbers.
This plant is an American form [native to the Southern
United States] that has been imported into Europe. It
often escapes from cultivation, as is the case at Hilversum,
where for ten years it has been growing wild. Its rapid
increase in numbers in the course of a few years may be one
of the causes that have led to the appearance of a mutation
period. The escaped plants showed fluctuating variations
in nearly all of their organs. They also had produced a
number of abnormal forms. Some of the plants came to
maturity in one year, others in two, or in rare cases in
thivee, years.

“A year after the first finding of these plants de Vries
observed two well-characterised forms, which he at once
recognised as new elementary species. One of these was
O. brevistylis, which occurred only as female plants. The
other new species was a smooth-leafed form with a more
beautiful foliage than O. lamarckiana. This is O. levtfolia.
It was found that both of these new forms bred true from
self-fertilised seeds. At first only a few specimens were
found, each form in a particular part of the field, which
looks as though each might have come from the seeds of a
single plant.

“These two new forms, as well as the common O. la-
marckiana, were collected, and from these plants there have

346 DARWINISM TO-DAY.

arisen the three groups or families of elementary species that
de Vries has studied. In his garden other new forms also
arose from those that had been brought under cultivation.
The largest group and the most important one is that from
the original O. lamarckiana form. The accompanying table

CENOTHERA LAMARCKIANA.,

ELEMENTARY SPECIES.

GENERATION.

Gigas
Albida.
Oblongata.
Rubriner-

vis

ana.
Nannella.
Scintillans.

| Lamarcki-
Lata.

is)
~
Lan

ee © Daan te 8 Gener. 1,700
1899 ~-
annual
a ME eer egrie 7 Gener. 9 O 3,000 II
1898 - /
annual
WE os eeniea ee 6 Gener. II 29 4. Efe = 5
1897 o> yi J
annual
Vi adeeuesed ey 5 Gener. a5 135° 20 3,000 “46. S427 @
1896 ' ~- 4
annual
EN 2s euendees 4 Gener, I 45 1x76 S$ 34,000 *60.. 94 I
1895 a a J
annual
Rit as ane ek 3 Gener. tr 10,000 4 4
1890-91 ‘ ~ /
biennial
EO ER see mee 2 Gener. 15,000 5 5
1888-89 \ np /
biennial
aoe ys arr Fee 1 Gener. 9
1886-87
biennial

tu
~
fe)

shows the mutations that arose between 1887 and 1899 from
these plants. The seeds were selected in each case from
self-fertilised plants of the /amarckiana form, so that the
new plants appearing in each horizontal line are the
descendants in each generation of /amarckiana parents. It
will be observed that the species, O. oblongata, appeared
again and again in considerable numbers, and the same is

OTHER THEORIES OF SPECIES-FORMING. 347

true for several of the other forms also. Only the two
species, O. gigas and QO. scintillans, appeared very rarely.

“Thus de Vries had, in his seven generations, about fifty
thousand plants, and about eight hundred of these were
mutations. When the flowers of the new forms were arti-
ficially fertilised with pollen from the flowers on the same
plant, or of the same kind of plant, they gave rise to forms
like themselves, thus showing that they are true elementary
species.* It is also a point of some interest to observe that
all these forms differed from each other in a large number
of particulars.

“Only one form, O. scintillans, that appeared eight times,
is not constant as are the other species. When self-
fertilised its seeds produce always three other forms, O.
scintillans, O. oblongata, and O. lamarckiana. It differs in
this respect from all the other elementary species, which
mutate not more than once in ten thousand individuals.

“From the seeds of one of the new forms, O. levifolia, col-
lected in the field, plants were reared, some of which were
O. lamarckiana and others O. levifolia. They were allowed
to grow together, and their descendants gave rise to the
same forms found in the /amarckiana family, described
above, namely, O. lata, elliptica, nannella, rubrinervis, and
also two new species, O. spatulata and leptocarpa.

“In the /ata family only female flowers are produced, and,
therefore, in order to obtain seeds they were fertilised with
pollen from other species. Here also appeared some of the
new species already mentioned, namely, albida, nannella,
lata, oblongata, rubrinervis, and also two new species, ellip-
tica and subovata.

“De Vries also watched the field from which the original
_ forms were obtained, and found there many of the new
species that appeared under cultivation. These were found,

* O. lata is always female, and cannot, therefore, be self-fertilised.
When crossed with O. lamarckiana there is produced fifteen to twenty
per cent. of pure Jata individuals.

348 DARWINISM TO-DAY.

however, only as weak young plants that rarely flowered.
Five of the new forms were seen either in the Hilversum
field, or else raised from seeds that had been collected there.
These facts show that the new species are not due to culti-
vation, and that they arise year after year from the seeds
of the parent form, O. lamarckiana.”
Since the publication of de Vries’s theory and the data

and considerations on which it is based (these considera-

tions including an unusually keen and effective

Attitude of a pce i

naturalists to- Criticism of the Darwinian factors of species-
ward the muta- forming) a great deal of discussion of the
tions theory. : ;

theory has been indulged in. On the whole
the theory has been warmly welcomed as the most promis-
ing way yet presented ** out of the difficulties into which
biologists had fallen in their attempts to explain satisfactorily
the phenomena of the origin of species through Darwinian
selection. And especially has been welcomed the fruitful idea
of unit species characters, and of the indivisibility and the
distinctness of such characters in inheritance. But with all
the interest aroused by de Vries’s presentation of his theory,
and with all the eager scrutiny of species and records of
species-appearing an output of new evidence amazingly
small (when one stops to consider the publicity gained for
the theory itself and its obvious need of more confirmatory
data of observation and experiment) has resulted. Even
though the answer may be that experiment takes time, the
lack of new observational evidence of the occurrence of
mutations,’* and of the origin of new species through muta-
tions in nature, is significant. It is my belief that a reaction
against the curiously swift and widespread partial to com-
plete acceptance of the mutation theory as the sufficient ‘“‘way
out” of our troubles to explain the origin of new species will
soon occur. (See notes 24, 25, and 26, the appendix of this
chapter, for references to certain recent criticisms of the
mutation theory.)

OTHER THEORIES OF SPECIES-FORMING. 349

In closing this confessedly inadequate consideration of
the important work and theorising of de Vries we should
not fail to note that the mutations theory is
Weeroe. in strong contrast to any theory of species-
trasted with forming based on Lamarckian principles in that
Lamarckism. : : : ;
the newly appearing differences in organisms
leading to the establishment of new species are purely con-
genital: that is, the mutations arise in one or both of the
sex cells and only later appear in the adult organism. There
is no question of the transference to the germ-cells of
changes induced in the soma by use or disuse or functional
stimulus in such a way as to result in the photographic
reappearance of these changes in the offspring. Mutations
are true congenital or blastogenic variations. “The muta-
tion theory,” well says Conklin,”’ “is a theory of the evolu-
tion of organisms through the evolution of their germ-cells.”

The mutations theory is also in sharp contrast to the
theory of species-forming by geographical isolation (see

chapter ix). According to de Vries many dis-

Mutations : : ee :

theory contrasted tinct species (de Vriesian elementary species)
eee can and do exist side by side in the same range.

In fact they “are found to be heaped up in the
centre of their area of distribution, but are more scattered
at the periphery.” ** Now according to Wagner, Gulick,
and Jordan two closely allied species, 7. ¢., stock and off-
shoot, are found practically never to inhabit the same range,
except in those cases where a migration of one type into
the territory of the other has taken place after the differ-
entiation has been effected (by previous segregation).

It would carry us into too extended a discussion to at-
tempt to sum up here the pertinent criticism that has been
directed against the mutations theory. As already indicated,
there is plenty of it and of distinctly non-negligible char-
acter. But just now it seems to me sufficient simply to call
attention to the extreme meagreness in quantity of the real

350 DARWINISM TO-DAY.

scientific evidence for the theory as a theory capable of ex-
plaining species-forming as a whole. There is probably no
gainsaying the actuality of the occurrence of certain muta-
tions (in de Vries’s sense) nor of their establishment of
certain apparently fixed new organic types (de Vries’s
elementary species of CEnothera). But this is very far
from accepting the mutations theory as a sufficient causal
explanation of the origin of the hundreds of thousands of
species of animals and plants that are now or were formerly
existent.

As for the help that the establishment of the mutations
theory would give those biologists who reject the natural

1 ; : 29
Morgan's sufn- selection theory of species-forming, Morgan

mation ofthe writes as follows, summing up the advantages

advantages of
am sonra ae of the theory:

theory, “rt. Since the mutations appear fully formed
from the beginning, there is no difficulty in accounting for
the incipient stages in the development of an organ, and

since the organ may persist, even when it has no value to

the race, it may become further developed by later muta-

tions and may come to have finally an important relation to

the life of the individual.

“2. The new mutations may appear in large numbers, and
of the different kinds those will persist that can get a foot-
hold. On account of the large number of times that the
same mutations appear, the danger of becoming swamped
through crossing with the original form will be lessened
in proportion to the number of new individuals that arise.

“2. If the time of reaching maturity in the new form is
different from that in the parent forms, then the new species
will be kept from crossing with the parent form, and since
this new character will be present from the beginning, the
new form will have much better chances of surviving than
if a difference in time of reaching maturity had to be gradu-
ally acquired.

‘OTHER THEORIES OF SPECIES-FORMING. 351

“4. The new species that appear may be in some cases
already adapted to live in a different environment from that
occupied by the parent form; and if so, it will be isolated
from the beginning, which will be an advantage in avoiding
the bad effects of intercrossing.

“cs. It is well known that the differences between related
species consist largely in differences of unimportant organs,
and this is in harmony with the mutation theory, but one
of the real difficulties of the selection theory.

“6. Useless or even slightly injurious characters may
appear as mutations, and if they do not seriously affect the
perpetuation of the race, they may persist.”

Finally, the attention of students especially may be called
to Bateson’s interesting suggestion that mutations mav be

Beeontanae: simply pure Mendelian recessives appearing
gestion that mu- atter a crossing. It would take us too far
ret oa: afield to attempt to explain here to readers.
cessives, unacquainted with the Mendelian principles
of inheritance just how Bateson’s suggestion has a certain
plausibility. It must suffice to say that Mendel, and after
him a considerable number of present-day students of
heredity, have shown that after a crossing between two
individuals sharply contrasting in regard to some particular
character, as colour of hair, all the offspring of the first
generation may agree in showing but one of the two parental
colours (the dominant), but that if these first generation
offspring are bred to each other, or to similarly produced in-
dividuals, the members of the second generation will split
up as regards the character in question, some showing one
of the grand-parental hair colours, and the rest showing the:
other one. Now breeding likes together, it would be shown
in third generation groups that one of these colours, and,
namely, that one called the recessive, which did not appear:
at all in the first generation, will always henceforth breed
true while the other colour may or may not breed true (de--

352 DARWINISM TO-DAY.

pending on whether in making the matings pure dominants
or cross-bred dominants happen to be used). Thus the
sudden appearance in the second generation of the latent or
recessive characteristic, and its breeding true, are occur-
rences which might readily be interpreted as the appearance
of a mutation or true-breeding sport by an observer unac-
quainted with the ancestry of the individuals under his eye.

Alternative Theories to Explain Secondary Sexual Char-
acters.—Before closing this discussion of theories which
have been proposed as substitutes for the Darwinian selec-
tion theories to explain the actual conditions in the organic
world as we see it to-day, and as we know it to have been
in past ages, we should mention, at least, the few attempts
to formulate a substitute explanation for the existence of
secondary sexual characters. The discrediting of the sexual
selection theory as such an explanation is certainly nearly
complete. But it is interesting to note how lame and uncon-
vincing are the proposed substitute explanations.

The first, and most appealing one, is the explanation that
the extra plumes, wattles, horns, the unusual display of

bright colours, etc., of the males are simply the

Extra growths manifestations of an extra growth-force or
the result of ‘ oe ; :
extravigour, Vigour exhibited by the male in the breeding

season. The female also may be endowed with
extra growth-vigour at this time, but it goes, in her case, to
the formation of ova, to the storing up of food in or around
the egg cells. The songs, the dances, the violent play and
antics of the males common to many species of birds, insects,
spiders, etc., are also attributed to this special or sexual
vigour.

Now while such secondary sexual characters as colour,
plumes, wattles, etc., might perhaps well enough seem to
be the outcome of an extra growth-vigour, what about such
special male characters as the stridulating organs of male
katydids and crickets, and other similar complex, highly

OTHER THEORIES OF SPECIES-FORMING. 353

perfected, adaptive structures? A male cricket has the
veins at the base of one wing-cover curiously and com-
plexly modified in course and in superficial structure, while
the veins of the other wing-cover are also modified in a way
differing from but exactly correlated with the venation of
the first wing, the whole specialisation resulting in a com-
bination of file, scraper, and vibrating membrane to form the
effective musical instrument of the insect. Can such an
adaptive structural modification be conceived to be a sudden
bursting forth or result of superabundant growth-force?
And many of the secondary sexual characters are of this
class of ¢omplex adaptive specialisations. The growth-
force explanation can, at best, explain but few of the various
categories of sexual dimorphism. Some explanation more
directive in its character is needed for these others.
Even more restricted in its application, and less con-
vincing in the assumptions at its very base, is the curious
replacement theory of Emery.’” This investi-
Emery’s theory ' ‘ ,
of the origin of ator believes that sexual selection can explain
oe but few if any cases of sexual dimorphism, and
would explain these other cases largely by the
sudden appearance (mutation or sport) of a second form
of male or female, the persistence for a while of the two
forms side by side, as now exemplified by numerous dimor-
phic or polymorphic (or di- or polychromatic) species, and
then the gradual or sudden dying out (killing out by selec-
tion?) of the older original form (the one resembling the
other sex), thus leaving the once dimorphic sex represented
only by the newer aberrant form. While such an explana-
tion may possibly explain a few cases of extreme sexual
dimorphism or dichromatism, it certainly will not do for
the many cases of secondary sexual difference constituted
by the existence in one sex of some one or few particular
adaptive specialisations for music-making, scent-producing,
or weapon-forming, not possessed by the other sex.

