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SEXUAL selection: mammals. 
Part 1L 
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 Antilope 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,’ toI. iii. p. 624. 
Sir J. Emerson Tennent, ‘ Ceylon,’ 1859, vol. ii. p. 274. For 
Malacca, ‘ Journal of Indian Archipelago,’ vol. iv. p. 357. 
