oS^ 



THE DESCENT OF MAN 



diflEer in size, the males are almost always larger and 

 stronger. I am informed by Mr. Gould that this holds 

 good in a marked manner with the marsupials of Aus- 

 tralia, the males of which appear to continue growing 

 until an unasually late age. But the most extraordinary 

 case is that of one of the seals {Calhrhinus urainits), a full- 

 grown female weighing less than one-sixth of a full-grown 

 male." Dr. Gill remarks that it is with the polygamous 

 seals, the males of which are well known to fight savagely 

 together, that the sexes differ much in size; the monoga- 

 mous species differing but little. Whales also afford evi- 

 dence of the relation existing between the pugnacity of the 

 males and their large size compared with that of the female; 

 the males of the right-whales do not fight together, and 

 they are not larger, bat rather smaller, than their females; 

 on the other hand, male sperm-whales fight much together, 

 and their bodies are "often found scarred with the imprint 

 of their rival's teeth," and they are double the size of the 

 females. The greater strength of the male, as Hunter long 

 ago remarked," is invariably displayed 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 selec- 

 tion, owing to a long series of victories 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 mere variability or to the effects of use, by 

 the accumulation of which male quadrupeds have acquired 

 these characteristic qualities, occurred rather late in life, 



^ See the very interesting paper by Mr. J. A. Ailen in "Bull. Mus. Oomp. 

 Zoolog. of Cambridge, United States," vol. ii.. No. I, p. 82. The weights were 

 ascertained by a careful observer, Oapt. Bryant. Dr. Gill in "The Americaa 

 Naturalist," Jan. 1871. Prof. Shaler on the relative size of the sexes of 

 whales, "American Naturalist," Jan. 1813. 



" "Animal Economy," p. 46. 



