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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 26 of 38)
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tloni the 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.
Palaeontology 8 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. The 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

Sostlectira. 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. t ' ieir 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 crvollkomnungsprihzip ,
in the organism, while ^imer finds orthogenesis produced
and controlled by the directly working external factorsVof
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 10 theory of orthogenesis depends upon the as-
sumption of his so-called principle of progressive develop-
Hfigeli's theory rnent (Verz'ollkomnungsprinsip), a something
of orthogenesis, inherent in the organic world which makes
each organism in itself a force or factor making towards



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 ll 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 organisms, 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
Another t e ^^ suc ^ e ^ ects ' re peated and intensified, re-
of orthogenetic suit in a certain degree of modification or con-
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, 14 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-
oHacts tending* stract of PIate>s " resume of the facts or
to prove ortho- phenomena which may be looked on as positive
evidence for orthogenesis (although Plate cau-
tiously notes that some of these may be only phenomena of
orthoselection). These phenomena pointing toward ortho-
genesis may be grouped into six categories :

i. 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-
Parallelisnuj in tions o f unmistakably similar character, which

variation.

often appear in different branches of the same
large group. "Comparative anatomy reveals many ex-



28o 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 (Babirnssa alfurus} ; the
&i an t norns f rnany 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 Smilodon neogaus.

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



OTHER THEORIES OF SPECIES-FORMING. 281

hen with a parrot's beak. And we can declare with con-
fidence that a chorda dorsalis can never appear in a beetle.
Constitutional Through th 6 very fact that an animal belongs
limitations on to a group the possibilities of variation are
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, 1 * 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 palaeontology seem to prove the existence
of orthogenetic evolution. "Wherever a large supply of ma-
Facts from terial permits the working out of a phyletic

palaeontology ser i e s, we always see a limited number of lines

supporting or-
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- a ^ so snow > 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
Elmer's theory Q or g an j c 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. 17 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;



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 (Entzvicklungsstillstand) ; a sudden de-
velopment by leaps, called halmatogenesis (which is almost
exactly the fundamental idea in Korschinsky's and de Vries's
later heterogenesis theory) ; and third, a hindrance or diffi-
culty in reproduction (which is the essential 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
Entivicklungsstillstand 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 th**
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
go on. 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 Entivicklungsstillstand, 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 theory is not the result of pure speculation, but is
the unavoidable conclusion 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 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 wfyo has most
Cope's ortho- definitelv formulated his beliefs into a complete

genetic theorj.

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-



2 86 DARWINISM TO-DAY.

sesthetism (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
book "The Origin of the Fittest," 1887) :

"i. 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.

"5. 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.'

"9. An attempt to account for the origin of 'mimetic
analogy' by 'maternal impressions.' "

In later writings 20 Cope subdivides his kinetogenesis prin-
ciple, or the influence of use, disuse, and environment, into
a physico-chemical influence affecting the organism through



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 26 of 38)