CHAP. VII.] THEORY OF NATURAL SELECTION. 165 



with care Mr. Mivart's book, and comparing each section with 

 what I have said on the same head, I never before felt so strongly 

 convinced of the general truth of the conclusions here arrived at, 

 subject, of course, in so intricate a subject, to much partial error. 



All Mr. Mivart's objections will be, or have been, considered in 

 the present volume. The one new point which appears to have 

 struck many readers is, " that natural selection is incompetent to 

 account for the incipient stages of useful structures." This subject 

 is intimately connected with that of the gradation of characters, 

 often accompanied by a change of function, for instance, the 

 conversion of a swim-bladder into lungs, points which were 

 discussed in the last chapter under two headings. Nevertheless, 

 I will here consider in some detail several of the cases advanced 

 by Mr. 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 preserving 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, tkc., 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. Mivart'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 preserving 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 differences, 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 probable habits of life ; for those individuals 

 which had some one part or several wrts of their bodies rather 



