Chap. XVIII. Mammals — Ornamental Colours. 533 



sheep, is a true secondary sexual character, for, as I hear from 

 Mr. Winwood Reade, it is not developed if the animal be 

 castrated. Although we ought to be extremely cautious, as 

 shewn in my work on ' Variation under Domestication,' in 

 concluding that any character, even with animals kept by 

 Bemi-civilised people, has not been subjected to selection by 

 man, and thus augmented, yet in the cases just specified this is 

 improbable; more especially as the characters are confined to 

 the males, or are more strongly developed in them than in the 

 females. If it were positively 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, &c, 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 

 analogous 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 Ammotragus, 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 

 purpose. With those antelopes in which the adult male is more 

 strongly-coloured than the female, and with those monkeys in 

 which the hair on the face is elegantly arranged and coloured 

 in a diversified 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. 



Colour of the Hair and of the Naked Skin.— I will first give 

 briefly all the cases known to me, of male quadrupeds differing 

 in colour from the females. With Marsupials, 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 Didelphis opossum of Cayenne 



cnap. xx. on the practice of selection logue,' ibid. p. 157. 



by semi-civilised people. For the l9 Osphranter rufu*, Gould, ' Mam- 



Berbura goat, se« Dr. Gray, ' Cata- mals of Australia,' 1863, vol. a 