354 DARWINISM TO-DAY.

Cunningham ** (and also at about the same time Wigles-
worth) in 1898 suggested, on a neo-Lamarckian basis, that
. secondary sexual characters were due to the
peas are stimulation of parts through use or external
secondary sexual violence or irritation. Cunningham would ex-
characters, ‘ : ‘ a
plain all adaptations as derived from variations
actually induced by responses or reactions to the environ-
ment. His theory of the origin of secondary sexual char-
acters would simply be the explanation of the adaptive dif-
ferences between two individuals of a species on the same
basis as the explanation of the adaptive differences between
individuals of different species. His argument is summed
up as follows: “Selection assumes the occurrence of varia-
tions; the variations must either be similarly indefinite and
promiscuous in all cases, or they must be different in differ-
ent cases—that is, in different species, different sexes, dif-
ferent stages of life. If they are different in different cases,
then selection is a very unimportant matter, for the chief
questions are evidently what are the differences and what
made them differ. To deny that the variations have always
been different in different cases is to deny the most evident
facts; such denial might be possible when we consider only
the difference between species, but it is impossible when
we study the differences between the sexes in the same
species and between different stages in the same individual.
In all cases the variations correspond to differences in habits
and mode of life, and in many cases are of the same kind
as the changes known to be produced in the individual by
special stimulation or special activity of organs; this is true
of many and probably of all cases of adaptation. The gen-
eral conclusion is that adaptation is not produced indirectly
by the selection from indefinite variations, but directly by the
influence of stimulation in modifying the growth of the
parts or organs of the body.”
Wallace * has suggested that the differences in color-

rec

OTHER THEORIES OF SPECIES-FORMING. = 355°

ation between males and females are due largely to the
necessity of the better protection of the young
wataoe's producing and (in the case of birds and mam-
suggestion, ‘ :
mals) young protecting and caring for female,
and hence the acquirement on her part of a dull incon-
spicuous protective colour-pattern. Wallace’s large ac-
quaintanceship with birds and butterflies enables him to
illustrate his theory by many apparently confirmatory ex-
amples, but as soon as one stops to consider the matter
thoughtfully the impossibility of the general or even wide
application of this explanation of secondary sexual char-
acters is at once apparent. It is necessarily limited to one
single category of sexual differences.

Barrett-Hamilton ** has noted that both sexes of the sal-
mon (Onchorhynchus) become markedly discoloured during
the spawning season. The discoloration is accompanied by
overgrowth or hypertrophy, especially of the jaws. “I can-
not believe,” he says, “that this is of an esthetic nature, since
these phenomena terminate in the death of the fish. They
seem to be, in fact, merely the outward symptoms of what,
as I have persuaded myself from personal observation in
Kamschatka, is a pathological condition accompanying, and
perhaps resulting from, the growth of the ova and milt.
I regard the whole metamorphosis as a purely excretory
phenomenon resulting from the upsetting of the metab-
olism due to the concentration of the whole vital force
on the effort to produce the greatest possible amount of
spawn.

“May not such a state of things be invoked to explain the
nuptial changes of our own salmon so strangely assumed
before and lost after the breeding-season? Is it not possible
that in the phenomena displayed by the spawning Oncho-
rhynchus we may have a clue to the origin of the hitherto
inexplicable temporary and permanent sexual characters
of the vertebrates and even of some invertebrates, of which

356 DARWINISM TO-DAY.

it may be that the origin has been primarily excretory and
only secondarily protective or zsthetic ?”

The plain truth is that the satisfactory, all-explaining ex-
planation of secondary sexual characters and sexual dimor-
phism as a whole is yet to be formulated.

APPENDIX.

1 At some time between 1855 and 18605, Gregor Johann Mendel,
an Augustinian monk in the small Austrian village of Brunn, car-

Mendel and ried on pedigree cultures of peas and some other
his work. plants in the gardens of his cloister. From this work
he derived data that he read, together with his interpretation of
their significance, before meetings of the Natural History Society
of Briinn, and which, in the same year of their reading, 1865, were
published under the title “Experiments in Plant-hybridisation,” in
the Abhandlungen (Vol. IV.) of the society. Mendel was the son
of a peasant and had been educated in Augustinian foundations and
ordained priest. For two or three years he studied physics and
natural science in Vienna, and refers to himself as a student of
Kollar. He became Abbot of his cloister, and was for a time
president of the Brtinn Natural History Society. Such are the
essential details of the education and situation of the man whose
name will undoubtedly live forever in the annals of biological
science. For the observations, experiments, and conclusions of
Mendel on inheritance have taken their place already as matters of
fundamental importance in the study of heredity. It would take
us too far afield even to outline Mendel’s work and derived “princi-
ples of heredity,” but the interested reader can find an admirable
exposition and discussion of them (together with translations of
Mendel’s own papers) in Bateson’s ‘““Mendel’s Principles of Hered-
ity,’ 1902.

For an excellent exposition of Mendel’s work and other similar
work by botanists, see Lotsy, J. P., ‘““Vorlesungen tuber Descendenz-
theorien,” Vol. I, chap. viii, 1906.

Cuenot, in L’Année Biologique, Vol. VII. for 1902, pp. 58-77,
gives an excellent review of the work of Mendel, de Vries, Cor-
rens, and Tschermak; and a bibliography, relating to the so-called
Mendelian laws of the principles of heredity.

Bateson, in ““Progressus rei Botannicae,” Vol. I, pp. 368-468, 1907,
gives a complete abstract of the nature of the work and its results
which has been done on the Mendelian problem from the time of

OTHER THEORIES OF SPECIES-FORMING. o57

Mendel to the present. The bibliography in connection with this
paper is practically complete up to the date of its making.

? Correns, C. G., “Uber Levkoyen-Bastarde, zur Kenntniss der
Grenzen der Mendel’schen Regeln,” Botan. Centralbl., LXXXIV,

References to P- 97, 1900; “Uber Bastarde zwischen Rassen von
recent workon Zea Mays,” Ber. Deut. Bot. Ges., XIX, 211 (1901) ;
Mendelism. “Bastarde zwischen Maisrassen, Bibliotheca Bota-
nica,’ Heft 53, 1001; “Uber Bastardirungs-Versuche mit Mirabilis-
Sippen,” Ber. Deut. Bot. Ges., XX, 594-608, 1903.

*T. E. Tschermak, “Uber kiinstliche Kreuzung bei Pisum sati-
vum,” Zeitschr. f. d. Landwirthsch. Versuchswesen, III, 465-555,
1900; “Weitere Beitrage iiber Verschiedenswerthigkeit der
Merkmale bei Kreuzung von Erbsen und Bohnen,” ibid. IV, 641 ff.,
1901; “Uber Ztchtung neuer Getreiderassen mittelst kunstlicher
Kreuzung,” ibid.. IV, 1902. ‘Die Theorie der Kryptomerie und des
Kryptohybridismus,” Beihefte z. Bot. Centralbl., XVI, 25 pp., 1903;
“Weitere Kreuzungsstudien an Erbsen,” Zeitschrift f. d. Landwirth-
Versuchswesen in Oesterr., 106 pp., 1904.

*See Darwin, “Animals and Plants Under Domestication,” Vol.
I, chap. ili, p. 104. “In some few instances new breeds [of sheep]

Darwih ov have suddenly originated; thus in 1791 a ram-lamb was
race origin from born in Massachusetts, having short crooked legs and
sports. a long back, like a turnspit dog. From this one lamb

the otter, or ancon, a semi-monstrous breed, was raised; as these
sheep could not leap over the fences it was thought that they would
be valuable; but they have been supplanted by merinos, and thus
exterminated. The sheep are remarkable from transmitting their
character so truly that Colonel Humphreys never heard of ‘but one
questionable case’ of an ancon ram and ewe not producing ancon
offspring. When they are crossed with other breeds the offspring,
with rare exceptions, instead of being intermediate in character,
perfectly resemble either parent; even one of twins has resembled
one parent and the second the other. Lastly, ‘the ancons have been
observed to keep together, separating themselves from the rest of
the flock when put into enclosures with other sheep.’

“A more interesting case has been recorded in the Report of
the Juries for the Great Exhibition (1851), namely, the produc-
tion of a merino ram-lamb on the Mauchamp farm, in 1828, which
was remarkable for its long, smooth, straight, and silky wool. By
the year 1833 M. Graux had raised rams enough to serve his whole
flock, and after a few more years he was able to sell stock of his
new breed. So peculiar and valuable is the wool, that it sells at
25 per cent. above the best merino wool: even the fleeces of half-
bred animals are valuable, and are known in France as the

358 DARWINISM TO-DAY.

‘Mauchamp-merino. It is interesting, as showing how generally
any marked deviation of structure is accompanied by other devia-
tions, that the first ram and his immediate offspring were of small
size, with large heads, long necks, narrow chests, and long flanks,
but these blemishes were removed by judicious crosses and selec-
tion. The long smooth wool was also correlated with smooth horns;
and as horns and hair are homologous structures, we can under-
stand the meaning of this correlation. If the Mauchamp and ancon
breeds had originated a century or two ago, we should have no
record of their birth; and many a naturalist would no doubt have
insisted, especially in the case of the Mauchamp race, that they had
each descended from, or been crossed with, some unknown aborig-
inal form.”

The Paraguay cattle are a hornless race which is composed of
the descendants of a hornless bull which was born in Paraguay in
1770.

A recent interesting case wholly parallel with those just recorded,
is that of the Polled Herefords originating in 1889 in Kansas, U.
S. A. (see Guthrie, W. W., “History of Polled Herefords,” in Proc.
Am. Breeders’ Assoc., Vol. Il, pp. 93-95, 1906).

“In the fall of 1889, W. W. Guthrie. Sr., of Atchison, Kansas,
now deceased, discovered among the calves that had been weaned
at his ranch in Chase County, Kansas, one with Here-

A recent ex- : ; :
ample of race ford markings which was perfectly polled. In his
origin from a herd were purebred Shorthorn as well as purebred

sport in cattle Hereford cows. Two purebred Hereford bulls were

at the head of the herd. This calf was the product of a three-
quarter Hereford and one-quarter Shorthorn cow by one of the
two purebred Hereford bulls, Grateful 3d, No. 8,001, and Treasurer,
No. 10,585. Discovery, as the calf was subsequently named, was a
well-formed animal, with a good loin, and well-developed hind-
quarters, and had the Hereford colour and markings, with body
more on the type of the Shorthorn. At three years of age he
weighed, without special feeding, 1,986 lbs.

“It then occurred to Mr. Guthrie that by using this animal he
might in time establish a herd of polled Herefords, and that the
experiment was at least worth trying. Shortly afterwards, he
happened to meet on the train Chancellor Snow, of the Kansas
State University, on his way to lecture before the Atchison High
School on evolution, and during their several hours conversation
discussed with him the proposition of animal architecture. The
Chancellor agreed that the proposition of establishing a polled
Hereford herd was one worth considering, and Mr. Guthrie deter-
mined to carry out his ideas along this line.

ert

OTHER THEORIES OF SPECIES-FORMING. 359

“When Discovery matured it was found that his calves from
horned cows were all hornless. In 1893, a two-year-old bull and
six heifers were selected and brought to Atchison County, where
the experiment was carried on under the personal supervision of
Mr. Guthrie and with very encouraging results.

“On October 31, 1898, Mr. Guthrie purchased at the Kansas City
Scott & Whitmann sale four purebred Hereford heifers. The calves
from these horned heifers by a descendant of Discovery were found
to be in every instance polled, only two showing scurs, scarcely
noticeable, and loose in the skin. A number of purebred Hereford
heifers were later obtained from the Funkhouser herd, and still
later others from the Armour herd, and equally good results were
obtained. ;

“Eight head of polled Herefords were exhibited by Mr. Guthrie
at the Omaha Exposition, and, while these animals did not present
the finished appearance of modern show cattle, not having been
forced from date of birth, they attracted such attention that articles
on the herd were published in the newspapers and periodicals
throughout this country, and even in such far-away lands as Aus-
tralia and New Zealand. :

“The desirability of Herefords without horns, the one objection
which Hereford breeders had been willing to admit, becoming appa-
rent, other Hereford breeders began to take notice of an occasional
polled calf, freaks of nature as they were considered, appearing
in their herds, and Soon a brisk demand for polled bulls developed,
animals being shipped as far north as South Dakota, and Wiscon-
sin, and as far south as Texas. Breeders in many instances have
reported that in their horned herds, after several years’ breeding.
not a single calf had come with horns, and only occasionally would
slight scurs, loose in the skin, appear.” ...

“In December, 1904, four head of polled Herefords from West
Virginia were exhibited at the International Live Stock Show at
Chicago in connection with horned Herefords, and during the past
season a larger number from the same State were exhibited through-
out the eastern circuit of fairs. At the American Royal Cattle
Show at Kansas City, last October, seven head from the original
herd were exhibited. As a result of these exhibits, many horned
Hereford breeders are now turning their attention to the subject of
breeding Herefords without horns, and so great has become the
demand for animals with which to start polled herds that at the
last meet of the National Polled Hereford Breeders’ Association it
was found that the members were unable to supply enough young
bulls to meet the demand. .

“Quite a number of purebred Hereford calves, termed ‘freaks’

360 DARWINISM TO-DAY.

or ‘sports,’ have been dropped in this country, and some have been
kept. The President of the National Polled Hereford Breeders’
Association has a perfectly polled cow, the produce of one of his
purebred horned Hereford cows by a purebred horned Hereford
bull, and has lately purchased a purebred polled Hereford bull.
The original herd now contains two polled males and a number of
polled females, descended direct from purebred Herefords. The
above animals are registered in the American Hereford Record.

“During a trip through England several years ago, Mr. Guthrie
made inquiry among Hereford breeders and found that, while an
occasional polled animal had been calved, they were considered as.
freaks of nature by the owners and butchered.”

°> Bateson, Wm., ‘Materials for the Study of Variation,” 1894.

° K6lliker, A. von, “Uber die Darwin’sche Schdpfungstheorie,”
Zeitsch. f. wiss. Zool., Vol. XIV, pp. 174-186, 1864.

Dall, Wil, 1s77.

® Galton, Francis, ‘“Natural Inheritance,” p. 32, 1889.

® Galton, Francis, loc. cit. p. 27, “‘The distinction between primary

Galton's dis) and subordinate positions of stability will be made
cussion of spe- clearer by the help of Fig. 1, which is drawn from a
cific stability. model I made. The model has more sides, but Fig.
1 suffices for illustration. It is a polygonal slab that can be made to
stand on any one of its edges when set upon a level table, and is

B A Cc B D Cc
FIG. I

intended to illustrate the meaning of primary and _ subordinate
stability in organic structures, although the conditions of these must
be far more complex than anything we have wits to imagine. The
model and the organic structure have the cardinal fact in com-
mon, that if either is disturbed without transgressing the range
of its stability, it will tend to reéstablish itself, but if the range is
overpassed it will topple over into a new position; also that both
of them are more likely to topple over towards the position of
primary stability, than away from it.

“The ultimate point to be illustrated is this. Though a long
established race habitually breeds true to its kind, subject to small

OTHER THEORIES OF SPECIES-FORMING. 361

unstable deviations, yet every now and then the offspring of these
deviations do not tend to revert, but possess some small stability
of their own. They, therefore, have the character of sub-types,
always, however, with a reserved tendency, under strained condi-
tions, to revert to the earlier type. The model further illustrates.
the fact that sometimes a sport may occur of such marked pecu-
liarity and stability as to rank as a new type, capable of becoming
the origin of a new race with very little assistance on the part of
natural selection. Also, that a new type may be reached without
any large single stride, but through a fortunate and rapid succession
of many small ones.

