MAMMALS. 609 



known that the above African ram is a descendant of the 

 same primitive stock as the other breeds of sheep, and if 

 the Berbura male goat, with his mane, dewlap, etc., is 

 descended from the same stock as other goats, then, 

 assuming that selection has not been applied to these 

 characters, they must be due to simple variability, together 

 with sexually limited inheritance. 



Hence it appears reasonable to extend this same view to 

 all analagous cases with animals in a state of nature. 

 Nevertheless I cannot persuade myself that it generally 

 holds good, as in the case of the extraordinary development 

 of hair on the throat and fore legs of the male Ammo- 

 tragus, or in that of the immense beard of the male 

 Pithecia. Such study as I have been able to give to nature 

 makes me believe that parts or organs which are highly 

 developed were acquired at some period for a special pur- 

 pose. With those antelopes in which the adult male is 

 more strongly colored than the female, and with those 

 monkeys on which the hair on the face is elegantly arranged 

 and colored in a diversfied manner, it seems probable that 

 the crests and tufts of hair were gained as ornaments; and 

 this I know is the opinion of some naturalists. If this be 

 correct, there can be little doubt that they were gained or 

 at least modified through sexual selection ; but how far 

 the same view may be extended to other mammals is 

 doubtful. 



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

 give briefly all the cases known to me of male quadrupeds 

 differing in color from the females. With marsupials, as I 

 am informed by Mr. Grould, the sexes rarely differ in this 

 respect; but the great red kangaroo offers a striking excep- 

 tion, *^ delicate blue being the prevailing tint in those parts 

 of the female which in the male are red."* In the 

 Didelphis opossum of Cayenne the female is said to be a 

 little more red than the male. Of the rodents, 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 at others, and the fur of 



*08phranter rufiis, Gould, "Mammals of Australia," 1863, vol. 

 U. On the Didelphis, Desmarest, " Mammalogie," p. 35, 



