5 54 The Descent of Man. Part IT. 



is doubtful, for the vocal organs of the males must have been 

 strengthened by use during maturity, under the powerful excite- 

 ments of love, jealousy or rage, and will consequently have been 

 transmitted to the same sex. Various crests, tufts, and mantles 

 of hair, which are either confined to the male, or are more 

 developed in this sex than in the female, seem in most cases to be 

 merely ornamental, though they sometimes serve as a defence 

 against rival males. There is even reason to suspect that the 

 branching horns of stags, and the elegant horns of certain ante- 

 lopes, though properly serving as weapons of offence or defence, 

 have been partly modified for ornament. 



When the male differs in colour from the female, he generally 

 exhibits darker and more strongly-contrasted tints. We do not 

 in this class meet with the splendid red, blue, yellow, and green 

 tints, so common with male birds and many other animals. The 

 naked parts, however, of certain Quadrumana must be excepted ; 

 for such parts, often oddly situated, are brilliantly coloured 

 in some species. The colours of the male in other cases may be 

 due to simple variation, without the aid of selection. But when 

 the colours are diversified and strongly pronounced, when they 

 are not developed until near maturity, and when they are lost 

 after emasculation, we can hardly avoid the conclusion that 

 they have been acquired through sexual selection for the sake of 

 ornament, and have been transmitted exclusively, or almost 

 exclusively, to the same sex. When both sexes are coloured in 

 the same manner, and the colours are conspicuous or curiously 

 arranged, without being of the least apparent use as a protection, 

 and especially when they are associated with various other orna- 

 mental appendages, we are led by analogy to the same conclusion 

 namely, that they have been acquired through sexual selection 

 although transmitted to both sexes. That conspicuous and 

 diversified colours, whether confined to the males or common tc 

 both sexes, are as a general rule associated in the same groups 

 and sub-groups with other secondary sexual characters serving 

 for war or for ornament, will be found to hold good, if we look 

 back to the various cases given in this and the last chapter. 



The law of the equal transmission of characters to both sexes. 

 as far as colour and other ornaments are concerned, has prevailed 

 far more extensively with mammals than with birds; but 

 weapons, such as horns and tusks, have often been transmitted 

 either exclusively or much more perfectly to the males than to the 

 females. This is surprising, for, as the males generally use theii 

 weapons for defence against enemies of all kinds, their weapons 

 would have been of service to the females. As far as we can see. 

 their absence in this sex can be accounted for only by the 



