No. 506] DARWIN AND MUTATION THEORY 



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direction. But now we come to the conclusion of De 

 Vries which we know Darwin would not have accepted, 

 at least in its entirety. As we have seen, he was com- 

 pelled to concede that what we now call mutation had 

 occasionally taken place and become the starting point 

 of new races, but he was none the less unshaken in the 

 conviction that this process was exceptional and extraor- 

 dinary, and that, as a rule, a new species originated 

 by the gradual building up of minute and even insig- 

 nificant deviations from the average characters of an old 

 species, which deviations we now call fluctuations. We 

 know with what tenacity he held this view to the end of 

 his life. For the doctrine of ''insensible gradations," 

 which touched mainly a minor premise in his general 

 argument for evolution, Mr. Darwin was, unhappily, 

 almost willing to relinquish the essence of the whole 

 matter, which was his claim to the discovery of a vera 

 causa in the evolutionary process. Notwithstanding 

 the prior claim of Patrick Matthew, and the partial antici- 

 pation of Alfred R. Wallace and others, the establishment 

 of the theory of natural selection was Mr. Darwin's most 

 original and greatest achievement. Time has proved that 

 he could have afforded to stand upon the general validity 

 and applicability of this theory though every step m his 

 argument in its favor had needed review and modifica- 

 tion; for each passing year but adds to the impregnable 

 mass of proofs by which it is affirmed and supported. 

 Properly regarded, the mutation theory does not antag- 

 onize nor weaken the doctrine of natural selection-on 

 the contrarv, it merelv offers itself as a helpful substitute 

 for, or adjunct to, one of Darwin's subordinate steps m 

 the approach to a consistent philosophy of the origin ot 

 species, leaving the last great cause of evolution as 

 efficient as ever. It is, therefore, one of the tragedies 01 

 science that in this matter Darwin should have been 

 ready to surrender his main position rather than to re- 

 ceive and to join forces with those who were coming to 

 his aid, but whom he failed to recognize as friends. 



