588 TEE DESCENT OF MAN. 



cost of retarded flight, and other ornaments at the cost ol 

 some loss of power in their battles with rival male?. 



With mammals, when, as is often the case, the sexes 

 differ in size, the males are almost always larger and 

 stronger. 1 am informed by Mr. Gould that this holds 

 good 'in a marked manner with the marsupials 01 Aus- 

 tralia, the males of which appear to continue growing 

 until an unusually late age. But the most extraordinay, 

 case is that of one of the seals (CallorhiiiKs 9rr**r* 

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

 grown male.* Dr. Gill remarks that it is with the polyg- 

 amous seals, the m;iles of which are well known to fight 

 savagely together, that the sexes differ much in size; the 

 monogamous species differing but little. Whales also 

 afford evidence of the relation existing between the pug- 

 nacity of the males and theii large size compared with that 

 ot the females; the males of the right-whales do not fight 

 togethei, and they arc not larger, but 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 sixc of the females. The greater strength of 

 the male, as Hunter long ago remarked, f is invariably dis- 

 played 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 victo- 

 ries, 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 quadru- 

 peds have acquired these characteristic cualities, occurred 

 rather late in life, arid were consequently to a large extent 

 limited in their transmission to the same sex. 



* See the very interesting paper by Mr. J. A. Allen in "Bull. Mus. 

 Coinp. Zoning, of Cambridge, United States," vol. ii, No. 1, p. 82, 

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

 Dr. Gill in "The American Naturalist," Jan., 1871: Prof. Shaler on 

 the relative size of the sexes of whales, * k American .Naturalist," 

 Jan. 1873. 



f " Animal Economy," p. 45 



