Chap. XVIII. 
ORNAMENTAL COLOURS. 
295 
sexually limited in their transmission. Nevertheless 
it can hardly he admitted that the diversified, vivid, 
and contrasted colours of certain quadrupeds, for in- 
stance of the above-mentioned monkeys and antelopes, 
can thus be accounted for. We should bear in mind 
that these colours do not appear in the male at birth, 
as in the case of most ordinary variations, but only at 
or near maturity ; and that unlike ordinary variations, 
if the male be emasculated, they never appear or sub- 
sequently disappear. It is on the whole a much more 
probable conclusion that the strongly-marked colours 
and other ornamental characters of male quadrupeds 
are beneficial to them in their rivalry with other males, 
and have consequently been acquired through sexual 
selection. The probability of this view is strengthened 
by the differences in colour between the sexes occur- 
ring almost exclusively, as may be observed by going 
through the previous details, in those groups and sub- 
groups of mammals, which present other and distinct 
secondary sexual characters ; these being likewise due 
to the action of sexual selection. 
Quadrupeds manifestly take notice of colour. Sir 
S. Baker repeatedly observed that the African elephant 
and rhinoceros attacked with special fury white or grey 
horses. I have elsewhere shewn that half- wild horses 
apparently prefer pairing with those of the same colour, 
and that herds of fallow-deer of a different colour, though 
living together, have long kept distinct. It is a more 
significant fact that a female zebra would not admit the 
addresses of a male ass until he was painted so as to 
resemble a zebra, and then, as John Hunter remarks, 
she received him very readily. In this curious fact, 
32 « The Variation of Animals and Plants under Domestication,’ 1868, 
¥ol. ii. p. 102, 103. 
