28 ON THE ORIGIN OF SPECIES 



Dipsacus ; and this amount of change may have sucL 

 denly 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 very different ways ; when 

 we compare the game-cock, so pertinacious in battle, 

 with other breeds so little quarrelsome, with ' ever- 

 lasting 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 perfect and as useful as 

 we now see them ; indeed, in several 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 

 directions useful to him. In this sense he may be said 

 to make for himself useful breeds. 



The great power of this principle of selection is not 

 hypothetical. It is certain that several of our eminent 

 breeders have, even within a single lifetime, modified 

 to a large extent some breeds of cattle and sheep. In 

 order fully to realise what they have done, it is 

 almost necessary to read several of the many treatises 

 devoted to this subject, and to inspect the animals. 

 Breeders habitually speak of an animal's organisation 

 as something quite plastic, which they can model 

 almost as they please. If I had space I could quote 

 numerous passages to this effect from highly com- 

 petent authorities. Youatt, who was probably better 

 acquainted with the works of agriculturists than 

 almost any other individual, and who was himself a 