“The model is a polygonal slab, the polygon being one that
might have been described within an oval, and it is so shaped as
to stand on any one of its edges. When the slab rests, as in Fig 1,
on the edge A B, corresponding to the shorter diameter of the oval,
it stands in its most stable position, and in one from which it is.
equally difficult to dislodge it by a tilt either forwards or back-
wards. So long as it is merely tilted it will fall back on being
left alone, and its position when merely tilted corresponds to a simple
deviation. But when it is pushed with sufficient force, it will tumble
on to the next edge, B C, into a new position of stability. It will
rest there, but less securely than in its first position; moreover, its
range of stability will no longer be disposed symmetrically. A com-
paratively slight push from the front will suffice to make it tumble
back, a comparatively heavy push from behind is needed to make it
tumble forward. If it be tumbled over into a third position (not
shown in the figure), the process just described may recur with
exaggerated effect, and similarly for many subsequent ones. If,
however, the slab is at length brought to rest on the edge C D, most
nearly corresponding to its longest diameter, the next onward push,
which may be very slight, will suffice to topple it over into an
entirely new system of stability; in other words, a ‘sport’ comes
suddenly into existence. Or the figure might have been drawn with
its longest diameter passing into a projecting spur, so that a push
of extreme strength would be required to topple it entirely over.

“If the first position, A B, is taken to represent a type, the other
portions will represent sub-types. All the stable positions on the
same side of the longer diameter are subordinate to the first position.
On whichever of them the polygon may stand, its principal tendency
on being seriously disturbed will be to fall back towards the first
position; yet each position is stable within certain limits.

“Consequently, the model illustrates how the following cond:-
tions may co-exist: (1) variability within narrow limits without
prejudice to the purity of the breed; (2) partly stable sub-types ;

362 DARWINISM TO-DAY.

(3) tendency, when much disturbed, to revert from a sub-type to
an earlier form; (4) occasional sports which may give rise to new
types.”

*° Emery, C., “Gedanken zur Descendenz- und Vererbungstheorie,”
Biolog. Centralbl., Vol. XIII, pp. 397-420, 1893.

*? Korschinsky, S., ‘Heterogenesis und Evolution,” Naturw.
Wochenscrift, Vol. XIV, pp. 273-278, 1899; also “‘Heterogenesis u.
Evolution,” Flora, oder Alig. Bot. Zeit., Erganzungsbd. 89, pp. 240-
368, IQOI.

7? De Vries, H., ‘Die Mutationstheorie,” Vol. I, 1901, Vol. II,
1903.

Blecaioss te at De Werres, H., “Species and Varieties, Their
discussions by Origin by Mutation” (ed. by MacDougal), 1905.
de Vries of spe- “De Vries, H., “Die Mutationstheorie,” Vol. I,
cies-forming, p. 150, I90I.

*® De Vries, H., “Die Mutationstheorie, Vol. I, p. 362, I9go1.

*® De Vries. H., “Species and Varieties,” p. 6.

*7 De Vries, H., ‘Species and Varieties,” pp. 8-9.

*® De Vries, H., ‘Species and Varieties,” p. Io.

*® De Vries, H., “Species and Varieties,” p. 13.

*° For an excellent exposition and discussion of the de Vries muta-
tion theory and mutations, see Lotsy, J. P., ““Vorlesungen uber De-
scendenztheorien,” Vol. I, chaps. xiv and xv, 1906.

** Morgan, T. H., “Evolution and Adaptation,” pp. 294-295, 1903.

** As evidence of the interest and favour with which American
biologists have received the theory, the six addresses on “the muta-

pee yo tion theory of organic evolution” delivered before the
opinion ofthe | American Society of Naturalists at Philadelphia,
mutations December 28, 1904, may be especially referred to.
theory, These addresses by naturalists distinguished for their
work in different phases of biology, as systematic and cecologic
botany, cytology, human anatomy, animal cecology, etc., are printed
in Science, N. S., Vol. XXI, pp. 521-543 (April 7, 1905), and from
them I quote various paragraphs indicating some of the points
of view of the speakers and some of the arguments advanced in
favour of the theory.

“On the whole, it appears that the formation of new breeds be-
gins with the discovery of an exceptional individual, or with the
production of such an individual by means of cross-breeding. Such
exceptional individuals are mutations” (Castle, p. 524).

“Modification of character by selection, when sharply alternative
conditions (2. e., mutations) are not present in the stock, is an
exceeding difficult and slow process, and its results of questionable
permanency. Even in so-called ‘improved’ breeds, which are sup-

OTHER THEORIES OF SPECIES-FORMING. 363

posed to have been produced by this process, it is more probable
that the result obtained represents the summation of a series of
mutations rather than of a series of ordinary fluctuating variations.
For mutations are permanent: variations transitory” (Castle, p.
524).

“Tt is to my mind impossible to find any support for a theory of
evolution by minute changes from the study of anatomical varia-
tions. I should not venture to say, on the other hand, that they
give any direct support to the theory of mutation: but, at least, they
are not in disaccord with it” (Dwight, p. 532).

“Tt seemed necessary to discuss ethological characters at some
length for the purpose of vindicating their importance. Having
attempted this, I may say that these characters seem to me to offer
even fewer difficulties than the morphological characters to the
acceptance of the mutation theory, for the reason that the ethological
and psychological processes are conceived primarily as qualities
and not quantities. Thus the psychical elements, 7. ¢., the simple
feelings, cravings, and sensations, are disparate qualitative processes
which cannot be derived from one another or from some more
undifferentiated process. This is still more evident in the case of the
complex psychical phenomena. Similarly, instincts, with which
ethology is most concerned, when resolved into their simplest com-
ponents are seen to consist of discrete reactions which cannot be
shown to arise from one another. Although, on the other hand,
the measurable intensities and durations of the reactions are anal-
ogous to the fluctuating structural variations, it is even more difficult
for the psychologist to conceive of a particular feeling, craving,
or sensation as arising from the greater or less intensity or dura-
tion of some other psychic process, than it is for the morphologist
to conceive of the origin of new characters from the fluctuating
variations of structure’ (Wheeler, p. 539).

“Mutation is even more urgently demanded for the explanation
of many other instincts, especially those of symbiotic and parasitic
species and of species with profound and sudden metamorphosis.
In these cases, a particular activity, on which most often depends
the life of the individual or of its progeny, has to be performed
with a high degree of proficiency at its very phylogenetic incep-
tion or it can be of no advantage to the individual or the race.
Such cases, with which you are all familiar, have ever been the
insurmountable obstacle to the evolution of instincts on the theory
of fluctuating variations and natural selection. The theory of
organic selection seems to me merely to conceal but not to over-
come the difficulties. The mutation theory frankly avoids the diffi-
culties even if it fails to throw any light on the origin of the muta-

364 DARWINISM TO-DAY.

tions and bundles this into the germ-plasma. It is, of course, no
objection to the theory that it leaves something under the heavens to
be accounted for. This is rather to be regarded as one of its chief
virtues. As working naturalists we have reason to be most sus-
picious of the theories that explain everything’ (Wheeler, pp. 539-
540).

“In view of the amount of orderly and- well-authenticated evi-
dence now at hand, it may be regarded as demonstrated that char-
acters, of appreciable physiological value, originate, appear in new
combinations or become latent, in hereditary series of organisms,
in such a manner as to constitute distinct breaks in descent” (Mac-
Dougal, p. 540).

23 Some of de Vries’s experiments and observations on the La-
marck primrose have been repeated (with naturally some variation)
in the New York Botanic Garden, by MacDougal and assistants.
See MacDougal, D. T., “Mutation in Plants,” Amer. Nat., Vol.
XXXVII, pp. 737-770, 1903; also, “Mutants and Hybrids of the
CEnotheras,’ by D. T. MacDougal, assisted by A. M. Vail,
G. H. Shull, and J. K. Small, Pub. No. 24, Carnegie Inst. of Wash.,
1905.

I am aware of the rather sweeping statements made by some
biologists touching the probability of the origin by mutation of many
species, or at least, races of animals and plants. For example,
Castle (Science, N. S., Vol. XXI, p. 522; 1905) says:—"So far,
however, as these varicus sorts of evidence go, they indicate that
the material used by breeders for the formation of new breeds con-
sists almost exclusively of mutations.’ And Davenport (Science,
N. S., Vol. XXII, p. 372, 1905) says: “Undoubtedly many, if not
most, of the characteristics of the races of domesticated animals and
probably feral species have arisen by mutation.” He then refers,
as example, to the qualities that differentiate the races of poultry—
feathered feet, rose comb, elongated tail, taillessness, silky
feathers, frizzled feathers, cerebral hernia, polydactyl feet, albinism,
and many others. But I have been assured by Luther Burbank,
the most experienced and distinguished plant breeder in this country,
that the many races of plants actually produced by him have not
been derived from mutations. But on the contrary, that the selec-
tion of small variations—a special abundance and variety of these
variations usually being induced by hybridisation and by change of
environment—has been his almost exclusively relied-on means for
producing new forms of plants. As a matter of fact the cases.
actually adduced by upholders of the de Vriesian theory as supports
for it are astonishingly few. Castle (Science, N. S., Vol. XXI, pp.
522-523, 1905) calls attention to the sudden appearance of a super-

oo. ie

OTHER THEORIES OF SPECIES-FORMING. 365

numerary fourth digit on one of the hind feet of one of nine young
produced by a certain pair of guinea-pigs. ‘Neither of the parents
had such a digit, nor had I ever heard of the existence of such a
character before, either in any of the wild Caviede or among domes-
ticated cavies or guinea-pigs. Further, I have been able to find
no reference to such a thing in the literature of the group, though
I have several times simce found this same mutation in other herds
of guinea-pigs. The mother of my four-toed pig never produced
another similar individual, though she was the mother in all of
thirty young. The father, however, who sired in all 139 young,
had five other young with extra toes, but these were all by females
descended from himself, so that it seems certain that the mutation
had its origin in this particular male. By breeding together the four-
toed young and selecting only the best of their offspring, I was able
within three generations to establish a race with a well-developed
fourth toe on either hind foot. This race was not created by selec-
tion, though it was improved by that means.” Castle also had
another mutation appear in a second family of guinea-pigs. “A
few individuals were found to have hair about twice as long as
that of their parents and grandparents. Intermediate conditions did
not occur. Long-haired individuals mated together were found
to produce only long-haired young, so that a new breed was already
fully established without the exercise of any selection.” Casey
(Science, N. S., Vol. XXII, p. 308, 1905) presents a number of
facts touching the sudden appearance of certain molluscous genera
in early Eocene strata, and in certain Lower Oligocene rocks, which
seem to be evidence for the mutations theory. “At least, the
mutation theory is evidently the best that has been advanced to
account for these known facts.” Scott (Science, N. S., Vol. XXII.
pp. 271-282) attempts to make out a case for the mutational origin
of nine kinds of North American birds that, because of their rarity
and the obscure character of the records of their occurrence, are
mostly rather puzzling to ornithologists. (They are all included
in the “hypothetical list” of the American Ornithologists’ Union
Check-List.) But this attempt is robbed of much significance by
Allen’s critical discussion of it (Science, N. S., Vol. XXII, pp. 431-
434, 1905). Morgan (Harper’s Monthly Mag., Vol. CVI, p. 478)
refers to the “japanned” turkeys, a kind of bronze-shouldered aber-
ration that appears occasionally in flocks of turkeys, as “mutations.”
These turkeys are called attention to by Darwin (‘Variation of
Animals and Plants Under Domestication,” Vol. I, p. 305). Indeed,
more cases of such mutations are referred to and described by
Darwin himself than by all those who have attempted recently to
adduce examples, for the support of the mutations theory, of an

366 DARWINISM TO-DAY.

alleged case of sudden appearances of modified animals or plants
that seem to breed true. But these infrequent prepotent sports,
or discontinuous variations, do little to furnish any convincing
foundation for de Vries’s theory. Far better than all of them are
de Vries’s own long and carefully observed primrose mutations.
Here, besides a few single mutations, were several that appeared
in considerable numbers, which is a condition almost imperatively
necessary for the successful propagation of a new organic type.

A recent record of an alleged case of mutation is Schaffner’s,
“A Successful Mutant of Verbena without External Isolation,” in
Ohio Naturalist, Vol. VII, pp. 31-34, December, 1906.

As Davenport (“The Mutation Theory in Animal Evolution,”
Science, N. S., Vol. XXIV, pp. 556-558, November, 1906) puts it: “The
real argument for discontinuity in evolution is the occurrence of
characteristics in nature that are discontinuous and which never
show intergrades. The mere fact of discontinuity between species
of the same genus is not sufficient to prove that they have arisen
by mutation. It must be shown that the differential characters are
in essence discontinuous. The practical way to get at the true
nature of characteristics, whether continuous or discontinuous, is
by their behaviour in inheritance. If, in cross-breeding, a char-
acter tends to blend with the dissimilar character of its consort it
must be concluded that the character can be fractionised and inter-
grades are possible. If, on the contrary, the characteristic refuses
to blend, but comes out of the cross intact, as it went in, the con-
clusion seems justified that the characteristic is essentially integral
and must have arisen completely formed, and hence discon-
tinuously.

“Using this criterion, I have of late been testing the application
of the mutation theory to animals and have had an opportunity to
examine the experiments of others. Some of the work has been
done on the characteristics of domesticated ‘races,’ others on wild
varieties. There seems to be no difference in the behaviour of
characteristics of domesticated and wild varieties. The result is
that most characteristics, but not all, fail to blend and are strictly
alternative in inheritance. I interpret this to mean that the char-
acteristic depends on a certain molecular condition that does not
fractionise. The inference is that if the characteristic is incapable of
gradations now it has always been so and hence must have arisen
without gradations, 7. e., discontinuously. Examples of such discon-
tinuous characteristics are the spots in the elytra of certain beetles,
the crest on the canary, the form of the comb in poultry, extra toes,
black plumage, and colour of iris. One who sees the striking
failure of these characteristics and many others to be modified in

OTHER THEORIES OF SPECIES-FORMING. 367

any important way will feel convinced that they are not capable
of forming intergrades and hence could not have arisen gradu-
ally.”

24C, B. Davenport (“Evolution Without Mutation,” Jour. of
Exper. Zool., Vol. II, pp. 137-143, 1905), in a recent short paper,

adduces facts concerning the variation and evolution

Davenport's : :
examples of spe- of Pectens, which lead him to conclude that the races
cies-origin by of Pecten inhabiting different geographical regions
slight continu- are connected so plainly by integrating variations
ous change. that there can be no question of mutations in con-
nection with their origin. They must have arisen through evolu-
tion by trivial variation. Davenport concludes his paper with the
following summary: “The process of evolution has taken place by
various methods and not always in the same way. It is not more
justifiable to maintain that all evolution is by mutation than that
evolution has always proceeded by slow stages. The best evidence
for slow evolution is found in wide-ranging species which, while
differing greatly at the limits of their range, exhibit all gradations in
intermediate localities (Melospiza, Pecten); also in fossil series
(Pecten eboreus and P. trradians) where the change from one hori-
zon to the next is of a quantitative order. Thus evolution may take
place without mutation.”

