THE SEXES AND SEXUAL SELECTION. 



Among mammals, which stand in so many ways in marked 

 contrast to birds, the law of battle much more than the power of 

 charming decides the problem of courtship. Thus most of the strik- 

 ing secondary characters of male mammals are weapons. Yet there 

 are crests and tufts of hair, and other acknowledgments of the beauty- 

 test, while the incense of odoriferous glands is a frequent means of 

 sexual attraction. The colors, too, of the males are often more 

 sharply contrasted, and there are minor differences, in voice and the 

 like, which can not be ignored. Of weapons, the larger canine teeth 

 of many male animals, such as boars; the special tusks of, for instance, 

 the elephant and narwhal; 



j. — The development of antlers in the successive years 

 of a stag's life, or in the general history of stags. 

 From Carus Sterne. 



the antlers of stags, all but 

 exclusively restricted to the 

 combative sex; the horns of 

 antelopes, goats and sheep, 

 oxen and the like, — which 

 at least predominate in the 

 males, — are well known 

 illustrations. The manes 

 of male lions, bisons, and FlG 

 baboons, the beards of cer- 

 tain goats, the crests along 

 the backs of some antelopes, the dewlaps of bulls, — illustrate another 

 set of secondary characters. The odoriferous glands of many mammals 

 are more developed in the males, and become -specially functional 

 during the breeding season. This is well illustrated in the case of 

 goats, deer, shrew-mice, elephants. The differences in color are 

 slight compared with those seen between the sexes in birds, but in 

 not a few orders the distinction is marked enough, — males being, in 

 the great majority of cases, the more strongly and brilliantly colored. 

 Among monkeys the difference in color in the bare regions, and the 

 subtler decorations in the arrangement of the hair on the face, are 

 often very conspicuous. 



III. Darwin's Explanation. — Sexual Selection. — Darwin 

 started from the occurrence of such variations, in structure and habit, 

 as might be useful either for attraction between the sexes or in the 

 direct contests of rival males. The possessers of these variations 

 succeeded better than their neighbors in the art of courtship; the 

 factors which constituted success were transmitted to the offspring; 

 and, gradually, the variations were established and enhanced as second- 

 ary sexual characters of the species. The process by which the 

 possessers of the fortunate excellencies of beauty and strength outbid 



