SEXUAL SELECTION 699 



for the sake of ornament even more brilliantly than the 

 face; but this is not more strange than that the tails of many 

 birds should be especially decorated. 



With mammals we do not at present possess any evidence 

 that the males taice pains to display their charms before the 

 female ; and the elaborate manner in which this is performed 

 by male birds and other animals is the strongest argument 

 in favor of the belief that the females admire, or are excited 

 by, the ornaments and colors displayed before them. There 

 is, however, a striking parallelism between mammals and 

 birds in all their secondary sexual characters, namely, in 

 their weapons for fighting with rival males, in their orna- 

 mental appendages, and in their colors. In both classes, 

 when the male differs from the female, the young of both 

 sexes almost always resemble each other, and in a large ma- 

 jority of cases resemble the adult female. In both classes 

 the male assumes the characters proper to his sex shortly 

 before the age of reproduction; and, if emasculated at an 

 early period, loses them. In both classes, the change of 

 color is sometimes seasonal, and the tints of the naked parts 

 sometimes become more vivid during the act of courtship. 

 In both classes the male is almost always more vividly or 

 strongly colored than the female, and is ornamented with 

 larger crests of hair or .feathers, or other such appendages. 

 In a few exceptional cases the female in both classes is more 

 highly ornamented than the male. With many mammals, 

 and at least in the case of one bird, the male is more odor- 

 iferous than the female. In both classes the voice of the 

 male is more powerful than that of the female. Considering 

 this parallelism there can be little doubt that the same cause, 

 whatever it maybe, has acted on mammals and birds; and 

 the result, as far as ornamental characters are concerned, 

 may be attributed, as it appears to me, to the long-continued 

 preference of the individuals of one sex for certain individ- 

 uals of the opposite sex, combined with their success in 

 leaving a larger number of offspring to inherit their supe- 

 rior attractions. 



