CHAPTER III 

 THE METHOD OF EVOLUTION' 



No one today doubts the reality of evolution, at least 

 no one does who has had practical experience in animal or 

 plant breeding, and who has seen new forms of life come 

 into being under his own observation and guidance. But 

 the method of evolution is still in doubt. It is known in 

 general, that like begets like, but that occasionally it begets 

 unlike, and this may become a new race. As to how the 

 new race is begotten we have not got much beyond Darwin ; 

 indeed many of us have not got so far. For Darwin recog- 

 nized two distinct ways in which new races may arise, but 

 many biologists today insist that there is only one way, 

 the way in which Minerva was begotten, who "sprang 

 full-fledged from the head of Jove." The modern name 

 for this method of origin is mutation, and its advocates, 

 like the "followers of the prophet," insist that there is no 

 other. 



Darwin was well aware that new races may arise in this 

 way, particularly under domestication, as in the case of 

 the Ancon ram and Niata cattle; but he believed that a 

 far commoner and more important method, particularly 

 among wild species, consists in a slow and gradual modi- 

 fication of the race, constantly in one direction, as under 

 the ever-growing power of a hydraulic press, until the 



' In these two chapters, especially in the second (chap, iv), material has been 

 drawn freely from the writer's book on Heredity in Relation to Evolution and Animal 

 Breeding (D. Appleton & Co., Xew York), for which he has the kind permission 

 of the publishers. He also wishes to acknowledge aid gi\-en by the Carnegie 

 Institution to the investigations herein described. 



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