THE METHOD 91 



Now, if by the mutation theory of De Vries, any one 

 or more of these causes of variation, produces suddenly a 

 sufficient variation to establish per saltum a new species, 

 its perpetuation will depend upon its adaptation to its 

 environment, and this is the process of natural selection. 

 It is probable that some species of vegetables are sud- 

 denly formed by one jump. But is it not more probable 

 that Darwin is correct that most species, in the natural 

 state, have been formed by the survival of slow minute 

 hereditary variations upon which the principle of natural 

 selection could operate. 



The difference between the theory of Darwin and De 

 Vries, is not that between evolution, and special crea- 

 tion. Both believe in the evolution of species. De 

 Vries transfers "natural selection" from the evolution 

 of species, to the preservation of it. Either theory is 

 in accordance with the thesis of this book. It is held 

 by De Vries, that every few years variations appear, 

 as if there is an inherency of such tendency, and that 

 when these variations do come they are the new species. 



It would be exceedingly interesting to follow 

 De Vries further in his exposition of his mutation 

 theory, but space will not permit. He does say this, 

 however, "The origin of new species, which is in part 

 the effect of mutability, is, however, due mainly to 

 natural selection." It is probable that the method of 

 natural selection is the most important, if not the only 

 method, by which the great variety of species, now 

 occupying the land and water, have come about. Of 

 course, variations, whether inherent, or brought about 

 by external causes and heredity, are essential factors 

 with natural selection in the evolution of new species. 



But the causes of variation must not be identified 

 with natural selection. The latter follow the former,. 



