248 SEXUAL selection: mammals. PartIL 



rhinoceros they are said to be shorter in the female.^^ 

 From these various facts we may conclude that horns 

 of all kinds, even when they are equally developed in 

 both sexes, were primarily acquired by the males in 

 order to conquer other males, and have been trans- 

 ferred more or less completely to the female, in relation 

 to the force of the equal form of inheritance. 



The tusks of the elephant, in the different species or 

 races, differ according to sex, in nearly the same manner 

 as the horns of ruminants. In India and Malacca the 

 males alone are provided with well-developed tusks. 

 The elephant of Ceylon is considered by most na- 

 turalists as a distinct race, but by some as a distinct 

 species, and here *' not one in a hundred is found with 

 "tusks, the few that possess them being exclusively 

 " males." ^^ The African elephant is undoubtedly dis- 

 tinct, and the female has large, well-developed tusks, 

 though not so large as those of the male. These dif- 

 ferences in the tusks of the several races and species of 

 elephants — the great variability of the horns of deer, 

 as notably in the wild reindeer — the occasional pre- 

 sence of horns in the female Antilojje hezoartica — the 

 presence of two tusks in some few male narwhals — the 

 complete absence of tusks in some female walruses ; — 

 are all instances of the extreme variability of secondary 

 sexual characters, and of their extreme liability to 

 differ in closely-allied forms. 



Although tusks and horns appear in all cases to have 

 been primarily developed as sexual weapons, they often 

 serve for other purposes. The elephant uses his tusks 



^^ Sir Andrew Smith, ' Zoology of S. Africa,' pi. xix. Owen, 'Ana- 

 tomy of Vertebrates,' vol. iii. p. 624. 



^^ Sir J. Emerson Tennent, ' Ceylon,' 1859, vol. ii. p. 274. For 

 Malacca, ' Journal of Indian Archipelago,' vol. iv. p. 357. 



