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Vernon L. (Vernon Lyman) Kellogg.

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 auxilary and alternative theories of species-forming online

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Online LibraryVernon L. (Vernon Lyman) KelloggDarwinism to-day; a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxilary and alternative theories of species-forming → online text (page 31 of 38)
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observations on amination of the stomach contents of over 200 indi-
bills of Q-ala- viduals, representing 13 species and sub-species (taken
pages birds. i TO m several of the Galapagos Islands) of the peculiar
Galapagos Fringillid genus, Geospisa, 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: (i) 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 I cubic millimetre up to those 15 mm. long
by 10 mm. thick. The bill of the different species and sub-species
of Geospisa, 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.

18 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.

11 "Palaeontologists, 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



3 2 4



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 is obvious that it has reached a point beyond which all
must be speculation. The facts on which the palaeontologist 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 palaeontologist, 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 ifi deter- man takes strong ground for orthogenesis and recites
minate variation. m 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."

28 Cunningham, an English neo-Lamarckian, expresses ("Origin
of Species Among Flatfishes," Natural Science, Vol. VI, p. 239,
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-
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."

24 Delage, Yves, "L'Heredite," 2d ed. p. 849, and others, 1903.

"Jaeckel, O., "Uber verschiedene Wege phylogenetischer Ent-
wicklung," 1902.



CHAPTER XL

OTHER THEORIES OF SPECIES-FORMING AND
DESCENT ( CONTINUED ) : ALTERNATIVE
THEORIES (CONTINUED).

Heter agenesis. 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,
is a 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 CE'notheras
(evening primroses), there have been much associated in
recent popular scientific literature accounts of the ear-
lier observations of Gregor Mendel, 1 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



32 8 DARWINISM TO-DAY.

nection, to observations and experiments carried on nearly
simultaneously with those of de Vries by Correns 2 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 ones 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
vSSiol?* su dden 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," i. e., considerable
variations not connected by a 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, 4 etc., are the classic examples in ani-
mal evolution, and to this day nearly the only ones ! Bate-
son s 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



33



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 Schopfungstheorie," took
positive ground against the adequacy or actuality
^ na * ura ^ selection as a species-forming factor,
and proposed a theory of "heterogene Ersen-
gimg" (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
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, Ball, 7 in a paper written in

1877, expresses his conviction that sudden changes of

species-forming character do occur, and as-

inSngpl! Crit>eS SUCh Chan & es " to the action of the

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



33 2



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
Gallon's belief by minute steps but that decisive sudden changes
steps. f 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 fixity de-
pends upon which of these sides it may be resting on, ex-
presses well the basic idea in heterogenesis or mutation by
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, 10 in his suggestive paper called "Gedanken zur
Descendenz- und Vererbungstheorie," expresses his belief
in the importance in species-forming of what he calls "pri-



OTHER THEORIES OF SPECIES-FORMING. 333

mary variations," which are large and sudden as contrasted
with "secondary variations," which are the usual small,

Emer 's the- fl uctuatm g or so-called Darwinian variations.
ory of "primary Emery bases his belief on the few cases like
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,

Korschinsk 's mucn more nearly anticipates de Vries's muta-
. theory of hetero- tion theory. Indeed this biologist, the Russian
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 ll in German which
are of the nature of vorlailfige 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



334



DARWINISM TO-DAY.



the two theories is graphically shown. 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-



Online LibraryVernon L. (Vernon Lyman) KelloggDarwinism to-day; a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxilary and alternative theories of species-forming → online text (page 31 of 38)