372 SEXUAL SELECTION: MAMMALS. [Part II. 



tion lias not been applied to these characters, then they 

 must be due to simple variability, together with sexually- 

 limited inheritance. 



In this case it would appear reasonable to extend the 

 same view to the many analogous characters occurring in 

 animals under a state of nature. Nevertheless, I cannot 

 persuade myself that this view is applicable in many- 

 cases, as in that of the extraordinary development of hair 

 on the throat and fore-legs of the male Ammotragus, or 

 of the immense beard of the male Pithecia. With those 

 antelopes in which the male when adult is more strongly 

 colored than the female, and with those monkeys in which 

 this is likewise the case, and in which the hair on the face 

 is of a different color from that on the rest of the head, 

 being arranged in the most diversified and elegant man- 

 ner, it seems probable that the crests and tufts of hair 

 have been acquired as ornaments ; and this I know is the 

 opinion of some naturalists. If this view be correct, 

 there can be little doubt that they have been acquired, or 

 at least modified, through sexual selection. 



Color of the Hair and of the Naked Skin. — I will 

 first give briefly all the cases, known to me, of male quad- 

 rupeds differing in color from the females. With Marsu- 

 pials, as I am informed by Mr. Gould, the sexes rarely 

 differ in this respect ; but the great red kangaroo offers a 

 striking exception, "delicate blue being the prevailing 

 tint in those parts of the female which in the male are 

 red." 19 In the DidelpJiis opossum of Cayenne the female 

 is said to be a little more red than the male. With Ro- 

 dents Dr. Gray remarks : " African squirrels, especially 

 those found in the tropical regions, have the fur much 

 brighter and more vivid at some seasons of the year than 



19 Ospkranler rnfus, Gould, 'Mammals of Australia,' vol. ii. 1863. 

 On the Didelphis, Desmarest ' Mammalogie,' p. 256. 



