632 THE DE8CENT OF MAN, 



which the males endeavor to excite or allure the females by 

 various charms. This is probably carried on in some cases 

 by the powerful odors emitted by the males during the 

 breeding-season ; the odoriferous glands having been acquired 

 through sexual selection. Whether the same view can be 

 extended to the voice is doubtful, for the vocal organs of 

 the males must have been strengthened by use during 

 maturity, under the powerful excitements 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 defense 

 against rival males. There is even reason to suspect that 

 the branching horns of stags and the elegant horns of cer- 

 tain antelopes, though properly serving as weapons of 

 offense or defense, have been partly modified for ornament. 

 When the male differs in color from the female, he gen- 

 erally 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 maje birds and 

 many other animals. The naked parts, however, of cer- 

 tain Quadrumana must be excepted; for such parts, often 

 oddly situated, are brilliantly colored in some species. The 

 colors of the males in other cases may be due to simple 

 variation without the aid of selection. But when the colors 

 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 colored in 

 the same manner, and the colors are conspicuous or 

 curiously arranged, without being of the least apparent use 

 as a protection, and especially when they are associated 

 with various other ornamental appendages, we are led by 

 analogy to the same conclusion, namely, that they have 

 been acquired through sexual selection, although trans- 

 mitted to both sexes. That conspicuous and diversified 

 colors, whether confined to the males or common to both 

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

 and sub-groups with other secondary sexual characters serv- 

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



