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 12 of 38)
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development of plumage in the nuptial season by both

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

Morgan T lists twenty objections to the sexual selection

theory, several of which are identical with those already

mentioned in the foregoing paragraphs, but

Morgan's list amon g which are several to which we have not

of objections.

referred. One of these is that some of the

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


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

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

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

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


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

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

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


to the female, and in which sexual selection might be pre-
sumed to have been the influence in producing a pronounced
male type of preferred pattern, it is this

Mayer's ex- * T , . , . .

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


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

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

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

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

"It is also interesting to note that normal males pay no
attention to males with female wings.

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


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

More recently Mayer (and Soule) * repeated these experi-
ments on a more extensive scale and with some variations
in character. Fifteen hundred cocoons of

Mayer and

Soule's experi- Promethea were collected in the winter of 1901-
02 and hung in trees so that the issuing moths
might fly about unconfined. "About six hundred males
emerged from the cocoons and the wings of about one-half
of them were painted with scarlet or green ink, while the
others were allowed to remain normal in colour. It was
evident that the males whose wings were scarlet and green
succeeded fully as well in their attempts to mate as did the
normal males."

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

To these experiments may be added the observations of

Douglass, 10 who found that females of the wall-lizard,

Lacerta miiralis, showed no preference what-

Experimenti e er amon g the variable patterns exhibited by

on lizards.

males in breeding-coat. Durigen ll observed
that male lizards without tails are accepted readily by

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


tions of secondary sexual characters which various biol-
ogists have offered. These explanations will be presented
Alternative ex- in some detail in chapter xi, which is devoted
JndaryTxnll 860 " to an exposition of the various alternative
characters. theories proposed to replace or partially to re-
place the Darwinian theories. It must be sufficient to say here
that the theories proposed to account for secondary sexual
characters mostly rest on one or both of two principal basic
assumptions ; first, that the secondary sexual characters are
produced as the result of the immediate stimulus (naturally
different) of the sexually differing primary reproductive
organs, this stimulus being usually considered to result
from an internal secretion of the genital organs acting on
certain tissues of the organism ; and, second, that the males
in most species possess an excess of energy which manifests
itself in extra-growths, extra-development of pigment,
plumage, etc., and that displays by the males of special move-
ments, sound-making, etc., are direct effects or manifesta-
tions of sexual excitation. To these explanations should be
added the rather far-fetched one of Emery, who believes that
many cases of secondary sexual differences are explained by
the sudden appearance (mutation) of another form of male
or female, the persistence for a while of the two forms side
by side, as now exists in numerous dimorphic species (espe-
cially among insects), and then the gradual dying out (kill-
ing out by natural selection) of one of the two old original
forms (the one like the other sex), thus leaving the other,,
or aberrant form. The ideas of Cunningham, 12 who does
not believe that -any selection of fortuitous variation can
account for secondary sexual characters, may also be re-
ferred to. In a book of over three hundred pages this
author lists and describes according to principal animal
groups a host of secondary sexual characters, and pro-
poses a theory to account for them. "The direct effects,"
writes Cunningham, "of regularly recurrent stimulations are


sooner or later developed by heredity, but only in associa-
tion with the physiological conditions under which they were
originally produced. This is the explanation of the limita-
tions of particular modifications not merely to particular
species or kinships, but to particular periods in the life of
the individual, to a particular sex and even to a particular
season of the year in that sex." The author believes that an
examination of secondary sexual characters shows that they
develop at places and in parts which are at the time of
sexual excitement unusually directly stimulated by exertion
or contact or use. These secondary sexual characters are
"in many cases not merely limited to the period of mature
life but actually to that part of the year in which the repro-
ductive organs are active, that is to the breeding season."

In closing this chapter given up to objections to the Dar-
winian theories of natural and sexual selection, attention

may be called to Wolffs " objection to natural
Importance of selection based upon the dependence of the na-

tura l selection theory on the sexual selection

support of the theory for explanation of the existence of orna-

natural selection

theory. mental characters, and of all these secondary

sexual characters, which are useless or even
apparently disadvantageous in the life-and-death inter-
specific struggle for space and food. As Wolff looks on the
sexual selection theory as wholly discredited, he finds this
necessary dependence on it by believers in natural selection
for the explanation of those characters just mentioned
strong evidence for the weakness of the natural selection


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


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

3 Plate, L., "Uber die Bedeutung des Darwin'schen Selections-
prinzips," pp. 107-111, 2d. ed., 1903, Leipzig.

* Darwin outlined the theory of sexual selection in the "Origin
of Species" (1859), but first treated it at length in the "Descent of
Man" (Parts II and III), 1871.

4 Wallace, A. R., "Tropical Nature," chap, v, 1878 ; and "Darwin-
ism," chap, x, 1891, London.

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

a See note 2.

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

8 Mayer, A. G., "On the Mating Instinct in Moths," Psyche, Vol.
IX, pp. 15-20, 1900.

' Mayer, A. G., and Soule, C. G., "Some Reactions of Cater-
pillars and Moths," Jour. Exper. Zool., Vol. Ill, pp. 427-431, 1906.

10 Douglass, N. G., "On the Darwinian Hypothesis of Sexual
Selection," Nat. Science, Vol. VII, pp., 398-406, 1895.

11 Diirigen, "Deutschlands Amphibien u. Reptilien," p. 89, 1897.

ia Cunningham, J. T., "Sexual Dimorphism in the Animal King-
dom," 1900.

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

"An diese Falle reiht sich vielleicht am besten die Betrachtung
der Folgen, welche frtihzeitige Sterilitat auf die Ausbildung von
Wolff's exposi- se kundaren Geschlechtscharakteren ausiibt. Wir kon-
tionofweak- nen ja diese Erscheinungen auch in gewissem Sinne
nesses in sexual zu den Riickbildungen rechnen ; sie haben aber insbe-
se ion. sondere auch das mit den vorigen Fallen gemeinsam,

dass wir hier ebenfalls einen im individuellen Leben des Organismus
sich abspielenden Vorgang beobachten konnen, der nach der Selek-
tionstheorie nicht eintreten durfte.

"Nach der Selektionstheorie entstehen ja sekundare Geschlechts-


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

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

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

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


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

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

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


IN taking up the defence of Darwinism it should be noted

in the first place that the anti-Darwinians are without the

walls ; that theirs is the burden of attack ; that

pofitTof the against them is the presumption of right. The

defenders of Darwinians are m the castle, theirs simply the

Darwinism. . .' , ,

necessity of withstanding or repelling really
significant and truly threatening attack; theirs the strength
of possession and the presumption of truth. Much anti-
Darwinism is futile and easily answered; much was an-
swered by Darwin * himself before ever the anti-Darwinians
formulated it ; much other anti-Darwinism is directed against
a position which Darwinism, true Darwinism, has long seen
the inadvisability, indeed the impossibility, of holding.

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 12 of 38)