OBJECTIONS TO THE THEORY 303 



such periods, a great difference in preserving an ani- 

 mal's life. These cattle can browse as well p.d others 

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

 cannot, during the often recurrent droughts, browse oa 

 the twigs of trees, reeds, etc., 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 racehorse and greyhound, 

 or as with the gamecock, by breeding from the victorious 

 birds. So under nature with the nascent giraffe, the in- 

 dividuals 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 dift'er slightly 

 in the relative lengths of all their parts may be seen ia 

 many works of natural history, in which careful measure- 

 ments 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 parts of their bodies rather 

 more elongated than usual would generally have sur- 

 vived. These will have intercrossed and left offspring, 

 either inheriting the same bodily peculiarities, or with a 

 tendency to vary again in the same manner; while the 



