Chap. VII.] THEORY OF NATURAL SELECTION. 177 



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 bave 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 con- 

 version of a swim-bladder into lungs, — points which were discussed 

 in the last chapter under two headings. Nevertheless, I will hern 

 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 ISliata cattle in S. America show us how small a 

 difference in structure may make, during such periods, a great differ- 

 ence 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, &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. 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 