Naturalists whose special field of study is systematic and fau-
nistic rather than morphologic or experimental, seem to be slow to

Mesias find much good in the mutations theory. Indeed,
criticism of the some of them seem to be quick to find much that is
mutations theory: j]] in it. For example, Merriam and Allen, deans of
American faunistic students of birds and mammals, are both strong
antagonists of the mutations theory. Merriam, in an address as
chairman of the zoological section at the 1905 meeting of the Ameri-
can Association for the Advancement of Science (“Is Mutation the
Factor in the Evolution of the Higher Vertebrates?” Science, N. S.,
Vol. XXIII, pp. 241-257, 1906), shows by the use of illustrations
drawn from the distribution and taxonomy of American chipmunks
and ground squirrels that the mutations theory cannot by any
means explain all species-forming. ‘My argument,” says Merriam,
“is not that species of plants may not in rare cases arise in perpetu-
ation of sport characters, as de Vries believes they do, but admitting
this, my contention is that the overwhelming majority of plants,
and so far as known, all animals, originate in the generally recog-
nised way by the gradual development of minute variations. The
theory of origin of species by mutation, therefore, far from being
a great principle in biology, as some seem to believe, appears to be
one of a hundred minor factors to be considered in rare cases as a

’

368 DARWINISM TO-DAY.

possible explanation of the origin of particular species of plants,
but so far as known, not applicable in the case of animals.”

Certain naturalists even go so far as to express some doubt about
the value of the mutations observed by de Vries in the primroses.
This doubt touches two points. First, the possibility that the
mutating primroses are not pure cultures, but are hybrids; second,
that when an investigation of the wild primroses in their native
locality (southern United States) is made it may be found
that these primroses in true wild condition do not mutate. Touch-
ing these two points, it should be said that de Vries has convinced
himself that his cultures are pure, and has tried to discover the
actual conditions existent among the primroses in their native
habitat. As a matter of fact, the Lamarckian primrose seems to be
practically extinct as a wild species. De Vries (“Uber die Dauer
der Mutationsperiode bei Gnothera Lamarckiana,” Ber. Deutsch. Bot.
Gesell., Vol. XXIII, pp. 382-387, 1905) found specimens of CEnothera
Lamarckiana in three botanical collections in the United States.
These specimens were collected in Florida and Kentucky. How-
ever, since these specimens were taken (the Florida ones in 1860)
the species has not been observed, perhaps on account of lack of
close observation, perhaps because actually disappeared. There-
fore the question whether the Lamarckian primrose mutates in
wild condition remains undecided.

*° The most considerable critical discussion and analysis of the
mutations theory is that made by Plate in his review of Morgan’s

Plate’s criti: | Evolution and Adaptation. (Plate, L., “Darwinismus
cism ofthe mu- kontra Mutationstheorie,”’ Archiv f. Rassen- und Ge-
tations theory. — se//schafts-Biologie, Vol. III, pp. 183-200, 1906.) In
the course of his critical review of Morgan’s book (which book
is at once an attack on Darwinism and an upholding of the muta-
tions theory), Plate points out keenly and strongly the weak places
in de Vries’s theory. As a general substitute for the natural selec-
tion theory as an explanation of adaptation as well as species-form-
ing, the mutations theory is open to many of the same objections as
the Darwinian theories. Plate takes up, serially, Morgan’s claims
for the mutation theory and readily shows their unconvincing char-
acter. I quote some of this analysis, as follows:

“Es ist von Interesse zu sehen, welche Grtinde Morgan bestim-
men, der Mutationstheorie trotz ihrer fundamentalen Mangel den
Vorzug zu geben vor der alten Darwin’schen Auffassung. Auf. S.
2908 zahlt er die ‘Vorztige’ dieser Theorie auf, die aber meines
Erachtens alle vor der Kritik nicht standhalten.

““t. Da die Mutationen von Anfang an vollstandig ausgebildet
auftreten, fallt die Schwierigkeit fort, die Anfangsstadien in der

OTHER THEORIES OF SPECIES-FORMING. 369

Entwicklung eines Organs zu erklaren, und da das Organ sich
erhalten kann, selbst wenn es keinen Wert fur die Rasse hat, kann
es durch spatere Mutationen weiter entwickelt werden und schliess-
lich eine wichtige Beziehung zum Leben des Individuums erlangen.’

“Die erwahnte Schwierigkeit, die Anfangsstadien niitzlicher Struk-
turen und Organe nach der Darwin’schen Auffassung zu erklaren,
lasst sich nicht leugnen, aber sie ist, wie ich in dem oben erwahnten *
Buche gezeigt zu haben glaube (S. 34-51), zu tiberwinden, besonders
dann, wenn man in der Vererbungsfrage Gegner von Weismann ist
und annimmt, dass ein durch Generationen ausgetibter Reiz sich in
seinem Effekt allmahlich steigert (Prinzip der Orthogenese) und
wenn man sich dartiber klar ist—was Morgan vollstandig entgangen
zu sein scheint—das der Konkurrenzkampf zwischen zwei Arten
sehr oft nicht sofort, sondern im Laufe von Generationen bloss
durch die grossere Fruchtbarkeit entschieden wird, diese aber kor-
relativ durch geringfigige morphologische Unterschiede und unbe-
deutende Anderungen in der Lebensweise wesentlich beeinflusst
werden kann. Durch die Mutationstheorie wird aber jene Schwie-
rigkeit in keiner Weise gehoben, denn erstens stellen die Mutationen,
wie auch Morgan zugibt, meistens geringfiigige Abanderungen dar,
welche die morphologische Breite der Fluktuationen nicht wber-
treffen. Man kann also nicht annehmen, dass das Stadium der
Nitzlichkeit mit einem Sprunge erreicht wird, dass etwa der
Rollrtissel des Schmetterlings plotzlich aus kauenden Kiefern
hervorging. Es mussten also eine Anzahl Mutationen in ganz
bestimmter Weise aufeinander folgen, was, wie eben schon ange-
deutet wurde, nach unsern jetzigen Kenntnissen von diesen regel-
und richtungslosen Variationen unmoglich ist.

“*2. Die neuen Mutationen konnen in zahlreichen Exemplaren
auftreten und von ihren verschiedenen Sorten werden diejenigen sich
erhalten, welche festen Fuss fassen konnen. Da dieselben Muta-
tionen zu wiederholten malen auftreten konnen, wird die Gefahr,
durch Kreuzung mit der Stammform vernichtet zu werden, im Ver-
haltnis zu der Zahl der neu auftretenden Individuen geringer.’ Dass
eine neue Mutation bei ihrem ersten Auftreten sofort in zahlreichen
Exemplaren erscheint, ist ein ausserst seltenes Vorkommnis. Mir
ist aus der Literatur nur der eine Fall der Whiteschen Washington-
Tomate bekannt, welche sofort zu 100% aus der Varietat Acme
zwei Jahre hintereinander auf derselben Lokalitat entstanden sein
soll. Die Mutationen der Gartenpflanzen sind alle von einer oder
einigen wenigen Stammexemplaren ausgegangen, waren also extreme

*Plate, Li. “Uber die Bedeutung der Darwin’schen Selections-
prinzip,” 1903.

370 DARWINISM TO-DAY.

Singularvariationen, und erst durch Isolation und Selbstbefruchtung
hat man grossere Mengen von Individuen erzielt. Die zoologischen
Mutationen weisen, soweit ihr Ursprung bekannt ist, immer auf
ein Stammtier: so das 1791 in Massachusetts entstandene Otterschaf,
die 1770 von einem hornlosen Stier ausgegangene Rinderasse in
Paraguay und die Rasse der Mauchampschafe, welche 1828 zuerst in
einem Lamm, das von Merino-Eltern abstammte, auftrat. Schwanz-
lose Katzen, Ziegen mit 4 Hornern, Menschen mit 6 Fingern sind
weitere Belege dafuir, dass solche sprungartige Abanderungen
grosste Seltenheiten sind. Da Selbstbefruchtung im Tierreich im
allgemeinen als ausgeschlossen gelten kann, so konnen solche Falle
nur durch grosste Inzucht und strengste Selektion zum Range einer
Rasse erhoben werden. Correns,* der selbst grosse Verdienste um
die Erkenntnis der Mutationen sich erworben hat, schreibt (S. 34)
iiber die Notwendigkeit der Selbstbefruchtung: ‘Es genugt aber
nicht, die Samen einer neu entstandenen Form zu sammeln und
auszusaen; es muss auch dafur Sorge getragen werden, dass diese
Samen ausschliesslich durch Selbstbefruchtung entstehen oder
wenigstens, wenn mehrere abgeanderte Individuen verwendbar
sind, durch Inzucht. Bei der Bestaubung der abgeanderten
neuen Pflanzen mit dem Pollen einer zur alten unverandert.
gebliebenen Form gehorenden Pflanze, die der Wind oder die
Insekten ausftihren konnen, entsteht ein Bastard zwischen der
neuen und der alten Form, indem die letztere fast immer die
erstere zunachst so vollkommen unterdruckt, dass der Bastard
genau wie die alte Form aussieht. Die neue Form kann dann
zwar in der folgenden Generation des Bastards wieder zum Vor-
schein kommen; in der Praxis beurteilt man aber die Erblichkeit nach
der ersten Generation.’ Wenn also in der freien Natur eine einzelne
Mutation auftritt, so wird sie als Regel mit der Stammform sich
kreuzen und Bastarde erzeugen, die entweder nach dem Mendelschen
Gesetz wie die Stammform aussehen oder den neuen Charakter in
abgeschwachtem Grade besitzen. Die meisten von diesen Bastarden
werden sich wieder mit der unveranderten Stammform kreuzen, da
deren Individuen weitaus in der Majoritat sind, und so muss der
neue Charakter in einigen Generationen wieder ausgelOscht werden,
selbst wenn er in der ersten Zeit in einzelnen Individuen ab und zu
zum Vorschein kommt.t Es gilt also meines Erachtens fiir die
Mutationen dieselbe Regel wie fur die Fluktuationen: Singular-

* Correns, C., ““Experimentelle Untersuchungen tiber die Entste-
hung der Arten auf botan. Gebiet.” Diese Zeitschr., I, 1904, S.
27-52. Wie man sieht, vertritt Correns hier die Dominanz der
phyletisch alteren Form.

f Vgl. hierzu S. 185, Anm.

OTHER THEORIES OF SPECIES-FORMING. 371

variationen spielen bei der Evolution keine Rolle, sondern nur
Pluralvariationen, wenn wit absehen von jenen vereinzelten Fallen,
in denen ein giinstiger Zufall fur die Isolation der Singularvariation
sorgt. Wahrend aber bei den Fluktuationen sich leicht eine neue
Rasse bilden kann, da immer viele Individuen nach dieser oder jener
Richtung vom Durchschnitt abweichen oder durch die ausseren
Faktoren in gleicher Weise verandert werden, liegen die Verhaltnisse
fur die Mutationen sehr viel ungiinstiger.

“3° Wenn die Zeit der Geschlechtsreife bei der neuen Form
abweicht von der der Elternform, vermag sich die neue Ari nicht
mit der Elternform zu kreuzen, und da dieser nette Charakter von
Anfang an vorhanden ist, wird die neue Form bessere Aussichten
haben am Leben zu bleiben als wenn der Zeitunterschied der Ge-
schlechtsreife erst allmahlich erworben werden miusste.’ Morgan
erwahnt hier eine ganz spezielle Form der sexuellen Isolation. Man
braucht jedoch nicht anzunehmen, dass dieselbe von den Fluktua-
tionen allmahlich erworben wird; sie ist entweder von vornherein
da, d. h. die neue Varietat wird in der Mehrzahl ihrer Individuen
friiher oder spater geschlechtsreif als die Stammform, oder diese
Schranke tritt tiberhaupt nicht auf. In diesem Punkte verhalten
sich also die Fluktuationen genau so wie die Mutationen.

“‘a. Die neuien Arten, welche erscheinen, konnen in einigen
Fallen schon an eine andere Umgebung angepasst sein als die von
der Stammform bewohnte; in diesem Falle werden sie von Anfang
an isolirt sein, was einen Vorzug bei der Vermeidung der schlechten
Einfltisse der Kreuzung bedeutet.’ Auch diese biologische Isolation
gilt natiirlich in demselben Masse fiir die Fluktuationen, ja sie muss
bei ihnen eine weit grdssere Rolle spielen, denn nach der Darwin-
’schen Auffassung wandern gewisse Individuen allmahlich in ein.
neues Wohngebiet ein und passen sich auf Grund ihrer Variabilitat
an dieses im Laufe von Generationen an. Wenn aber unter den
Exemplaren einer in der Ebene lebenden Art plotzlich einige muta-
tive Individuen auftreten, welche fiir das Leben im Gebirge einge-
richtet sind, so ist gar nicht zu verstehen, wie solche Mutationen
sofort die ihnen zusagende Wohnstatte resp. Lebensweise auffinden.

“5. Es ist wohl bekannt, dass die Unterschiede verwandter
Arten zum grossen Teile Differenzen unwichtiger Organe sind, und
dies steht in Harmonie mit der Mutationstheorie, bildet aber eine
der wirklichen Schwierigkeiten der Selektionstheorie.

“6. Nutzlose oder selbst leicht schadliche Charaktere k6nnen als
Mutationen auftreten und sich erhalten, wenn sie die Fortdauer der
Rasse nicht ernstlich beeinflussen.’

“Morgan muss sich wirklich sehr wenig in die Darwinischen
Gedanken eingearbeitet haben, wenn er nicht einsieht, dass die

a72 DARWINISM TO-DAY.

Selektionstheorie ttber den Ursprung der Variationen tberhaupt
nichts aussagt, sondern diese einfach als gegeben hinnimmt, mdgen
sie nur durch aussere Faktoren oder unbekannte innere Ursachen
hervorgerufen werden und mogen sie niutzlich, schadlich oder
indifferent ausfallen. In dieser Hinsicht steht sie auf demselben
Boden wie die Mutationstheorie, welche gleichfalls den Ursprung
der Mutationen nicht aufklart, sondern diese als pl6tzlich vorhanden
ansieht. Die Selektionstheorie sucht uns nur klar zu machen, wie
durch den Kampf ums Dasein die komplizirten ntitzlichen Ein-
richtungen, die Anpassungen, allmahlich entstehen konnten, und da
nahverwandte Arten haufig in dem Grade der Ausbildung solcher
Anpassungen—man denke z. B. an die Unterschiede zwischen dem
indischen und afrikanischen Elefanten im Bau der Rtisselspitze
und der Ohren—voneinander abweichen, macht sie bis zu einem ge-
wissen Grade auch den ‘origin of species’ verstandlich.* Morgan
wirft in seinem Buche immer und immer wieder ganz unberechtigter
Weise dem Darwinismus vor, er behaupte ‘That adaptations have
arisen because of their usefulness.’ Selbst die extremsten Anhanger
Darwins haben immer nur gesagt: gewisse Variationen bleiben
erhalten, weil sie nutzlich sind, und indem eine nttzliche Stufe zu
der andern allmahlich addirt wird, entstehen schliesslich jene
auffallenden Einrichtungen, die wir ‘Anpassungen’ nennen. Genau
denselben Standpunkt nimmt die Mutationstheorie ein. Auch fur
sie ist der Kampf ums Dasein—dieses Wort wie bei Darwin im
weitesten Sinne genommen—das oberste regulatorische Prinzip der
organischen Natur, welches die dauerfahigen Mutationen von den
schadlichen sondert, dadurch die Evolutionen in ganz bestimmte
Bahnen drangt und langsam die Entstehung der Anpassungen er-
moglicht. Dadurch dass der Kampf ums Dasein das ‘Uberleben des
Passendsten’ bedingt, schafft er etwas Positives und macht uns
die mit dem Wechsel der Lebensweise und Umgebung stets wech-
selnden Formen der Anpassungen verstandlich.”

