Chap. YIL] THEOEY OF NATURAL SELECTION. 277 



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 indi- 

 viduals 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 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 same manner ; whilst the 

 individuals, less favoured in the same respects, will have 

 been the most liable to perish. 



We here see that there is no need to separate single 

 pairs, as man does, when he methodically improves a 

 breed : natural selection will preserve and thus separate 

 all the superior individuals, allowing them freely to inter- 

 cross, and will destroy all the inferior individuals. By 

 this process long-continued, which exactly corresponds 

 with what I have called unconscious selection by man, 

 combined no doubt in a most important manner with 



