SEXUAL SELECTION 691 



times differ considerably in color, and they present, as we 

 have already seen, other remarkable sexual differences. 

 Thus the male of the Otaria nigrescens of the southern 

 hemisphere is of a rich brown shade above; while the 

 female, who acquires her adult tints earlier in life than 

 the male, is dark gray above, the young of both sexes 

 being of a deep chocolate color. The male of the north- 

 ern Phoca groenlandica is tawny gray, with a curious 

 saddle-shaped dark mark on the back; the female is much 

 smaller, and has a very different appearance, being "dull 

 white or yellowish straw-color, with a 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 protection." " 



With Euminants sexual differences of color occur more 

 commonly than in any other order. A difference of this 

 kind is general in the Strepsicerene antelopes; thus the 

 male nilghau {Portax 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 devel- 

 oped in the male than in the hornless female. I am in- 

 formed by Mr. Blyth that the male, without shedding his 

 hair, periodically becomes darker during the breeding sea- 

 son. Young males cannot be distinguished from young 

 females until about twelve months old; and if the male is 

 emasculated before this period, he never, according to the 

 same authority, changes color. The importance of this 

 latter fact, as evidence that the coloring of the Portax is 

 of sexual origin, becomes obvious, when we hear" that 

 neither the red summer-coat nor the blue winter-coat of 



ss Dr. Murie on the Otaria, "Proo. Zool. Soc," 1869, p. 108. Mr. B. 

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

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



*» Judge Oaton, in "Transactions of the Ottawa Academy of Natural 

 Sciences, " 1868, p. 4, , 



