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SEXUAL SELECTION.

Inasmuch as peculiarities often appear under domestication in one sex
and become hereditarily attached to that sex, so no doubt it will be
under nature. Thus it is rendered possible for the two sexes to be
modified through natural selection in relation to different habits
of life, as is sometimes the case; or for one sex to be modified in
relation to the other sex, as commonly occurs. This leads me to say a
few words on what I have called sexual selection. This form of selection
depends, not on a struggle for existence in relation to other organic
beings or to external conditions, but on a struggle between the
individuals of one sex, generally the males, for the possession of the
other sex. The result is not death to the unsuccessful competitor, but
few or no offspring. Sexual selection is, therefore, less rigorous than
natural selection. Generally, the most vigorous males, those which are
best fitted for their places in nature, will leave most progeny. But in
many cases victory depends not so much on general vigour, but on having
special weapons, confined to the male sex. A hornless stag or spurless
cock would have a poor chance of leaving numerous offspring. Sexual
selection, by always allowing the victor to breed, might surely give
indomitable courage, length of spur, and strength to the wing to
strike in the spurred leg, in nearly the same manner as does the brutal
cockfighter by the careful selection of his best cocks. How low in the
scale of nature the law of battle descends I know not; male alligators
have been described as fighting, bellowing, and whirling round, like
Indians in a war-dance, for the possession of the females; male salmons
have been observed fighting all day long; male stag-beetles sometimes
bear wounds from the huge mandibles of other males; the males of certain
hymenopterous insects have been frequently seen by that inimitable
observer M. Fabre, fighting for a particular female who sits by, an
apparently unconcerned beholder of the struggle, and then retires
with the conqueror. The war is, perhaps, severest between the males
of polygamous animals, and these seem oftenest provided with special
weapons. The males of carnivorous animals are already well armed; though
to them and to others, special means of defence may be given through
means of sexual selection, as the mane of the lion, and the hooked jaw
to the male salmon; for the shield may be as important for victory as