260 SEXUAL selection: mammals. PartIL 



With quadrupeds, when, as is often the case, tlie 

 sexes differ in size, the males are, I believe, always 

 larger and stronger. This holds good in a marked 

 manner, as I am informed by Mr. Gould, with the mar- 

 supials of x\ustralia, the males of which appear to 

 continue growing until an unusually late age. But 

 the most extraordinary case is that of one of the 

 seals {Calloi^hiniis iirsinus), a full-grown female weigh- 

 ing less than one-sixth of a full-grown male.^^ The 

 greater strength of the male is invariably displayed, 

 as Hunter long ago remarked,^^ in those parts of the 

 body which are brought into action in fighting with 

 rival males, — for instance, in the massive neck of the 

 bull. Male quadrupeds are also more courageous and 

 pugnacious than the females. There can be little 

 doubt that these characters have been gained, j^artly 

 throuofh sexual selection, owinsr to a lono^ series of vie- 

 tories by the stronger and more courageous males over 

 the weaker, and partly through the inherited effects of 

 use. It is probable that the successive variations in 

 strength, size, and courage, whether due to so-called 

 spontaneous variability or to the effects of use, by the 

 accumulation of which male quadrupeds have acquired 

 these characteristic qualities, occurred rather late in 

 life, and were consequently to a large extent limited 

 in their transmission to the same sex. 



Under this point of view I was anxious to obtain 

 information in regard to the Scotch deer-hound, the 

 sexes of which differ more in size than tliose of any 

 other breed (though blood -hounds differ consider- 

 ably), or than in any wild canine species known to me. 



^"- See the very interesting jDaper by Mr. J. A. Allen in ' Bull. IMus. 

 Comp. Zoolog. of Cambridge; United States," vol. ii. No. 1, p. 82. The 

 weights were ascertained by a careful observer, Capt. Bryant. 



^2 ' Animal Economy, p. 45. 



