ENVIRONMENT AND EVOLUTION KROPOTKIN. 421 



(heavy manuring, keeping the seedlings wide apart, and so on) was 

 the first condition for obtaining such inheritable variations. 1 But 

 later on, accepting the teachings of Weismann, he separated the 

 " nutrition variations," which, he maintained, were not inheritable, 

 from the " mutations." The latter were inherited, because they were 

 originated by " congenital " variations, suddenly appearing for some 

 causes unknown in the germ plasm, at certain periods of the life of 

 the species. Each species, he said, has such a period, during which 

 it can give origin to new species. 



However, it was soon recognized by most botanists that the value 

 of the Oenothera sports for a theory of descent had been overesti- 

 mated. From accurate researches made in the United States, at 

 Harlem, and in the environs of Liverpool, it appeared that the 

 species described as Oenothera lamarchiana had a long history: it 

 was cultivated in Europe as early as the middle of the eighteenth 

 century, and it easily could be a crossing of two other species of the 

 evening primrose. Hence its great variability. 2 Moreover — and 

 this is an essential point, already noticed by Darwin — a variation is 

 often described as a " sudden " one simply because the minute 

 changes which were leading to its appearance were not taken notice 

 of. In reality, leaving aside those unimportant individual differ- 

 ences which but feebly affect some organs, Darwin found no sub- 

 stantial difference between the sports and the inheritable fluctuating 

 variations due to environment. 3 As to the idea that sports might 

 explain the appearance of new species, Darwin very wisely pointed 

 out that purely accidental sports could not have played such a part 

 in the evolution of new species, because they would not offer that 

 accommodation to environment which can only be supplied by a 

 definite and cumulative variation under the influence of a new envi- 

 ronment- — this variation being aided by natural selection. 



At any rate, those who have seriously studied the whole subject 

 of evolution and heredity, like Yves Delage, Johannsen, Plate, 

 and many others, do not now attribute to "mutations" the 

 importance that was going to be attributed to them a few years 



1 Cf. Die Mutationstheorie, vol. i, Leipzig, 1901, pp. 93, 97-100, and in fact all the 

 fourth chapter. Also his earlier articles, L'unite dans la variation and Alimentation et 

 selection, summed up in Mutationstheorie. 



- Many important data concerning variation in Oenotheras will be found in the mono- 

 graph of Messrs. D. T. MacDougal, A. M. Vail, and G. II. Shull, Mutation, Variation and 

 Relationships of Oenotheras, Washington (Carnegie publications), 1907. 



3 " Monstrosities graduate so insensibly into mere variations that it is impossible to 

 separate them" (Variation, ii, 297-298). He considered that "variability of every kind 

 is directly or indirectly caused by changed conditions of life " (p. 300) ; and " of all 

 causes which induce variability, excess of food, whether or Dot changed in nature, is 

 probably the most powerful" (p. 302). 



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