450 ANNALS NEW YORK ACADEMY OF SCIENCES 



from the main stem. I think he also substantially admitted that such new 

 species attained their full constancy at once. As to the fourth aflBrmation of 

 de Vries, with reference to elementary species and retrograde varieties, 

 Darwin had no knowledge, for the distinction is original with de Vries. 

 Darwin believed, as a general proposition, that "species are only strongly 

 marked and permanent varieties, and that each species first existed as a 

 variety," ^ but, of course, in admitted cases of mutation this can not be true; 

 and if Darwin had been obliged to concede de Vries's seventh proposition, 

 the fourth might w^ell have been allowed to go with it. The same is doubt- 

 less the case concerning de Vries's fifth law, which sets forth in effect that 

 similar mutants are thrown off by many individuals of the same species at 

 about the same time. As we have already seen, Mr. Darwin was convinced 

 that if, for example, he were to admit the origin by mutation of a species of 

 flying animal, for the reasons urged by Mr. Mivart, he would be compelled 

 to assume "that many individuals varied simultaneously." I, therefore, 

 do not see that he would have been interested, from a theoretical point of 

 view, in disputing either of the two last-named declarations of de Vries 

 except in connection with his seventh and last law, to which I shall presently 

 refer. The sixth law of de Vries, which aflarms that mutations take place 

 in nearly all directions, is practically the equivalent of Darwin's first law 

 that all organisms vary continually and in every part of their structure, 

 provided it is agreed that mutations are only quantitatively different from 

 Darwin's "individual variations," which was Darwin's o^ti view. In so 

 far as Darwin admitted the occurrence of mutation at all, he must have agreed 

 that it could proceed in any 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 compelled 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 un shaken in the conviction that this 

 process was exceptional and extraordinary, and that, as a rule, a new species 

 originated by the gradual building up of minute and even insignificant 

 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 anticipation by Alfred R. Wallace and others, the establish- 



» "Origin of Species," 6th ed., 1882, p. 412. 



