SEXUAL SELECTION- 69T 



female, yet in the larger size of his body, larger caaino 

 teeth, more developed whiskers, more prominent supercili- 

 ary ridges, he follows the common rule of the male excelling 

 the female. 



I have now given all the cases known to me of a differ- 

 ence in color between the sexes of mammals. Some of these 

 may be the result of variations confined to one sex and trans- 

 mitted to the same sex, without any good being gained, and 

 therefore without the aid of selection. We have instances 

 of this with our domesticated animals, as in the males of 

 certain cats being rusty red, while the females are tortoise- 

 shell colored. Analogous cases occur in nature: Mr. Bart- 

 lett has seen many black varieties of the jaguar, leopard, 

 vulpine phalanger, and wombat; and he is certain that all, 

 or nearly all, these animals were males. On the other hand, 

 with wolves, foxes, and apparently American squirrels, both 

 sexes are occasionally born black. Hence it is quite possi- 

 ble that with some mammals a difference in color between 

 the sexes, especially when this is congenital, may simply be 

 the result, without the aid of selection, of the occurrence 

 of one or more variations which from the first were sexually 

 limited in their transmission. Nevertheless it is improbable 

 that the diversified, vivid, and contrasted colors of certain 

 quadrupeds, for instance, of the above monkeys and ante- 

 lopes, can thus be accounted for. We should bear in mind 

 that these colors do not appear in the male at birth, but only 

 at or near maturity; and that, unlike ordinary variations, 

 they are lost if the male be emasculated. It is on the whole 

 probable that the strongly marked colors and other orna- 

 mental characters of male quadrupeds are beneficial to them 

 in their rivalry with other males, and have consequently 

 been acquired through sexual selection. This view is 

 strengthened by the differences in color between the sexes 

 occurring almost exclusively, as may be collected from the 

 previous details, in those groups and sub-groups of mam- 

 mals which present other and strongly marked second- 



