498 THE DESCEl'IT OF MAN. 



which the females are hornless. With many animals the canine 

 teeth in the upper or lower jaw, 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 together; 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 op- 

 posite side of the head in the male consists of a rudiment about 

 ten inches in length, v/hich is embedded in the jaw; but some- 

 times, 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 

 provided with a remarkable apparatus, namely a spur on the fore- 

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

 according to Harting, the secretion from the gland is not poison- 

 ous 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 fe- 

 males 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 

 purposes, more especially as a defense against their enemies, it 



• Mr. Lamont ('Seasons with the Sea-Horses,' 1861, p. 143) says that 

 a good tusk of the male walrus weighs i pounds, and is longer than 

 that of the female, which weighs about 3 pounds. The males are 

 described as fighting ferociously. On the occasional absence of the 

 tusks in the female, see Mr. R. Brown, 'Proc. Zool. Soo.' 1868, p. 429. 



^ Owen, 'Anatomy of Vetebrates,' vol. iii. p. 283. 



" Mr. R. Brown, in 'Proc. Zool. Soc' 1869, p. 553. See Prof. Turner 

 in Journal of 'Anat. and Phys.' 1872, p. 76, on the homological nature o 

 these tusks. Also Mr. J. W. Clarke on two tusks being developed i. 

 the males in 'Proc. Zoolog. Soc' 1871, p. 42. 



■J Owen on the cachalot and Ornithorhynchus, ibid. vol. iii. pp. 638, 

 641. Harting is quoted by Dr. Zouteveen in the Dutch translat. of 

 this work, vol. ii. p. 292. 



