230 ORIGIN OF SPECIES 



consider in some detail several of the cases advancecl by Mt. 

 Mivart, selecting those which are the most illustrative, as 

 want of space prevents me from considering all. 



The giraffe, by its lofty stature^ much elongated neck, 

 fore legs, head and tongue, has its whole frame beautifully 

 adapted for browsing on the higher branches of trees. It can 

 thus obtain food beyond the reach of the other Ungulata or 

 hoofed animals inhabiting the same country ; and this must 

 be a great advantage to it during dearths. The Niata cattle 

 in S. America show us how small a difference in structure 

 may make, during such periods, a great difference in preserv- 

 ing an animal's life. These cattle can browse as well as 

 others on grass, but from the projection of the lower jaw 

 they cannot, during the often recurrent droughts, browse on 

 the twigs of trees, reeds, &c., to which food the common 

 cattle and horses are then driven ; so that at these times the 

 Niatas perish, if not fed by their owners. Before coming 

 to Mr, Alivart's objections, it may be well to explain once 

 again how natural selection will act in all ordinary cases. 

 Man has modified some of his animals, without necessarily 

 having attended to special points of structure, by simply pre- 

 serving and breeding from the fleetest individuals, as with 

 the race-horse and greyhound, or as with the game-cock, by 

 breeding from the victorious birds. So under nature with 

 the nascent giraffe, the individuals which were the highest 

 browsers and were able during dearths to reach even an inch 

 or two above the others, will often have been preserved; 

 for they will have roamed over the whole country in search 

 of food. That the individuals of the same species often 

 differ slightly in the relative lengths of all their parts may 

 be seen in many works of natural history, in which careful 

 measurements are given. These slight proportional differ- 

 ences, due to the laws of growth and variation, are not of the 

 slightest use or importance to most species. But it will have 

 been otherwise with the nascent giraffe, considering its prob- 

 able habits of life ; for those individuals which had some one 

 part or several parts of their bodies rather more elongated 

 than usual, would generally have survived. These will have 

 intercrossed and left offspring, either inheriting the same 

 bodily peculiarities, or with a tendency to vary again in the 



