The Descent of Man

nished with special weapons for fighting with
their rivals. They possess organs which are
used during the breeding-season for producing
vocal and instrumental music. They are frequently
ornamented with combs, horns, wattles
and plumes of the most diversified kinds, and
are decorated with beautiful colours, all evidently
for the sake of display. We shall find
that, as with insects, both sexes in certain
groups are equally beautiful, and are equally
provided with ornaments which are usually
confined to the male sex. In other groups both
sexes are equally plain-coloured and unornamented.
Lastly, in some few anomalous cases,
the females are more beautiful than the males.
We shall often find, in the same group of birds,
every gradation from no difference between the
sexes, to an extreme difference. We shall see
that female birds, like female insects, often possess
more or less plain traces or rudiments of
characters which properly belong to the males
and are of use only to them. The analogy, inde-