he history
of the organic world. I am aware that much remains doubtful, but I have
endeavoured to give a fair view of the whole case. In the lower
divisions of the animal kingdom sexual selection seems to have done
nothing; such animals are often affixed for life to the same spot, or
have the sexes combined in the same individual, or, what is still more
important, their perceptive and intellectual faculties are not
sufficiently advanced to allow of the feelings of love and jealousy, or
of the exertion of choice. When, however, we come to the Arthropoda and
Vertebrata, even to the lowest classes in these two great sub-kingdoms,
sexual selection has effected much; and it deserves notice that we here
find the intellectual faculties developed, but in two very distinct
lines, to the highest standard, namely in the Hymenoptera [ants, bees,
etc.], among the Arthropoda [many insects, spiders, etc.], and in the
Mammalia, including man, among the Vertebrata.

In the most distinct classes of the animal kingdom--in mammals, birds,
fishes, insects and even crustaceans--the differences between the sexes
follow almost exactly the same rules. The males are almost always the
wooers; and they alone are armed with special weapons for fighting with
their rivals. They are generally stronger and larger than the females,
and are endowed with the requisite qualities of courage and pugnacity.
They are provided, either exclusively or in a much higher degree than
the females, with organs for vocal or instrumental music, and with
odoriferous glands. They are ornamented with infinitely diversified
appendages and with the most brilliant or conspicuous colors, often
arranged in elegant patterns, while the females are unadorned. When the
sexes differ in more important structures it is the male which is
provided with special sense-organs for discovering the female, with
locomotive organs for reaching her, and often with prehensile organs
for holding her. These various structures for charming or securing the
female are often developed in the male during only part of the year;
namely, the breeding season. They have in many cases been transferred in
a greater or less degree to the females; and in the latter case they
often appear in her as mere rudiments. They are lost or never gained by
the males after emasculation. Generally they are not developed in the
male during early youth, but appear a short time before the age for
reproduction. Hence, in most cas