The Descent of Man and Selection in Relation to Sex, Vol. IDarwin, Charles
Science
The Descent of Man and Selection in Relation to Sex, Vol. I
Darwin, Charles
Evolution (Biology); Human beings -- Origin; Sex differences; Sexual dimorphism (Animals); Sexual selection in animals
on this latter point, I may add, that Mr. Powys found in Corfu
and Epirus the sexes of the chaffinch keeping apart, and “the
females by far the most numerous;” whilst in Palestine Mr.
Tristram found “the male flocks appearing greatly to exceed the
female in number.”[384] So again with the _Quiscalus major_,
Mr. G. Taylor[385] says, that in Florida there were “very few
females in proportion to the males,” whilst in Honduras the
proportion was the other way, the species there having the
character of a polygamist.
FISH.
With Fish the proportional numbers of the sexes can be
ascertained only by catching them in the adult or nearly adult
state; and there are many difficulties in arriving at any just
conclusion.[386] Infertile females might readily be mistaken
for males, as Dr. Günther has remarked to me in regard to
trout. With some species the males are believed to die soon
after fertilising the ova. With many species the males are of
much smaller size than the females, so that a large number of
males would escape from the same net by which the females were
caught. M. Carbonnier,[387] who has especially attended to the
natural history of the pike (_Esox lucius_) states that many
males, owing to their small size, are devoured by the larger
females; and he believes that the males of almost all fish are
exposed from the same cause to greater danger than the females.
Nevertheless in the few cases in which the proportional numbers
have been actually observed, the males appear to be largely in
excess. Thus Mr. R. Buist, the superintendent of the
Stormontfield experiments, says that in 1865, out of 70 salmon
first landed for the purpose of obtaining the ova, upwards of
60 were males. In 1867 he again “calls attention to the vast
disproportion of the males to the females. We had at the outset
at least ten males to one female.” Afterwards sufficient
females for obtaining ova were procured. He adds, “from the
great proportion of the males, they are constantly fighting and
tearing each other on the spawning-beds.”[388] This
disproportion, no doubt, can be accounted for in part, but
whether wholly is very doubtful, by the males ascending the
rivers before the females. Mr. F. Buckland remarks in regard to
trout, that “it is a curious fact that the males preponderate
very largely in number over the females. It _invariably_
happens that when the first rush of fish is made to the net,
there will be at least seven or eight males to one female found
captive. I cannot quite account for this; either the males are
more numerous than the females, or the latter seek safety by
concealment rather than flight.” He then adds, that by
carefully searching the banks, sufficient females for obtaining
ova can be found.[389] Mr. H. Lee informs me that out of 212
trout, taken for this purpose in Lord Portsmouth’s park, 150
were males and 62 females.
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