7° Klebs, the eminent plant physiologist, keenly criticises the muta-
tions theory in his paper on “Willktirliche Entwicklungsanderungen
bei Pflanzen,” 1903. See also Copeland, E. B., ‘The Variation of
Some California Plants,’ Botan. Gaz. Vol. XXXVIII, pp. 401-426,
1904. In this paper the author describes some striking aberrant forms
of oak and fern leaves, but shows that between these mutation-like
forms and the modal forms intergrading steps exist. Copeland

* Es ist also nicht richtig, wenn Morgan (S. 454) von der Dar-
win’schen Theorie behauptet, sie werfe die Frage des Ursprungs
der Arten zusammen mit der des Ursprungs der Anpassungen.
og Probleme konnen zusammenfallen, aber sie brauchen es
nicht.

OTHER THEORIES OF SPECIES-FORMING. 373

discusses keenly the mutations of de Vries and finds in them noth-
ing radically different either in character or behaviour from the
Darwinian fluctuating variations.

** Conklin, E. C., Science, N. S., Vol. XXI, p. 525, 1905.

*° Morgan, “Evolution and Adaptation,” p. 292, 1903.

*° Morgan, “Evolution and Adaptation,” pp. 298-299, 1903.

Baoan ts °° Emery, C., “Gedanken zur Descendenz- und
theories explain- Vererbungstheorie,” Biolog. Centralblatt, Vol. XLV,
ing secondary PP. 397-420, 1893.
sexual characters: 51 Cunningham, J. T., “The Species, the Sex, and
ere Natural Science, Vol. XIII, pp. 184-192, 233-2390,
1808.

*? Wallace, A. R., “Tropical Nature,” 1878.

** Barrett-Hamilton, G. E. H., “Note on a Possible Mode of Origin
of some Nuptial and Sexual Characters in Vertebrates,” Anatom.
Anzetg., Vol. XVIII, pp. 47-48, 1900.

CHAPTER 21.
DARWINISM’S PRESENT STANDING,

A RIVER rises froma perennial spring on the mountain side ;
gravitation compels the water to keep moving, and rock

Natural selec Walls, intervening hills, and soft loam banks
artis determine the course of the stream. The living
descent. stream of descent finds its never-failing primal
source in ever-appearing variations; the eternal flux of
Nature, coupled with this inevitable primal variation, com-
pels the stream to keep always in motion, and selection
guides it along the ways of least resistance. Although there
can be no modification, no evolution, without variation, yet
neither can this variation, whatever its character and extent,
whether slight and fluctuating, large and mutational, de-
terminate or fortuitous, long compel descent to go contrary
to adaptation. And the guardian of the course is natural
selection. Selection will inexorably bar the forward move-
ment, will certainly extinguish the direction of any ortho-
genetic process, Nagelian, Eimerian, or de Vriesian, which is
not fit, that is, not adaptive. Darwinism, then, as the natural
selection of the fit, the final arbiter in descent control,
stands unscathed, clear and high above the obscuring cloud
of battle. At least, so it seems to me. But Darwinism, as.
the all-sufficient or even most important causo-mechanical \

planation of descent, is discredited and cast down.’ At
least, again, so it seems to me. But Darwin himself claimed
no Allmacht for selection. Darwin may well cry to be saved
from his friends!

374

DARWINISM’S PRESENT STANDING. + 235

The selection theories do not satisfy present-day biolo-
gists* as efficient causal explanations of species-trans-
ee formation. The fluctuating variations are not
selection nota sufficient handles for natural selection; the
marge hed hosts of trivial, indifferent species differences
forming, are not the result of an adaptively selecting
agent. On the other hand the declarations of Korschinsky,
Wolff, Driesch, and others that natural selection is non-
existent, is a vagary, a form of speech, or a negligible influ-
ence in descent, are unconvincing; they are unproved. /

And these bitter antagonists of selection are especially un-
convincing when they come to offer a replacing theory, an

ie eetiaue alternative explanation of transformation and
of the replacing descent. To my mind every theory of hetero-
SHEE: genesis, of orthogenesis, or of modification by
the transmission of acquired characters, confesses itself ulti-
mately subordinate to the natural selection theory. How-
ever independent of selection and Darwinism may be the
beginnings of modification, the incipiency of new species
and of new lines of descent; even, indeed, however neces-
sary to natural selection some auxiliary or supporting
theory to account for the beginnings of change confessedly
is, the working factor or influence postulated by any such
auxiliary theory soon finds its independence lost, its influ-
ence in evolution dominated and controlled by natural selec-
tion. As soon as the new modifications, the new species
characters, the new lines of descent, if they may come so
far, attain that degree of development where they have to
submit to the test of utility, of fitness, just there they are
practically delivered over to the tender mercies of selection.
No orthogenetic line of descent can persist in a direction
not adaptive, that is, not fit, and certainly no present-day
biologist is ready to fall back on the long deserted stand-
point of teleology and ascribe to heterogenesis or ortho-
genesis an auto-determination toward adaptiveness and

376 DARWINISM TO-DAY.

fitness. Modification and development may have been
proved to occur along determinate lines without the aid of
natural selection. I believe they have. But such develop-
ment cannot have an aim; it cannot be assumed to be
directed toward advance; there is no independent progress
upward, 7. e., toward higher specialisation. At least, there
is no scientific proof of any such capacity in organisms.
Natural selection * remains the one causo-mechanical ex-
planation of the large and general progress toward fitness;
the movement toward specialisation; that is, descent as we
know it.

But what Darwinism does not do is to explain the begin-
nings of change, the modifications in indifferent characters
An explanation and in indifferent directions. And all this 1s
ele re tremendously important, for there are among

ge is

needed, animals and plants hosts of existent indifferent
characters, and many apparently indifferent directions of
specialisation. As to the obvious necessity of beginnings
nothing need be said. What is needed, then, is a satisfactory
explanation of the pre-useful and pre-hurtful stages in the
modifications of organisms: an explanation to relieve Dar-
winism of its necessity of asking natural selection to find
in the fluctuating individual variations a handle for its
action; an explanation of how there ever comes to be a
handle of advantage or disadvantage of life-and-death-
determining degree. With such an explanation in our
possession—and whether any one or more of the various
theories proposed to fill this need, such as Eimerian
orthogenesis, de Vriesian heterogenesis, Rouxian battle of
the parts, or Weismannian germinal selection, etc., give
us this explanation, may be left for the moment undebated
—with such a satisfactory explanation, I say, once in our
hands, we may depend with confidence on natural selection
to do the rest of the work called for by the great theory
of descent. Among all the divergent lines of development

DARWINISM’S PRESENT STANDING, 377

and change, instituted by this agent of beginnings, natural
selection will choose those to persist by saying No to those
that may not. And the result is organic evolution.
But all this is equivalent to saying that there are other
important factors in descent than selection, and that as to
the beginnings of descent—and this is species-
The causes of : .
variation and the forming—these other factors are the more im-
San hate portant ones. Which I behéve: is: true; Te
factors inspe- Causes of variation and the means of segrega-
oies-forming» ~~ tion or isolation are the chief factors in actual
species-forming. Certainly the mutations theory is not yet
ready to offer itself as an explanation of adaptation, how-
ever confidently it may claim to be enrolled among species-
forming factors. The very same objections that have served
to topple down selection from its high seat of honour, can be
directed immediately and effectively against this latest claim-
ant for recognition as the Great Cause of descent. Nor can
geographical isolation explain modification where adaptation
is included. Nor can Lamarck’s beautiful explanation of
adaptation claim validity, until the actuality of its funda-
mental postulate, the carrying over of ontogenic acquire-
ments into phylogeny, be proved. And so with Buffon and
St. Hilaire’s influence of the ambient medium, and Eimer’s
modifying factors. Nor can any Nagelian automatic per-
fecting principle hold our suffrage for a moment unless we
stand with theologists on the insecure basis of teleology.
No, let no ambitious student hesitate to take up the

search for the truth about evolution from the notion that,
biology is a read book. The “Origin of Spe-}

Theunknown | ;
factors ofevolu- Cies’ was the first opening of the book—that

wan: the world recognised at least; poor Lamarck

opened the book but could not make the world read in it—

and that time when it shall be closed because read through
is too far away even to speculate about. With Osborn * let
us join the believers in the “unknown factors in evolution.”

378 DARWINISM TO-DAY.

Let us begin our motto with Jgnoramus, but never follow
it with [gnoribimus.

Now if we do not know, but want to know, and are willing
to make an attempt toward knowing, where shall our energy

Prime needs 01 €XPloration and discovery be first directed ? *
of evolution To what particular points or aspects of the
ama: causes-of-evolution problem shall we give our
first attention, what fields of study first invade? What, in a
word, is the principal desideratum in present-day investiga-
tion of evolution? I should answer, the intensive study of
variability, Not alone of the statics of variation but of its
dynamics. Indeed, above all its dynamics. The experimental
study of the stimuli, external and internal, the influences,
extrinsic and intrinsic, which are the factors and causes of
variation,—this is the great desideratum; this the crying call
to the evolution student. Experiment in variation study
includes controlled modification of ontogeny (experimental
development) and controlled modification of phylogeny
(pedigreed breeding). In the study of variation statics,
biometry is the greatest advance in modern methods, and
the essential basis of biometric study, namely, quantitative
and statistical data, must have its part in the investigation
of variation dynamics. But in entering the realm of the
causal study of variability, “we must not,” as Roux has
clearly pointed out, “conceal from ourselves the fact that
the causal investigation of organism is one of the most
difficult, if not the most difficult, problem which the human
intellect has attempted to solve, and that this investigation,
like every causal science, can never reach completeness,
since every new cause ascertained only gives rise to fresh
questions concerning the cause of this cause.”

I believe that the neglect on the part of the selectionists to
pay sufficient attention to the origin and causes of the varia-
tion which is such an indispensable basis of their theory, has
been one of the most obvious reasons for the present strong

DARWINISM’S PRESENT STANDING. 379

reaction against the selection theories. Thankfully accept-
ing the bricks and stones handed to them they have builded
Neglectof a house of great beauty: but with stones of
aun dg different shape a house of quite different ap-
tion, pearance might have been built. Is it not a
cause for wonder that the selection masons have not been
more inquisitive concerning the whence and why of this
magical supply of just the needed sort of material at just the
right time? As a matter of fact, Darwin himself gave
serious attention to the origin of his always-ready varia-
tions, but his tremendous undertaking was too nearly super-
human already to permit him to add to it an adequate
attention to the problem of causes. But that same excuse
does not attach to his followers. And it is, I repeat, largely |
this neglect to strive to penetrate the so-far unrent veil of
obscurity lying over the beginnings of species change that
has contributed to the growing revolt against the Allmacht
of the selection dogma. Who would in these days have a
following for his explanation of species origin must include
in his theory some fairly satisfying explanation of the first
visible beginnings of modification.

Then, after the explanation of the why and how of varia-
bility, comes the necessity of explaining the cumulation of
this variability along certain lines, the first visi-
ble issuance of these lines being as species, and
later becoming more and more pronounced as
courses of descent. This explanation has got to begin lower
down in phyletic history than natural selection can begin.
Before ever there can be utility and advantage there must
have come about a certain degree of heaping up, of cumu-
lating, of intensifying variations. What are these factors?
They are possibly only two: (1) orthogenetic or deter-
minate variation as the outcome of plasm preformation or
of epigenetic influences, and (2) the segregation of similar
variations by physiologic or topographic conditions. Hence,

How is varia-
tion cumulated ?

380 DARWINISM TO-DAY.

next to the cause or origin of variability the great desider-
atum is a knowledge of the means of cumulating and direct-
ing variability. And both these great fundamental needs
of a satisfactory understanding of organic evolution seem
to me to be wholly unreferred to in the theory of natural
selection. To be sure the control and cumulation of such
large differences among organisms and species as are posi-
tively sufficient to determine the saving or the loss of life
are explicable by selection. And this factor is sooner or later
in any phyletic history bound to step in and probably
be the dominant one. But a species, or a character, will
always have a longer or shorter preselective existence and
history, and it is precisely these days before the Inqui-
sition of which we demand information. For of one thing
we are now certain, and that is, that evolution and the origin
of species have both their beginnings and a certain period
of history before the day of the coming of the Grand
Inquisitor, selection.

Finally there is still another desideratum and one whose
seeking will carry us into dangerous country. For while
there may be and are selectionists who might allow us to
fumble about in the darkness of preselective time for first
causes, there is probably none who will allow us to ques-
tion his right to explain that other element in evolution be-
sides species transformation, namely, adaptation, or, as the
Germans untranslatably put it, Zweckmdassigkeit. But by
no means all biologists ° find in natural selection a sufficient
explanation of adaptation.

In the visible expression of organic evolution are two
chief elements, one the variety of life kinds, the existence of

tious species, the reality of lines of descent; and the
need ofexplain- Other the adaptedness and adaptiveness of these
ing adaptation. tife kinds. The varieties of organic kinds show
themselves adapted in structure and function to the varie-
ties of environment and life-conditions. Hence, the task

DARWINISM’S PRESENT STANDING. 381

of an evolution explanation is a double one; it must explain
not only diversity or variety in life, but adaptive diversity
or variety. And there is no gainsaying to the selection
explanation its claim to stand among all proposed explana-
tions of adaptation as that one least shaken by the critical
attack of its adversaries. However mightily the scientific
imagination must exert itself to deliver certain difficult
cases into the hands of selection, and however sophisticated
and lawyer-like the argument from the selection side may
be for any single refractory example, the fact remains that
the selectionist seems to be able to stretch his explanation
to fit all adaptations with less danger of finding it brought
up against positive adverse facts than is possible to the
champion of any other so far proposed explanation. The
explanation of adaptation by natural selection steers wide
of teleology on one hand and of unproved assumptions con-
cerning heredity on the other. The protoplasmic conscious-
ness of Cope and the automatic perfecting principle of
Nageli and those of his manner of explanation, are only
indirect ways of attributing to natural forces visions and
anticipations of what does not yet exist; while the influence
of the ambient medium of St. Hilaire and of the extrinsic
factors of Eimer, and the impressing photographically on
the species and the carrying over into phylogeny, with
approximate identity, of characteristics and modifications
acquired ontogenetically by the individual as a result of
functional stimulation—all these are assumptions not only
apparently unproved, but in the light of our present
knowledge of the mechanism of heredity seemingly un-
provable.

Yet the explanation of species transformation and of
adaptation by the introduction into phylogeny of modifica-
tions (reaction effects) arising in the individual during its
ontogeny, has to its credit a certain logical proof, or
basis, which has great validity in my mind, and yet which

382 DARWINISM TO-DAY.

has enjoyed little general recognition and almost no em-
phasis from supporters of Lamarckism or neo-Lamarckism.
As the great strength of the natural selection explanation of
species-change and adaptation lies precisely in the logical
nature of its premises and conclusions rather than on scien-
tific observation and experiment,’ it certainly is not unfair
to emphasise any similar kind of proof tending to support
the Lamarckian type of explanation.

