i02 The Descent of Man. Tar r II, 



antelopes in which the females are hornless. Wiih many animals 

 the canine teeth in the upper or lower juw, or in both, are much 

 larger in the males than in the females, or are absent in the 

 latter, with the exception sometimes of a hidden rudiment. 

 Certain antelopes, the musk-deer, camel, horse, boar, various 

 apes, seals, and the walrus, offer instances. In the females of 

 the walrus the tusks are sometimes quite absent.* In the male 

 elephant of India and in the male dugong" the upper incisors 

 form offensive weapons. In the male narwhal the left canine 

 alone is developed into the well-known, spirally-twisted, so- 

 called horn, which is sometimes from nine to ten feet in length. 

 It is believed that the males use these horns for fighting to- 

 gether ; for " an unbroken one can rarely be got. and occasionally 

 ■■' one may be found with the point of another jammed into the 

 " broken place."" The tooth on the opposite side of the head in 

 the male consists of a rudiment about ten inches in length, 

 which is embedded in the jaw ; but sometimes, though rarely, 

 both are equally developed on the two sides. In the female both 

 are always rudimentary. The male cachalot has a larger head 

 than that of the female, and it no doubt aids him in his 

 aquatic battles. Lastly, the adult male ornithorhynchus is pro- 

 vided with a remarkable apparatus, namely a spur on the foreleg, 

 closely resembling the poison-fang of a venomous snake ; but ac- 

 cording to Harting, the secretion from the gland is not poisonous ; 

 and on the leg of the female there is a hollow, apparently for the 

 reception of the spur.' 



When the males are provided with weapons which in the 

 females are absent, there can hardly be a doubt that these serve 

 for fighting with other males; and that they were acquired 

 through sexual selection, and were transmitted to the male sex 

 alone. It is not probable, at least in most cases, that the females 

 have been prevented from acquiring such weapons, on account 

 of their being useless, superfluous, or in some way injurious. 

 On the contrary, as they are often used by the males for various 



■* Mr. Lament ('Seasons with the ° Mr. E. Bi-own, in ' Proc. Zool. 



Sea-Horses,' 1861, p, 143) says that Soc." 1869, p. 55:3. See Prof. Turner, 



a good tusk of the male walrus in Journal of 'Anat. and Phys.' 1872, 



weighs 4 pounds, and is longer than p. 76, on the homological nature of 



that of the female, which weighs these tusks. Also Mr. J. W. Clarke 



about 3 pounds. The males are on two tusks being developed in the 



described as ligiiting ferociously, males, in ' Proc. Zjolog. Soc' 1871, 



On the occasional absence of the p. 42. 



tusks in the female, see Mr. R. ' Owen on the cachalot and 



Brown, ' Proc. Zool. Sec' 1868, p. Ornithorhynchus, ibid. vol. ill. pp. 



429. 638,641. Harting is quoted by Dr. 



' Owen, ' An.itom'- of Vertchri-tes,' Zouteveen in tha Dutch translat. of 



vol. iii. p. 283. this work, vol. ii. p. 292. 



