MAMMALS. 611 



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 northern 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 yel- 

 lowish straw-color, with a tawny hue on the back;" the 

 young at first are pure white, and can " hardly be dis- 

 tinguished among the icy hummocks and snow, their color 

 thus acting as a protection."* 



With ruminants 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 jncta) is bluish-grey 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 tuft of hair are likewise more devel- 

 oped in the male than in the hornless females. I am 

 informed by Mr. Blyth that the male, without shedding 

 his hair, periodically becomes darker during the breeding- 

 season. 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 hearf 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 Tregelaphus the males are 

 darker than the hornless females, and their crests of hair are 

 more fully developed. In the male of that magnificent ante- 

 lope, the Derbyan eland, the body is redder, the whole neck 

 much blacker and the white band which separates these 

 colors broader than in the female. In the Cape eland, also, 

 the male is slightly darker than the female. | 



*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, Desniarest, ibid, pp. 243, 249. 



f Judge Caton, in "Trans. Ottawa Acad, of Nat. Sciences," 1868, 

 p. 4. 



XDt. Gray, "Cat. of Mamm. in Brit. Mas.," part iii, 1852, pp. 

 134-142; also Dr. Gray, "Gleanings from the Menagerie of Knows- 