The logical proof that I refer to is simply this: It is a
universally admitted fact that environment and functional

A logical proof stimulation can and do modify organisms dur-
nine ing their lifetime, and that this modification
ony of adaptive jis usually plainly adaptive. It is also an
ontogenetic ; ; ix d
changes. admitted fact that species differences or modi-
fications are often identical with these cntogenetic modifica-
tions. That is, that under similar environment or life
conditions species modification often follows the same lines
as ontogenetic or individual modification. Now when we
recall the possibilities of the hosts of ways in which the
necessities of adaptation to varying environment might be
met by selection among nearly infinite fortuitous variations,
and yet see that exactly that means or line or kind of adapt-
ive change occurs, which in the case of the individual is
plainly and confessedly a direct personal adaptive reaction
to varying environment, is it not the logical conclusion that
the species change and adaptation is derived, not by the
chance appearance of the needed variation, but by the com-
pelled or determined appearance of this variation? In other
words when species differences and adaptations are identical
with differences and modifications readily directly produci-
ble in the individual by varying environment, are we not
justified, on the basis of logical deduction, to assume the
transmutation of ontogenetic acquirements into phyletic
acquirements, even though we are-as yet ignorant of the
physico-chemical or vital mechanism capable of effecting the

DARWINISM’S PRESENT STANDING. 383,

carrying over? Has natural selection’s claimed capacity to
effect species change, unseen by observer, untested by exper-
imenter, any better or even other proof of actuality than
that just offered on behalf of species modification as a direct
result of the stimulus of varying environment and func-
tional exercise? I cannot see that it has.

And this kind of argument, based half on observed facts
and half on deduction, may be extended even farther on

ee Or behalf of the theory that species change is the
of proof fornon- direct reaction to environmental conditions.
adaptive change. Tor there are many ontogenetic variations pro-
duced directly in response to environment that are not
plainly adaptive; many, indeed, between which and the
environmental conditions that produce them no reasonable
relation is apparent; no relation, that is, that would be ex-
actly expected or could be foretold until empirically deter-
mined. In other words, many apparently non-significant
ontogenetic differences or variations appear as direct result
of environmental influence or stimulus. For example, indi-
viduals of certain species of the Crustacean phyllopod genus
Artemia show marked structural differences when grown
in salt water of varying density. These differences are in
the size and shape of the plate-like lateral gills, the seg-
mentation of the post-abdomen, the length of the caudal
flaps (telson) and the hairiness of these flaps. The size of
the whole body is also affected, individuals developing in
water of higher density being markedly smaller than those.
which have been grown in less dense water. Now of all
these differences only two seem to have what I call a rea-
sonable relation to the environmental differences. The in-
creased proportional size of the gills shown by the Artemias.
grown in denser water appears to be a regulatory change
connected with the smaller amount of oxygen in the water,.
and the decreased size of the body may similarly be con-:
ceived by some to be an expected concomitant of the:

384 DARWINISM TO-DAY.

denser water condition. -But what of the extra abdominal
segment, the longer telson projections and their increased
hairiness, all of which as shown by Schmankewitsch * (how-
ever mistakenly this investigator may have interpreted his
results as examples of actual species modification) and
Anikin® for Artemia salina and by the writer’? for Artemia
franciscanus, are the ontogenetic differences that varying
density of salt water actually produces in individuals of a
single Artemia species. These differences, these variations,
are of the sort that I am calling non-significant, non-adapt-
ive, non-reasonable. They would not be prophesied; they
seem to have no reasonable correlation with the causes
which produce them. But they are actually the results or
effects of determined proximate causes which are extrinsic
or environmental. If now the logical argument (based on
identity of adaptive modification in individuals and in spe-
cies) for the transmutation of ontogenetic changes into
phyletic changes has any validity, then these non-adaptive,
indifferent modifications may be transmuted as well as the
adaptive ones, and thus hosts of trivial, non-adaptive indif-
ferent species differences be explained on this Lamarcko-
Eimerian basis as well as the obviously adaptive modifica-
tions. But I am not insisting on this sort of argument too
strongly. It is exactly the sort of argument upon which the
theory of natural selection chiefly rests, and I have cer-
tainly tried to make evident in this book my belief in the
danger of the substitution of this sort of logical or meta-
physical basis of belief in a theory for a scientific basis of
observation and experiment.

Finally, let us ask ourselves why we have adopted the
common belief that our search for a cause of variability is a

Asuggestion Search for some so far unknown, some quite
0s grea new factor or force in biology? May it not be
tion. that the factor is already familiar to us; so
familiar indeed perhaps that we are esteeming it too simple

DARWINISM’S PRESENT STANDING. 385

and too obvious to play the rdle of the Great Desideratum,
a causal factor of variability.

When one attempts to picture the process of the making
of a new individual, and follows the complex phenomena of
fecundation, of embryology, and post-embryonic develop-
ment, is it not impossible to conceive of the production of
two identical individuals? In all the course of this develop-
ment, from the first cleavage of the fertilised egg-cell on,
it is practically impossible to repeat processes absolutely
identically, hence to produce absolutely identical organs,
parts, cells. Now the germ-cells have their very origin in
a repeated complex process, mitotic cell division; they are
produced as nearly alike as possible, but it is not possible
to make them absolutely identical.

Development, whether largely epigenetic or largely evo-
lutionary, depends at least partly (probably largely) on the
physical, 7. e., structural, character of the germ-cells. Slight
differences in the germ-cells then would lead to considera-
ble differences in the fully developed organ. If the differ-
ences in the germ-cells happened, as would occasionally or
rarely be the case, to be considerable, then the differences in
the adults would be very considerable (mutations, sports,
monsters, etc.). We know enough of the complex and
epigenetic character of ontogeny to see plainly that identity
among individuals, even of the same brood, is impossible.

Variation, then, seems the necessary, the absolutely un-
avoidable outcome of the conditions to which the developing
individual is exposed. Indeed, all the individuals of a
species might start (as fertilised eggs) exactly alike, and
yet I cannot see how any two could come out alike. The
inevitable slight differences in position, and hence in nutri-
tion, in the results of the host of dividing and folding, in-
vaginating and evaginating processes, the relations of each
individual, whether in the mother’s body or out of it, to
everything else outside of itself—all these are conditions

386 DARWINISM TO-DAY.

bound to vary a little between any two individuals. And as
we know from the facts of experimental embryology that
development is, partly at least, epigenetic in character, 1.e.,
depends on and is influenced by external factors, this in-
evitable variation in influencing conditions is bound to pro-
duce variations in the individuals.

Is there, indeed, any need at all for assuming (1) any
mysterious “tendency” of the germ-plasm to vary? and (2)
that the individual (continuous) variation depends wholly on
germ-plasm structure? Why cannot the simple fluctuating
or Darwinian variations be chiefly the result of the inevitable
variation in the epigenetic factors, which, when not intruded
on by exceptional disturbances, would themselves follow the
“law of error” and hence produce “law of error’ variabil-
ity? All normal swingings of the variation pendulum in
any part or character, between long and short, large and
small, round and angular, smooth and rough, etc., etc.,
would result from the normal variation of the processes; the
larger (extremes of range) variations being the fewer be-
cause the larger (extremes of range) variations in the
ontogenetic processes would be the fewer. Exceptionally
large epigenetic variations would produce exceptionally
large variations in the individual—sports, mutations.

Klebs,** as a result of his masterly experimental studies
on modifications of plant development, comes to the
conclusion that the only proved causes of variation are
extrinsic influences stimulating, working through, or com-
bined with, intrinsic conditions (not vitalistic, but physico-
chemical). Similarly, Tower,’* from his protracted studies
on the variations in certain insects, concludes that all these
variations are caused by external stimuli working on the
germ-plasm. .

If variation is thus simply the wholly natural and un-
avoidable effect ** of this inevitable non-identity of vital
process and environmental condition, why does not evolution

DARWINISM’S PRESENT STANDING. 387

possess in this state of affairs the much sought for, often
postulated, all-necessary, automatic modifying principle an-
See wiihviets tedating and preceding selection which must
thongh not pur- effect change, determinate though not purpose-
poseful change. F141? Nageli’s automatic perfecting principle is
an impossibility to the thorough-going evolutionist seeking
for a causo-mechanical explanation of change. But an
automatic modifying principle which results in determinate
or purposive change, that is, in the change needed as the
indispensable basis for the upbuilding of the great fabric of
species diversity and descent; is not that the very thing pro-
vided by the simple physical or mechanical impossibility of
perfect identity between process and environment in the case
of one individual and process and environment in the case
of any other? It seems so to me.

But I do not know. Nor in the present state of our knowl-
edge does any one know, nor will any one know until, as
Brooks ** says of another problem, we find out. We are
ignorant; terribly, immensely ignorant. And our work is,
to learn. To observe, to experiment, to tabulate, to induce,
to deduce. Biology was never a clearer or more inviting
field for fascinating, joyful, hopeful work. To question life
by new methods, from new angles, on closer terms, under
more precise conditions of control; this is the requirement
and the opportunity of the biologist of to-day. May his
generation hear some whisper from the Sphinx!

APPENDIX.

*One of the most serious and detailed critical analyses of the
selection theory, resulting in conclusions totally antagonistic to Dar-

Wigand’s criti- winism, is that of the Marburg botanist, Prof. Albert
cism of the selece Wigand, composing the three volumes entitled “Der
tion theories’ =Darwinismus und die Naturforschung Newtons und
Cuviers” (Vol. I, 1874; Vol. II, 1876; Vol. III, 1877). From the
“Announcements” at the beginning of each volume I quote as
follows:

388 DARWINISM TO-DAY.

From Vol. I. “Die hier dargebotene Kritik der Darwin’schen
Lehre weist zunachst durch eingehende Prufung der hierher ge-
horigen naturhistorischen Thatsachen nach, dass weder die Voraus-
setzungen, von denen die Theorie ausgeht, noch ihre Consequenzen
mit der wirklichen Natur tibereinstimmen, dass sie demnach den
Anforderungen an eine wissenschaftliche Hypothese nicht entspricht.
Vielmehr erweist sich dieselbe als eine philosophische Speculation,
welche nicht nur die unserer Naturerkenntniss vorgezeichneten
Grenzen tiberschreitet, sondern vor Allem die wichtigsten Grundsatze
der wahren Forschung, wie sie durch die grossen Meister aufgestellt
und in der bisherigen Entwickelung der Naturwissenschaft allgemein
anerkannt und unbedingt maassgebend gewesen sind, insbesondere
die Principien der Causalitat und der organischen Entwickelung, aufs
grobste verleugnet. Demnach erkennt das vorliegende Werk seine
Hauptaufgabe gerade darin, der bis dahin befolgten Forschungsweise
gegentiber jener neuesten Naturphilosophie ihr Recht zu wahren.”

From Vol. II. ‘‘Vermittelst der hierdurch gewonnenen Kriterien
gelangt die Untersuchung in Betreff des Darwinismus zu_ fol-
gendem Ergebnis: Derselbe geht nicht bloss von falschen Voraus-
setzungen aus, erweist sich nicht nur unfahig in Beziehung auf die
versprochenen Leistungen, ist nicht nur verfehlt durch die princi-
pielle Unmoglichkeit seiner Aufgabe, ist nicht nur eine der Natur-
forschung fremdartige, rein speculative Operation, sondern indem
derselbe das Princip der Causalitat und Entwickelung mit dem
Zufall und der Teleologie als Erklarungsgrunde vertauscht, erscheint
er als eine der Naturforschung in ihrer Fundamentalmaxime wider-
sprechende, darum dieselbe geradezu gefahrdende Verirrung, um
so mehr als er unter ihrer Maske auftritt. Der Darwinismus ist
einer jener Versuche, welche im Namen der Naturforschung die
Naturforschung verderben.”

From Vol. III. “Der vorliegende dritte Band, mit welchem dieses
Werk abschliesst, hat zum Gegenstand nicht die dem Darwinismus
zu Grunde liegende Theorie, sondern die concrete Gestalt, in welcher
derselbe als eine ftir unsere Zeit charakteristische culturhistorische
Thatsache in die Erscheinung tritt. Insbesondere wird versucht,
ein Bild von der Darwin’schen Schule als der Gesammtheit der die
Transmutationstheorie vertretenden Auctoren und von der Art und
Weise, wie sich die letztere im Lichte ihrer Bekenner darstellt, zu
entwerfen. MHierbei ergibt sich, dass der Darwinismus mehr in einer
ziellosen ZeitstrOmung und in einer wissenschaftlich nicht motivirten
Stimmung der Geister als in einer bestimmt zu formulirenden Lehre
besteht, und dass derselbe bereits in seinem eigenen Lager in allen
wesentlichen Punkten wissenschaftlich ttbherwunden ist, und zwar in
solcher Weise, dass in den widerstreitenden Ansichten der Darwin-

» 2. 9 ae
sg

DARWINISM’S PRESENT STANDING. 389

ianer doch zugleich der Keim fiir die allein richtige Auffassung der
organischen Natur, wenn auch grossentheils unklar und unbewusst,
verborgen liegt.”

A special answer to this exhaustive pleading of Wigand is offered
by H. Spitzer in his “Beitrage zur Descendenztheorie und zur Metho-
dologie der Naturwissenschaft,” 1886.

* However, there still exist, especially in England, thorough-
going Darwinians who see nothing serious in all this criticism of

Lankesters their great compatriot’s explanation of the origin of
upholding of species. Lankester, one of the most prominent of
Darwinism. English naturalists, said at York, last August (1906),
in his inaugural address as president of the British Association for
the Advancement of Science: ‘Under the title ‘Darwinism’ it is con-
venient to designate the various work of biologists tending to estab-
lish, develop or modify Mr. Darwin’s great theory of the origin of
species. In looking back over twenty-five years it seems to me that
we must say that the conclusions of Darwin as to the origin of
species by the survival of selected races in the struggle for exist-
ence are more firmly established than ever. And this because there
have been many attempts to gravely tamper with essential parts
of the fabric as he left it, and even to substitute conceptions for
those which he endeavoured to establish, at variance with his
conclusions. These attempts must, I think, be considered as having
failed.”

* “Physiologic facts concerning the origin of species in nature
were unknown in the time of Darwin. It was a happy idea to

De Vries's dis- Choose the experience of the breeders in the produc-
cussion of species- tion of new varieties, as a base on which to build an
forming by explanation of the processes of nature. In my opinion
oe Darwin was quite right, and he has succeeded in giv-
ing the desired proof. But the basis was a frail one, and would not
stand too close an examination. Of this Darwin was always well
aware. He has been prudent to the utmost, leaving many points
undecided, and among them especially the range of validity of his
several arguments. Unfortunately this prudence has not been
adopted by his followers. Without sufficient warrant they have laid
stress on one phase of the problem, quite overlooking the others.
Wallace has even gone so far in his zeal and ardent veneration for
Darwin, as to describe as Darwinism some things, which, in my
opinion, had never been a part of Darwin’s conceptions.

