98 Evolution and Adaptation 



of the wild Dipsacus ; and this amount of change may have 

 suddenly arisen in a seedling. So it has probably been with 

 the turnspit dog; and this is known to have been the case 

 with the ancon sheep. But when we compare the dray- 

 horse and race-horse, the dromedary and camel, the various 

 breeds of sheep fitted either for cultivated land or mountain 

 pasture, with the wool of one breed good for one purpose, 

 and that of another breed for another purpose; when we 

 compare the many breeds of dogs, each good for man in 

 different ways ; when we compare the game-cock, so pertina- 

 cious in battle, with other breeds so little quarrelsome, with 

 ' everlasting layers ' which never desire to sit, and with the 

 bantam so small and elegant ; when we compare the host 

 of agricultural, culinary, orchard, and flower-garden races 

 of plants, most useful to man at different seasons and for 

 different purposes, or so beautiful in his eyes, we must, I 

 think, look further than to mere variability. We cannot 

 suppose that all the breeds were suddenly produced as per- 

 fect and as useful as we now see them ; indeed, in many 

 cases, we know that this has not been their history. The 

 key is man's power of accumulative selection : nature gives 

 successive variations ; man adds them up in certain direc- 

 tions useful to him. In this sense he may be said to have 

 made for himself useful breeds." 



Darwin also gives the following striking examples, which 

 make probable the view that domestic forms have really 

 been made by man selecting those variations that are useful 

 to him : — 



" In regard to plants, there is another means of observing 

 the accumulated effects of selection — namely, by comparing 

 the diversity of flowers in the different varieties of the same 

 species in the flower-garden ; the diversity of leaves, pods, 

 01 tubers, or whatever part is valued, in the kitchen-garden, 

 in comparison with the flowers of the same varieties ; and 

 the diversity of fruit of the same species in the orchard, in 



