40 THE EVOLUTION THEORY 



unaltered. Thus it is with one of the few domesticated insects, the 

 silk-moth. Only the cocoon is of use to man, and according to the 

 cocoon different breeds are distinguished, differing in fineness, colour, 

 &c. ; but no breeds can be distinguished in reference to the larvae, or 

 the perfect insects. Among gooseberries there are about a hundred 

 varieties distinguished according to the form, colour, size, thickness 

 of skin, hairiness, &c, of the fruits, but the little, inconspicuous, 

 green blossoms, of which the breeders take no account, are alike in 

 them all. In the pansies (Viola tricolor), on the other hand, it is 

 only by the flowers that the varieties are distinguished, while the 

 seeds have remained alike in all. 



It may be asked how it could have occurred to any one, when 

 pigeons, for instance, first began to be domesticated, to wish to 

 produce fantails or pouters, since he could have no mental picture 

 of them in advance. Darwin replies to this objection, that it was not 

 always conscious and methodical artificial selection, such as is now 

 practised, that brought about the origin of breeds, but that they have 

 very often resulted, and at first perhaps always, from unconscious 

 selection. When savages tamed a dog, they used the ' best ' of their 

 dogs for breeding, that is, they chose those which had in the highest 

 degree the qualities they valued, watchfulness, for instance, or if the 

 dog were intended for the chase, keen scent and swiftness. In this 

 way the body of the animal would be changed in a definite direction, 

 especially if rivalry helped, and if it was the ambition of each to 

 possess a dog as good as, or better than those of his tribal companions. 

 That perfectly definite changes in bodily form can thus be brought 

 about unconsciously is well illustrated by the case of a racehorse. 

 This has arisen within the last two hundred years simply because the 

 fleetest of the products of crossing between the Arab and the English 

 horse were always chosen for breeding. It could not have been 

 predicted that horses with thin neck, small head, long rump, and 

 slender legs would necessarily be the swiftest runners; but this is 

 the form which has resulted from the selection, — a very ugly, but 

 very swift horse. This unconscious selection must undoubtedly have 

 played a large part in the early stages of the evolution of the breeds 

 of our domestic animals. 



But even in the fully conscious and methodical selective breeding 

 of particular characters, the breeder rarely alters only the one his 

 attention is fixed on ; generally quite a number of other characters 

 alter apart from his intention as an inevitable accompaniment of the 

 desired variation on which attention was riveted. There are breeds 

 of rabbits whose ears hang limply down instead of standing erect, 



