The Descent of Man

In the Indian black-buck (A. bezoartica), which
belongs to another tribe of antelopes, the male
is very dark, almost black; whilst the hornless
female is fawn-coloured. We meet in this species,
as Mr. Blyth informs me, with an exactly
similar series of facts, as in the Portax picta,
namely, in the male periodically changing colour
during the breeding-season, in the effects
of emasculation on this change, and in the
young of both sexes being indistinguishable
from each other. In the Antilope niger the male
is black, the female, as well as the young of
both sexes, being brown; in A. sing-sing the
male is much brighter coloured than the hornless
female, and his chest and belly are blacker;
in the male A. caama, the marks and lines
which occur on various parts of the body are
black, instead of brown as in the female; in the
brindled gnu (A. gorgon) "the colours of the
male are nearly the same as those of the female,
only deeper and of a brighter hue." (26. On the
Ant. niger, see 'Proc. Zool. Soc.' 1850, p. 133.