“The experience of the breeders was quite inadequate to the
use which Darwin made of it. It was neither scientific, nor critically
accurate. Laws of variation were barely conjectured; the different
types of variability were only imperfectly distinguished. The breed-

ence mes

390 DARWINISM TO-DAY.

ers’ conception was fairly sufficient for practical purposes, but science
needed a clear understanding of the factors in the general process
of variation. Repeatedly Darwin tried to formulate these causes,
but the evidence available did not meet his requirements.

“Quetelet’s law of variation had not yet been published. Mendel’s
claim of hereditary units, for the explanation of certain laws of
hybrids discovered by him, was not yet made. The clear distinction
between spontaneous and sudden changes, as compared with the
ever-present fluctuating variations, is only of late coming into recog-
nition by agriculturists. Innumerable minor points which go to elu-
cidate the breeders’ experience, were unknown in Darwin’s time.
No wonder that he made mistakes, and laid stress on modes of
descent which have since been proved to be of minor importance
or even of doubtful validity.

“Notwithstanding all these apparently unsurmountable difficulties,
Darwin discovered the great principle which rules the evolution of
organisms. It is the principle of natural selection. It is the sifting
out of all organisms of minor worth through the struggle for life.
It is only a sieve, and not a force of nature, no direct cause of
improvement, as many of Darwin’s adversaries, and unfortunately
many of his followers also, have so often asserted. It is only a
sieve, which decides which is to live, and what is to die. But evo-
lutionary lines are of great length, and the evolution of a flower, or
of an insectivorous plant is a way with many side-paths. It is the
sieve that keeps evolution on the main line. killing all, or nearly
all that try to go in other directions. By this means natural selec-
tion is the one directing cause of the broad lines of evolution.

“Of course, with the single steps of evolution it has nothing to
do. Only after the step has been taken, the sieve acts, eliminating
the unfit. The problem, as to how the individual steps are brought
about, is quite another side of the question’ (De Vries, “Species
and Varieties,” pp. 4-7, 1905).

The distinguished French zoologist (Professor in the University
of Paris), Delage. leader among French morphologists and experi-

Delage’s esti- menters, voices his position concerning Darwinism in
mate of selection. the following concise phrases (‘‘L’Hérédité,” 2d ed.,
Pp. 397, 1903): ‘‘La sélection naturelle est un principe admirable et
parfaitement juste. Tout le monde est d’accord aujourd’hui sur ce
point. Mais ot l’on n’est pas d’accord, c’est sur la limite de sa
puissance et sur la question de savoir si elle peut engendrer des
formes spécifiques nouvelles. 11 semble bien demontrer aujourd’hui
quelle ne le peut pas.”

*“A study of the recent discussion in the Contemporary Review
between Spencer and Weismann leads to the conclusion that neither

DARWINISM’S PRESENT STANDING. 39t

of these acknowledged leaders of biological thought supports his
position upon inductive evidence. Each displays his main force

Cctnrs's cham. 1 destructive criticism of his opponent; neither pre-
pionship of the sents his case constructively in such a manner as to
“anknown factors carry conviction either to his opponent or to others. In
of evolution.” = short, beneath the surface of fine controversial style
we discern these leaders respectively maintaining as finally estab-
lished theories which are less grounded upon fact than upon the
logical improbabilities of rival theories. Such a conclusion is deeply
significant; to my mind it marks a turning point in the history of
speculation, for certainly we shall not arrest research with any
evolution factor grounded upon logic rather than upon inductive
demonstration. A retrograde chapter in the history of science
would open if we should do so and should accept as established
laws which rest so largely upon negative reasoning... .

“The first step then towards progress is the straightforward con-
fession of the limits of our knowledge and of our present failure
to base either Lamarckism or neo-Darwinism as universal princi-
ples upon induction. The second is the recognition that all our
thinking still centres around the five working hypotheses which
have thus far been proposed; namely, those of Buffon, Lamarck, St.
Hilaire, Darwin, and Nageli. Modern criticism has highly differ-
entiated, but not essentially altered these hypothetical factors since
they were originally conceived. Darwin’s ‘survival of the fittest’
we may alone regard as absolutely demonstrated as a real factor,
without committing ourselves as to the ‘origin of fitness. The
third step is to recognise that there may be an unknown factor or
factors which will cause quite as great surprise as Darwin’s.” .

“The general conclusion we reach from a survey of the whole
field is, that for Buffon’s and Lamarck’s factors we have no theory
of heredity, while the original Darwin factor, or neo-Darwinism,
offers an inadequate explanation of evolution. If acquired varia-
tions are transmitted, there must be, therefore, some unknown
principle in heredity; if they are not transmitted, there must be
some unknown factor in evolution.” (Osborn, H. F., “The Un-
known Factors of Evolution,” in Wood’s Holl Biological Lectures,
Pp. 79, 80, 81, 98, and 99, 1894.)

° Davenport, C. B., “Animal Morphology in its Relation to Other
Sciences,” Congress of Arts and Sciences, Vol. V, pp. 244-257, 1900.
In this paper are pointed out in admirable manner the present-
moment problems, interests, and points of view of evolution biolo-
gists.

* Henry de Varigny, in “La Nature et La Vie,” 1905, says that for
many adaptations “il n’y a pas a se dissimuler que, dans beaucoup

’

392 DARWINISM TO-DAY.

de cas, cette explication [of the adaptation] est purement verbale ;
nous constatons un résultat. nous l’exprimons en essayant de 1’inter-
préter ; mais le mécanisme reste obscur. . . . Dans beaucoup de cas,
adaptation est un phénoméne que |!’on constate sans peine mais
qui dans l’état actuel de nos connaissances, reste sans explication”
(p. 184 and p. 185).

Klebs, Georg, “Willkurliche Entwicklungsanderungen bei Pflan-
zen,” 1903. An interesting, suggestive, and valuable account of

Klebs’s conclu- €XPeriments, and their significance, on altering the
sion from experi- developmental phenomena of plants. Although he is
ments on plants: strongly opposed to any vitalistic theory which attrib-
utes to life an independence of physico-chemical laws, Klebs does
not accept the Darwinian explanation of adaptiveness. Darwin
“betrachtet die Zweckmassigkeit selbst als den wesentlichsten Faktor
der Artbildung, indem nach seiner Meinung die naturliche Zucht-
wahl aus der Menge der richtungslos auftretenden variationen nur
die zweckmassigkeiten Merkmale zur Ausbildung und weiteren
Entfaltung bringt. Daher stammt die frither so verbreitete und
heute uns sonderbar erscheinende Meinung, dass die Deutung
eines Merkmales als eines zweckmassigen schon als eine Erklarung
fiir sein Entstehen und seine Ausbildung angenommen wurde. Die
Geltung der Darwin’schen Theorie muss seit den Arbeiten Nagelis,.
de Vries, u. a. jedenfalls eingeschrankt werden. Das eigentliche
Problem der Artbildung muss, wie wir spater sehen werden in
anderer Weise, formuliert werden” (p. 3).

Friedlander (‘““Entdeckung eines ‘Atlantischen Palolo,’” etc., Biol.
Centralbl., Vol. XXI, pp. 352-366, i901) refers to the Darwinian
explanation of Zweckmassigkeit as follows:

“Der ganze Darwinismus im weiteren, also auch vordarwin’schen
Sinne der Descendenzhypothese, mit oder ohne Betonung der Selek-

Friedlinder’s tionstheorie, und samt den allseitig als fertig und
discussion of sicher festgestellt gedachten Stammbaumen aller Or-
adaptation, ganismen, wtirde, wenn auch alles damit sonst seine
Richtigkeit hatte, unsere Gesamterkenntnis keineswegs in so tber-
massigem Grade bereichern, wie man fruher wahnte und vor allem
nicht in dem Masse, als dass es sich lohnte, auf die Herstellung
der zudem immer problematischen Stammbaume sonderliche Zeit und
Muhe zu verwenden. Zweitens aber haben die neueren Experimental-
forschungen Arten der Zweckmassigkeit an den Tag gebracht, welche
aus rein logischen Griinden durch die Selektionstheorie durchaus
nicht, auch nicht einmal scheinbar, ‘erklart’ werden kénnen. Nun
ist aber doch gerade die vermeintliche ‘Erklarung’ der organischen
Zweckmassigkeit oder sogen. ‘Anpassungsvollkommenheit’ die.
Hauptstarke des eigentlichen Darwinismus. Wie die Sache jetzt

DARWINISM’S PRESENT STANDING. 393:

liegt, miissten die Verteidiger des Darwinismus annehmen, dass die
organische Zweckmassigkeit zwei vollkommen verschiedene Wurzeln
habe. Die eine ware die alte Darwin’sche oder darwinistische—.
da namlich, wo diese logischerweise moglich ist; obwohl ja auch
hier die Erklarung die nicht recht befriedigende Form hat, dass.
gesagt wird, die Zweckmassigkeit rithre daher, dass die weniger
zweckmassigen Formen ausgestorben seien. Die zweite Wurzel der
organischen Zweckmiassigkeit, wie sie sich namentlich in den Selbst-
regulationserscheinungen aussert und zwar auch unter solchen
Bedingungen, die in der freien Natur kaum jemals vorkommen und
daher fiir das ‘Bestehender Art’ nicht von irgend welcher Bedeutung
sein k6nnen—diese zweite Wurzel der Zweckmassigkeit ist der
eigentliche Stein des Anstosses. Die Thatsachen sind hartnackig,.
eine darwinistische Scheinerklarung ist hier unmodglich und die an
sich doch so ausserst interessanten Erscheinungen, sowie die ganze
experimentelle Forschungsmethode ist bei den eigentlichen Dar-
winisten nicht in gutem Ansehen; aus dem sehr begreiflichen Grunde,.
weil jene Thatsachen ftir die betreffende Richtung unbequem sind.
Eine Reihe sicher festgestellter Thatsachen aus dem Gebiete der
sogen. Selbstregulation beweist also, dass es organische Zweck-
massigkeiten und obendrein typische Beispiele von solchen giebt,.
welche dem Darwin’schen Erklarungsschema vollkommen trotzen.
Nun aber hat die organische Zweckmassigkeit im ganzen ein so
einheitliches Geprage, dass ein doppelter Ursprung von vorn herein
ausserst unwahrscheinlich ist. Hieraus folgt dann weiter, dass die
darwinistische Betrachtungsweise in der Wirklichkeit wahrscheinlich
auch in den Fallen nicht zutrifft, wo sie logisch wenigstens die
Moglichkeit einer Erklarung oder Quasierklarung darzubieten
scheint. Endlich aber sollten auch diejenigen, denen die Bedenken
gegen die darwinistischen Schlussfolgerungen nicht recht eingehen
wollen, nachgerade doch wenigstens das einsehen, dass der Teil der
Biologie, der sich allenfalls im darwinistischen Sinne behandeln
liesse oder doch in Sinne jener Richtung nach Darwin’schen Prin-
zipien behandelt werden kann,—dass dieser Teil nur ein kleines.
und vergleichsweise auch unwichtiges Gebiet umfasst.”

“Jacques Loeb, in a recent address (‘‘Recent Development of
Biology,” Congress of Arts and Sciences, Vol. V, p. 17, 1906), takes
this attitude toward the problem of species-forming: “The theory

Loeb’s attitude Of heredity of Mendel and de Vries is in full har-
toward the prob- Mony with the idea of evolution. The modern idea
lem of species- of evolution originated, as is well known, with
forming, Lamarck, and it is the great merit of Darwin to have
revived this idea. It is, however, remarkable that none of the
Darwinian authors seemed to consider it necessary that the trans-

394 DARWINISM TO-DAY.

formation of species should be the object of direct observation. It
is generally understood in the natural sciences either that direct
observation should form the foundation of our conclusions or
mathematical laws, which are derived from direct observations. This
rule was evidently considered superfluous by those writing on the
hypothesis of evolution. Their scientific conscience was quieted by
the assumption that processes like that of evolution could not be
directly observed, as they occurred too slowly, and that for this
reason indirect observations must suffice. I believe that this lack
of direct observation explains the polemical character of this liter-
ature, for wherever we can base our conclusions upon direct obser-
vations polemics become superfluous. It was, therefore, a decided
progress when de Vries was able to show that the hereditary
changes of forms, so-called ‘mutations,’ can be directly observed, at
least in certain groups of organisms, and secondly, that these
changes take place in harmony with the idea that for definite
hereditary characteristics definite determinants, possibly in the form
of chemical compounds, must be present in the sexual cells. It seems
to me that the work of Mendel and de Vries and their successors
marks the beginning of a real theory of heredity and evolution. If
it is at all possible to produce new species artificially, I think that
the discoveries of Mendel and de Vries must be the starting point.”

* Schmankewitsch, A., Zeitschr. f. wiss. Zool., Vol. XXV, p. 103,
1875; also Zeitschr. f. wiss. Zool., Vol. XXIX, p. 429, 1877.

° Adelung, Zool-Centralbl., Vol. VI, p. 757, 1899. (A review of
Anikin’s paper, which is in Russian.)

1 Kellogg, V. L, “A New Artemia, and Its Life-Conditions,”
Science, N. S., Vol. XXIV, 594-596, 1906.

1 Klebs, G., “Willkiirliche Entwickelungsanderungen bei Pflan-
zen,’ 1903.

12 Tower, W. L., “Evolution in Chrysomelid Beetles of the Genus
Leptinotarsa,” Pub. No. 48, Carnegie Institution of Washington.

“The phenomenon of variation primarily owes its existence to the
fact that community of descent and heredity tends to produce the
exact counterpart of the parent organisms; the process of develop-
ment, however, is not carried out under absolutely constant or uni-
form conditions, but in a world wherein there exist changing environ-
mental states in endless proximity. This results in the turning
aside in the line of development from the parental standard, per-
haps ever so little or only in one character; but in this we have
deviation or variation” (p. 208).

“In the explanation of origin of variation in organisms the only
assumption we need make is that the original unit of organic matter
was possessed of the attributes which characterise organic matter

DARWINISM’S PRESENT STANDING. 395

to-day—motion, sensation, growth, and reproduction. This assump-
tion cannot meet with any serious objection unless we change our
ideas and definition of organic units. Granted the existence of one
single organic unit endowed as above, there is no reason for intro-
ducing further complications by the explanation of phenomena
through undemonstrable hypotheses, because the fact of variation in
organic units can be explained solely through their existence in a
natural world surrounded by varying conditions of existence”
(p. 299).

“In the third chapter, where colour characters are used as sub-
jects, it is demonstrated that variation is directly produced by
stimuli—that from relatively invariable parents, stimuli produce
variable offspring; and again in the fifth chapter it is shown that
variations arise in direct response to stimuli” (p. 300).

“TI maintain, therefore, that all organic variations are responsive
to stimuli, and are not due to inherent tendencies or latencies, or
the product of mystic elements” (p. 300).

18 Montgomery, T. A., in a recent book of much interest (‘‘Anal-
ysis of Racial Descent in Animals,” 1906), explains clearly his belief
in the inevitable production of variation (even that called blastogenic
or congenital), and the influence on heredity (through this varia-
tion) by the influences of environment.

