260 
SEXUAL selection: mammals. 
Part IL 
With quadrupeds, when, as is often the case, the 
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 Australia, 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 {Callorliinus ursinus), 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, partly 
through sexual selection, owing to a long series of vic- 
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 those of any 
other breed (though blood -hounds differ consider- 
ably), or than in any wild canine species known to me. 
See the very interesting paper by Mr. J. A. Allen in ‘Bull. Miis.. 
Comp. Zoolog. of Cambridge; United States,’ vol.ii. No. 1, p. 82. The- 
weights were ascertained by a careful observer, Capt. Bryant. 
‘ Animal Economy, p. 45.. 
