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THE AMERICAN NATURALIST [Vol. XLIII 



versal process. Zoologists, it would seem, incline to 

 look with greater favor upon mutation as the regular 

 method of origin. 



At long intervals of time, out of millions of individuals reared in the 

 same country and fed on nearly the same food deviations of structure, 

 so strongly pronounced as to deserve to be called monstrosities, arise; 

 but monstrosities cannot be separated by any distinct line from slighter 

 variations. All such changes of structure, whether extremely slight or 

 strongly marked, which appear amongst many individuals, living to- 

 gether, may be considered as the indefinite effects of the conditions of 

 life on each individual organism. 21 



Some naturalists have maintained that all variations are connected 

 with the act of sexual reproduction, but this is certainly an error: for 

 I have given in another work a long list of " sporting plants," plants 

 which have suddenly produced a single bud with a new and sometimes 

 widely different character. 22 



Some variations useful to man have probably arisen suddenly, or 

 by one step. 23 



No one supposes that our choicest productions have been produced 

 by a single variation from one stock. 24 



It may be doubted whether sudden and considerable deviations of 

 structure such as are occasionally seen in our domestic productions, 

 more especially with plants, are ever permanently propagated in a state 

 of nature. 25 



I saw also that the preservation in a state of nature of any occasional 



and that if first preserved, it would generally be lost by subsequent 

 intercrossing with ordinary individuals. 2 * 



Adaptation 



Darwin recognized the three fundamental methods of 

 origin in nature, namely, variation, mutation and adapta- 

 tion. It seems probable that to mutation he assigned its 

 approximate value. In the ' 'Origin of Species," varia- 

 tion with selection was given the preeminent place, and 

 adaptation a minor one. Later, adaptation assumed 

 greater importance to his mind, and there is some evi- 

 dence that he may have assigned to it a value greater than 

 that of variation. He had come to see more clearly that 

 natural selection operated upon things already produced, 



