£74 SEXUAL SELECTION: MAMMALS. [Part II, 



tawny hue on the back;" the young at first are pure 

 white, and can "hardly be distinguished among the icy 

 hummocks and snow, their color thus acting as a protec- 

 tion." 23 



With Ruminants sexual differences of color occur more 

 commonly than in any other order. A difference of this 

 kind is general with the Strepsicerene antelopes ; thus the 

 male nilghau {JPortax picta) is bluish-gray and much 

 darker than the female, with the square white patch on 

 the throat, the white marks on the fetlocks, and the black 

 spots on the ears, all much more distinct. We have seen 

 that in this species the crests and tufts of hair are likewise 

 more developed in the male than in the hornless female. 

 The male, as I am informed by Mr. Blyth, without shed- 

 ding his hair, periodically becomes darker during the 

 breeding-season. Young males cannot be distinguished 

 from young females until above twelve, months old ; and 

 if the male is emasculated before this period, he never, 

 according to the same authority, changes color. The im- 

 portance of this latter fact, as distinctive of sexual color- 

 ing, becomes obvious, when we hear 24 that neither the red 

 summer-coat nor the blue winter-coat of the Virginian deer 

 is at all affected by emasculation. With most or all of 

 the highly-ornamented species of Tragelaphus the males 

 are darker than the hornless females, and their crests of 

 hair are more fully developed. In the male of that mag- 

 nificent antelope, the Derbyan Eland^ the body is redder, 

 the whole neck much blacker, and the white band which 

 Beparates these colors, broader, than in the female. In 

 the Cape Eland also, the male is slightly darker than the 

 female. 25 



83 Dr. Murie on the Otaria, « Proc. Zool. Soc' 1869, p. 108. Mr. R. 

 Brown, on the P.' Groenlandica, ibid. 1868, p. 417. See also on the colors 

 of seals, Desmarest, ibid. pp. 243, 249. 



24 Judge Caton, in 'Trans. Ottawa Acad, of Nat. Sciences.' 1868, p. 4. 



85 Dr. Gray, ' Cat of Mamm. in Brit. Mus.' part iii. 1852, pp. 134-142 ; 



