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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 17 of 38)
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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

Answer to the (evolution) of a complicated organ or whole

claimed improb- r ,

ability of the body-part, or during the perfecting of a chan-

timely appear- gj ng . a d ap t a tion, the numerous necessary varia-
tions needed in tions will occur in such a successive series as



to make P ssible an harmonious correlation of
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 Papilionidae, 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
oesophagus 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



I 7 8 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 necessarv tnat one should make clear just what
in the possibility standpoint he takes on the vexed problem of
the inheritance of acquired characters. With-



oharacters. ou t 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



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 larvae 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 Zweckmassig-
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



i8o 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 10 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's dis- so tnat ^ e is evidently not satisfied with the

belief in Weis- sufficiency of the three aiding explanations

mann'a principle , , T , , . . . , .,

cfgeminal already given. I hold this germinal selection,
selection. savs pi a t e , "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,' 12
outlines in detail his theory, proposed several years before,
Weismann's tliat am P^ imix i s (bisexual parentage) is so
principle of widely prevalent in both the plant and animal
ms< 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.



DARWINISM DEFENDED. 181

'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- cogency of the objections against Darwinism
nises the weight based on the inutility of slight variations, on
tat?tefa. the 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



!8 2 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.

1 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
Bi<ra of selective selective value? Such a question it is, of course, im-
Talue. 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 : i. e., 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-

4 The tsetse-fly (Glossina sp.*), long notorious as a terrible
pest of cattle in Africa, produces its ravages by disseminating
(through biting, i. e., 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 m "ch general interest) see Radl, Em., "Uber
papers on oorre- die Bedeutung des Prinzips von der Korrelation in
der Biologic," Biol. Centralbl, Vol. XXI, pp. 401-
416, 490-496, 550-560, 605-621, looi. 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

7 Dohrn, Anton, "Der Ursprung der Wirbeltiere und das Princip
des Functionswechsel," 1875.

8 Cope, E. D., "The Energy of Evolution," Amer. Nat., Vol.
XXVIII, p. 205, 1894. I quote the following: "In considering the

Cope's proof dynamics of organic evolution, it will be convenient
that natural 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.

"(i) 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.

"(4) Finally, the characters which define the organic types, so
far as they are disclosed by palaeontology, 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 iiber Mimikry," Verh. Internet. Zool.
Cong., p. 350, 1902.

* "Origin of Species," ed. 1872, p. 65.



i86 DARWINISM TO-DAY.

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

11 Weismann, A., "Uber Germinal-Selection," Verh. Internal.
Zool. Cong., 1896.

11 Weismann, A., "Vortrage uber Descendenztheorie," 2 vols., 1902.



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 as alternative theories intended. to replace more
of other theories or less nearly entirely the selection theories,
alternative^^ anc ^ those other theories intended to serve as
selection. auxiliary and supporting theories for Darwin-

ism. Obviously these two kinds of theories l 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



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 17 of 38)