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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 22 of 38)
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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 is, 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.

8 Baldwin, J. Mark,_ "A New Factor in Evolution," Amer. Nat.,
Vol. XXX, pp. 441 ff., 1896; see also the same author's "Develop-

Referencesto ment a "d Evolution," chap, viii, 1902; in the appen-
discrassions of dices of this book is given a detailed history of the
orthopiasy. independent formulation of the theory of "Organic

Selection or Orthopiasy," by Baldwin, Osborn. and Morgan.

8 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."

10 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 :

"i. 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 (i) that where adaptive variation v
is similar in direction to individual modification m, the organism



OTHER THEORIES OF SPECIES-FORMING. 231

lias 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.

"g. 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.

"10. 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
theTktion 6 f some the species-forming influence of isolation
factor in species- i s held to be as effective as selection itself,

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 brilliant upholders and expositors of Darwin-
ism, says: 2 "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



2 3 4 DARWINISM TO-DAY.

by some authors to name the same condition), li, in a

species, a number of individuals show a certain congenital

variation, this variation will probably be lost by

What is meant crO ss-breeding with individuals not having it,

by isolation.

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,

Various means an( ^ tne ^ so ^ at ^ on mav ^ e variously named ac-
of effecting iso- cordingly. Undoubtedly the most important of

lation. these kinds of i so l at i on> at l east j n 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
miscellaneous inter-breeding. The real founder
theory of species- and most insistent upholder of the theory of
grohb hoktion. 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



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: 4 "Um den
Unterschied beider Theorien moglichst kurz auszudriicken :
nach der Darwin'schen Selectionstheorie zuchtet die Natur
in Folge des Kampfes ums Dasein rastlos neue typische
Formen der Organismen durch Auslese nutzlicher 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 langen
Zeitraumes vollziehen.

"Nach der Separationstheorie zuchtet die Natur nur
periodisch neue Formen stets ausserhalb des Wohngebietes
der Stammart durch geographische Isolierung und Kolo-
nienbildung, ohne welche bei alien hoheren 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 raumliche 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 :

"i. Jede dauernde raumliche 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 Difife-
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 Varietal oder Art entsteht ohne
Ausscheidung einzelner oder weniger Individuen von der
Stammart und ohne Ansiedelung an einem neuen Standort,
well Massenkreuzung und Gleichheit der Lebensbedin-
gungen in einem zusammenhangenden Wohngebiet immer
absorbierend und nivellierend wirken miissen und indivi-
duelle Variationen stets wieder in die Stammform zuriick-
drangen."

Wagner's 6 long series of interesting papers and addresses
are crammed with facts of plant and animal geography,
taxonomy and palaeontology, 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 T
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 (rdumliche Sonderung) was a factor

Jordan on

geographic or condition in the formation of every species,
isolation. race> Qr ^-JL^ Q an i ma i 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 faunae,
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. 23^

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-
, vidu^ls 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-
Effects of cerning the distribution and species distinction
isolation in the of the Mallophaga, a group of small wingless
allophaga. insect paras i tes on birds and mamma i s> 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-



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



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 22 of 38)