Chap. XVIII. Mammals — Ornamental Colours. 535 



female, who acquires her adult tints earlier in life than the male, 

 is dark-grey above, the young of both sexes being of a deep 

 chocolate colour. The male of the northern Pit oca groenlandicu 

 is tawny grey, 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-colour, with a 

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

 and can " hardly be distinguished among the icy hummocks and 

 " snow, their colour thus acting as a protection." 23 



With Euminants sexual differences of colour occur more 

 commonly than in any other order. A difference of this kind is 

 general in the Strepsicerene antelopes ; thus the male nilghau 

 (P&rfrjx picta) 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 

 tufts of hair are likewise more developed in the male than in the 

 hornless female. 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 colour. The importance of this latter fact, as 

 evidence that the colouring of the Portax is of sexual origiu 

 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-orna- 

 mented 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 magnificent antelope, the Derbyan eland, the 

 body is redder, the whole neck much blacker, and the white band 

 which separates these colours, broader, than in the female. In 

 the Cape eland .also, the male is slightly darker than the female. 25 



In the Indian black-buck (A. bezoartica), which belongs to 

 another tribe of antelopes, the male is very dark, almost black ; 

 whilst the hornless female is fawn-coloured. We meet in this 



23 Dr. Murie on the Otaria, ' Proc. 142; also. Dr. Gray, 'Gleaning* 

 Zool. Soc' 18G9, p. 108. Mr. R. from the Menagerie of Knowsley. 

 Brown, on the P. groenlandica, ibid, in which there is a splendid drawing 

 1868, p. 417. See also on the of the Oreas dcrbianus : see the text 

 colours of seals, Desmarest, ibid. p. on Tragelaphus. For the Cape 

 243, 249. eland (Oreas carina), see Andrew 



24 Judge Caton, in ' Trans. Ottawa Smith, ' Zoology of S. Africa,' pi. 41 

 Acad, of Nat. Sciences,' 1868, p. 4. and 42. There are also many of 



85 Dr. Gray, ' Cat. of Mnmm. in these antelopes in the Zoological 

 Brit, Mus.' part iii. 1852, pp. 134- Gardens. 



