442 ANNALS NEW YORK ACADEMY OF SCIENCES 



mutationists now call "fluctuations," and, second, those radical and gener- 

 ally extensive de%-iations from type which constitute an actual break with 

 the species, variety or race, and which are substantially what we of these 

 later times have named "mutations." There are places in Darwin's works 

 where the two kinds of variation just mentioned are spoken of as "indefinite " 

 and "definite" and as results, respectively, of the indirect and the direct 

 action of the conditions of life, and once only, I think, he uses the term 

 "fluctuating variability" as synonymous with indefinite variability.^ Now 

 I do not assume to say that the realization of these distinctions by Mr. 

 Darwin proves that he clearly foresaw the present-day mutation theory 

 with its foundation in the principle of unit characters, but I think it is true 

 that he had at least a glimpse of the coming modifications to be required 

 in his own theory to meet the then dawning truth. De Vries declares that 

 his own field researches and testing of native plants are based "on the 

 hypothesis of unit- characters as deduced from Darwin's Pangenesis," which 

 conception, de Vries points out, "led to the expectation of two different 

 kinds of variability, one slow and one sudden." ^ 



But the main point I wish to dwell upon at present is that Darwin recog- 

 nized, at least dimly, a kind of variabihty the results of which were essen- 

 tially different from the "indi\ddual" or "indefinite" variations, which 

 mistakenly seemed to him alone capable of being acted upon by selection. 

 He was sorely puzzled by what he saw and realized in this direction, for he 

 had spent more than twenty years of intense thought in elaborating his 

 theory that new species were evolved from older ones by the gradual build- 

 ing up of new characters from extremely small differences, and he feared 

 that the admission of saltation in any form meant the undermining of the 

 foundations he had labored so hard to construct. He had once said: 



"When we remember such cases as the formation of the more complex galls, 

 and certain monstrosities, which cannot be accounted for by reversion, cohesion, &c., 

 and sudden strongly-marked deviations of structure, such as the appearance of a 

 moss-rose on a common rose, we must admit that the organization of the individual 

 is capable through its own laws of growth, under certain conditions, of undergoing 

 great modifications, independently of the gradual accumulation of slight inherited 

 modifications." ^ 



In the last edition of the "Origin of Species," however, which was pub- 

 lished in the year of the author's death, although he introduces this apology: 

 "In the earlier editions of this work I under-rated, as it now seems probable, 



1" Animals and Plants Under Domestication," 2d ed., Vol. II, pp. 280, 281, 345. 

 ' " Species and Varieties, their Origin by Mutation," 2d ed., 1906, p. 689. 

 » " Origin of Species," 5th ed., 1869, p. 151. 