14 Brooks, W. K., “The Foundations of Zoology,” p. 43, 1899. A
most thoughtful and keen discussion of many of the conspicuous
problems of “philosophical biology,” written in lucid and epigram-
matic style. In many ways Brooks stands at the head of American
philosophical biologists.

INDEX.

Adaptation, complex and cor-
related, not explicable by
selection, 144; Friedlander’s
discussion of, 392; lack of, in
egg-laying habit of Phrygani-
dia californica, 68; the great
need of explaining, 380; not
all explicable by Lamarckism,
272

Amphimixis, Weismann’s prin-
ciple of, 180

Anosia, mimicry of, by Basi-
larchia, 49

Anti-Darwinism, present-day, 4

Baldwin, J. M., theory of ortho-
plasy, 208

Basilarchia, mimicry of Anosia
by, 49

Bateson, W., records of discon-
tinuous variation, 33; sugges-
tion that mutations are Men-
delian recessives, 351

Battle of the parts,
theory of, 201

Biologists, many not satisfied
with the selection theory, 89

Biophor, 195

Brown-Séquard, experiments on
guinea pigs, 290

Buffon, theory of ultimate
structure of protoplasm, 216

Bumpus, H., example of in-
creased variability due to
emancipation from selection,
56; references to papers by, 69

Burbank, Luther, belief in La-
marckism, 272; scientific as-
pects of work of, 310

Roux’s

Callosamia promethea, Mayer’s
experiments with, 120

Carcinus, Weldon’s _ selection
experiments on, 158

Castle, W. S., discussion of
mutations theory, 364

Chance, law of, variation accord-
ing to, 32-59

Characters, numerous, useful
only in highly perfected state,
49; species, of no utility, 38

Colour and pattern of insects,
Piepers’ antagonism to selec-
tion explanation of,

Conn, H. W., discussion of the
chances of death, 83; discus-
sion of selective value, 182;
statement of objection to se-
lection, based on trivial char-
acters, 40

Cope, E. D., belief in ortho-
genetic evolution, 323; claim-
ing that natural selection can-
not make new characters, 185;
theory of orthogenesis, 285

Correlation, references to papers
on, 184

Crab, hermit and polyp, sym-
biosis of, 23

a Weldon’s experiments on,
15

Cunningham, J. T., criticism of
Weldon’s experiments on
erabs, . 160i. discussion) (of
orthogenesis, 326; experiments
on flatfishes, 296; explanation
of secondary sexual charac-
ters, 354; theory to explain sec-
ondary sexual differences, 124

Dall, W., belief in
species-change, 330
Darwin, C., attitude toward de-
terminate variation, 34; basis
of theory of sexual selection,
112; explanation of descent,
13; On race origin from sports,
357; theory of sexual selec-
tion, I11; theory of ultimate
structure of protoplasm, 218
Darwinism attacked, 25; attack
on, by Dennert, 7; concilia-

sudden

397

398

tory defence of, 164; death-bed
of, 1; defended, 129; defined,
2, 10; not synonymous with
organic evolution, 2, 3; pres-
ent standing of, 374; upheld
by Lankester, 389
Davenport, C. B., discussion of
mutations theory, 367
Death-bed of Darwinism, I
Death indiscriminate, 80
Defence of Darwinism, 129
Degeneration, complete, not ex-
plicable by selection, 77, 146;
example of progressive, not
explicable by natural selection,
100; explanation of, by pan-
mixia, 190; Lamarckian ex-
planation of, 192; Plate’s La-
marckian explanation of, 147;
Tayler’s Darwinian explana-
tion of, 147; Weismann’s dis-
cussion of, 77

Delage, Y., criticism of Del-
boeuf’s law, 72; criticism of
organic selection, 210; esti-

mate of selection, 93, 390; ma-
chine theory of protoplasm,
225; theory of general varia-
tion, 289

Delbceuf’s law,
cist of, 72

Dennert, E., attack on Darwin-
ism, 7

Descent, Darwinian explanation
of, 13; evidences for, 17; evi-
dences of, references, 23; his-
tory of theory of, references,
22; natural selection the final
arbiter in, 374; relations to
theology, references, 23; theo-
ries of, 187; theory of, de-
fined, 11; theory of, dis-
tinguished from theory of nat-
ural selection, 17; theory of,
history, of. 11; theory, given
validity by Darwin, 12; theory,
relation to pedagogy, 21;
theory, relation to sociology,
21; theory, relation to theology
and philosophy, 20

Determinant, 95

DeVries, H., belief of, that
artificial races are not fixed
and constant forms, 87; dis-
cussion of geologic time and

Delage’s criti-

INDEX.

species-forming, 54; discus-
sion of species-forming by
selection, 389; objection to
selection based on linear char-
acter of variation, 139; refer-
ences to discussions of muta-
tions theory by, 362; summing
up of discussion of compari-
son of natural and _ artificial
selection, 89; theory of muta-
tions, 337; theory of the ulti-
mate structure of protoplasm,
220

Dohrn, A., principle of change
of function, 168

Douglass, N. G., observations
on wall lizard, 123

Durigen, observations on_ liz-
ards,. 123

Eimer, Th., theory of ortho-
genesis, 282, 321

Emery, C., theory of primary
variations, 332; theory of the
origin of secondary sexual
characters, 353; theory to ex-
plain secondary sexual differ-
ences, 124

Evolution, defined, 10; organic,
not synonymous with Darwin-
ism, 2, 3; Osborn’s champion-
ship of the unknown factors
of, 391; the unknown factors
OF, 377

poe a study, prime needs of,
37

Fischer, experiments with but-
terflies, 296

Fleischmann, A., opposed to evo-
lution, 8

Friedlander, discussion of adap-
tation, 392

Friedman, H., theory of the con-
vergence of organisms, 8

Galton, F., belief in hetero-
genesis, 332; discussion of
specific stability, 359; discus-
sion of variation according to
the law of chance, 61; law of
regression, 71; statement of
the law of regression, 97

Germ-cells, theories of ultimate
composition of, 268

INDEX.

Grinnell, Jos. study of geo-
graphic differences in the
chickadee, 225

Gulick, J. T., studies of Ha-
waiian land snails, 251; theo-
ries of isolation influence, 249

Haacke, W., discussion of in-
heritance of acquired char-
acters, 270; summary of Wag-
ner’s theory, 253

Haeckel, E., champion of evolu-
tion, 130

Hatschek, B., theory of the
ultimate structure of proto-
plasm, 222

Henslow, G., experiment of sow-
ing of wheat, 80; references to
aoe antagonistic to selection,

Heterogenesis, 326; belief in, of
Dall, 330; Emery’s theory of,
332; Korschinsky’s theory of,
333; proposed by von Kol-

liker, 330

Hutton, F. W., argument for
dualism, 23

Hyatt, A. experiments on

Planorbis, 295

Inheritance of acquired char-
acters, 263; Brown-Séquard’s
experiments, 290; Cunning-
ham’s experiments, 296; diff-

_ culties in accepting, 267; ex-
periments with = silkworms,
2908; Fischer’s experiments,
296; Haacke’s discussion of,
270; Hyatt’s experiments, 295;
logical proof of, 382; Mont-
gomery’s explanation of, 306;
references to discussions of,
305

Insects, parthenogenetical varia-
tion in, 58; variation in, 62

Interbreeding, swamping favour-
able variations, 44

Intra-selection, Roux’s theory of,
201; Plate’s criticism of
Roux’s theory of, 203

Isolation, biologic, 243; biologic,
example of, 243; geographic,
studied among past animals,
241; defined, 234; importance
of, in species-forming, 232;

399:

not an all-sufficient agent of
species-forming, 242; physio-
logical, 245; references to dis-
cussions of, 253, 261; sexual,.
245; theories, 232; various.
means of effecting, 234

Jaeckel, theory of metakinesis,
289

Johannsen, W., experiments.
with beans bred in pure lines,

72
Jordan, Karl, criticism of Ver-
non’s theory of reproductive
divergence, 249; on mechanical
selection, 246
Jordan, D. S,,
isolation, 237

on geographic

Kallima, case of, explained by
Plate, 175; over-specialisation

of, 53
Klebs, G., experiments on plants,

392
Korschinsky, H., radical anti-
selection position of, 9QI;
theory of heterogenesis, 333
Kramer, P., classification of sec-
ondary sexual characters, 107

Lamarck, references to his life
and writings, 290

Lamarckism, 263; Burbank’s be-
lief in, 272; favoured by Red-
field, 305; Plate’s discussion
of, 273; unable to explain all
adaptations, 272; Weismann’s.
attack on, 266

Lankester, R., answer to objec-
tion to selection, based on in-
sufficient time, 55; upholding
of Darwinism, 389

Law, Delbceuf’s, Delage’s criti-
cisms of, 72; of chance, varia-
tion. according to, 32, 50; of
regression, Galton’s, 71; of
regression, statement of Gal-
ton, 97

Le Dantec, F., chemical theory
of protoplasm, 225

Lizards, experiments on, 123

Loeb, J., attitude toward the
problem of species-forming,.

393

400

Mallophaga, effects of isolation
on, 240

Mayer, A. G., experiments on
Promethea, 121; experiments
on sexual selection, 120

Mendel, G., references to life and
work, 356

Mendelism, references to discus-
sions of, 357

Merriam, C.. Hi ‘criticrm of
mutations theory, 367

Metakinesis, Jaeckel’s theory of,
289

Mimicry of Anosia by Basi-
larchia, 49

Montgomery, Th.,
of inheritance
characters, 306

Morgan, C. L., statement of con-
ception of organic selection,
230; theory of orthoplasy, 145,
208; answer to objections to
sexual selection theory, 149

Morgan, T. H., antagonism of
species-forming by selection,
93; criticism of Weismann’s
method of argument, 229; dis-
cussion of de Vries’s theory,
345; objections to sexual se-
lection theory, 118; summation
of the advantages of the muta-
tions theory. 350

Mutation, as used by Waagen,
324; de Vries’s theory of, 337

Mutations theory, American
opinion of, 362; attitude of
naturalists toward, 348; con-
trasted with Lamarckism, 349;
contrasted with the isolation
factor, 349; discussion of, by
Castle. 364; discussion of, by
Davenport, 366, 367; Mer-
riam’s criticism of, 367; Mor-
gan’s summation of the ad-

explanation
of acquired

vantages of, 350; Plate’s
criticism of, 368; references
to discussions of, by de

Vries, 362

Nageli, Ch., seven objections to
species-forming by selection,
62; theory of orthogenesis,
277; theory of ultimate struct-
ure of protoplasm, 219

INDEX,

Neo-Darwinians, concessions of,
<n |
Neo-vitalism, 226

Organisms, number of living, 10

Orthogenesis, 274; Cope’s belief
in, 323; Cope’s theory of, 285;
Cunningham’s discussion of,
326; Eimer’s theory of, 282,
320; Nageli’s theory of, 277;
paleontologists in favour of,
288; Ptieffer’s theory of 320-
Plate’s résumé of evidence for,
279; Whitman’s declaration in
favour of, 288

Orthoplasy, 208; references to
discussions of, 229

Orthoselection, contrasted with
orthogenesis, 276

Osborn, H. F., championship of
the unknown factors, of, 391;
theory of orthoplasy, 208

Paleontologists favouring ortho-
genesis, 288

Panmixia, example of ineffect-
ive, 99; Weismann’s theory of,
188: Wolff's criticism of, 98

Parallelism in variation, 279

Parthenogenesis, variation in in-
sects produced by, 58

Pearson, K., discussion of varia-
tion according to the law of
chance, 61; theory of repro-
ductive selection, 249

Pedagogy, relation of, to theory
of descent, 2

Pfeffer, G., objection to selec-
tion, based on the smallness of
species-change, 75; statement
of the fundamental difference
between natural and artificial
selection, 88; theory of ortho-
genesis, 320

Philosophy, relation to biology,
references for, 24; relation to
theory of descent, 20

Phryganidia californica, lack of
meee in egg-laying habit,
6.

Piepers, M. C., antagonism to
selection explanations of
colour and pattern in insects,

INDEX.

conclusions on species-form-
ing, 300, 394

Ultra-Darwinism,
against, 130
Utility, many species characters

of no, 38.

reaction

Variation according to the law
of chance, 32, 59; causes of,and
means of segregation the chief
factors in species-forming,
377; determinate, apparent
cases of, 319; determinate, as
a species-forming factor, 33;

determinate, produced by
germinal selection, 198; de-
terminate, Whitman’s _ belief
in, 325; discontinuous, 33,

328; favourable, swamped by
inter-breeding, 44; fluctuating,
as a basis for species-forming,
35; fluctuating, insignificance
of, 36; fluctuating, of linear
and quantitative value only,
139; fluctuating, too slight to
be of selective value, 138; gen-
eral, Delage’s theory of, 289;
how cumulated, 379; in in-
sects, 62; in parthenogenetic
insects, 58; natural selection
based on, 30; necessity for co-
incident appearance of other,
to make a certain one effect-
ive, 46; non-correlated in bi-
laterally repeated organs, 65;
occurrence of needed _ coin-
cident, 45; orthogenetic, in
paleontology, 319; parallelism
in, 279; references for, 57;
suggestion concerning the
cause of, 384

Vejodovsky, example of pro-
gressive degeneration not ex-
plicable by natural selection,
100

Vernon, H. M., theory of repro-
ductive divergence, 248 ; theory
of the ultimate structure of
protoplasm, 225

Vestigial structures, explanation

403

of, by panmixia, 190; La-

marckian explanation of, 192
Von Kolliker, R., proposal of a

theory of heterogenesis, 330

Waagen, use of term mutation,
324

Wagner, M., formulation of
Separations-theorie, 236;
founder of theory of species-
forming by geographic isola-
tion, 234

Wallace, A. R., criticism of Ro-
manes’s theory, 247; suggested
explanation of secondary
sexual characters, 354

Weismann, A., admission of ob-
jections to selection, 45; at-
tack on Lamarckism, 266; dis-
cussion of degeneration, 77;
principle of amphimixis, 180;
references to evolution writ-
ings of, 212; theory of germi-
nal selection, 188, 193; theories
of neo-Darwinism and _ neo-
Lamarckism;. 133% theory .of
panmixia, 188

Weldon, selection experiments
on Carcinus, 158

Whitman, C. O., belief in deter-
minate variation, 325; favour-
ing orthogenesis, 288

Wolff, G., attack on the assump-
tion by selectionists of the ap-
pearance at the right time of
the needed variation, 64;
criticism of panmixia by, 98;
criticism of sexual selection,
126; discussion of selection, co-
efficient, 101; objections to ex-
planation by selection of com-
plex related body-parts, 51;
objection to natural selection,
based upon its dependence on
sexual selection theory, 125;
objections to sexual selection
theory, 126; objection that
selection can concern only
quantitative changes, 70; ob-
jection to the assumption by
selectionists of identical and
coincident variation, 67

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Full text of "Darwinism to-day; a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxiliary and alternative theories of species-forming"

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