OTHER FACTORS OF EVOLUTION 133 



to correlated changes in the soma, rather than induced in the germ- 

 plasm simultaneously as a result of the operation of the same causes 

 which pi-oduce the definite changes in the soma, is a question 

 perhaps of some theoretical interest (though practically insoluble) : 

 but it is not the question with which we are immediately con- 

 cerned ' and is of little or no importance since Weismann himself 

 now admits the diplogenetic process. 



Irrespective then of the mode in which it is brought about, we 

 see that Weismann frankly admits the whole point in dispute — 

 namely, that acquired characters can be, and are, frequently in- 

 herited. Thus speaking of another experiment of Hoffmann's he 

 says : — " He succeeded in inducing considerable changes in the 

 structure of the root of the wild carrot (Daucus carrota) by means 

 of the changes in nutrition implied by garden cultivation. These 

 changes also proved to be hereditary." References to many other 

 striking changes of this kind will be found in an article on ' Recent 

 Science ' by Prince Kropotkin. " Thus, he says, Vilmorin ob- 

 tained the cultivated carrot out of the wild one in five generations. 

 Carriere did the same with the radish, and Buckman the same with 

 parsley. Multitudes of experiments have been recorded showing 

 that a direct action of external conditions will even produce 

 'adaptive' changes in plants, so that, as the above-mentioned 

 writer says, "when we see that environment so rapidly itself 

 creates the adaptation, we shall necessarily be more cautious in 

 speaking of the natural selection of quite accidental individual 

 variations." 



It seems only natural to suppose that changes wrought by 

 external conditions should require four or five generations to attain 

 their maximum, whether such changes take effect chiefly upon the 

 soma or upon the germ-plasm ; and what more natural than to 

 suppose when a plant has been thus altered under a given set of 



" In one of the earlier pages (p. 403) of this same " Essay," he had said : — 

 " But obviously it is of no importance for the question of the transmission of 

 acquired characters, whether the changes directly produced by external in- 

 fluences upon the soma of an individual are greater or smaller : the only question 

 is whether they can be transmitted. If they can be transmitted, the smallest 

 changes might be increased by summation in the course of generations, into 

 characters of the highest degree of importance. It is in this way that Lamarck 

 and Darwin have supposed that an organism is transformed by external in- 

 fluences." But from the point of view of " the only question " in dispute, it is 

 quite immaterial whether the changes begin in the soma, or in the germ-plasm, 

 or in both concurrently. 



^ " Nineteenth Century and After," 1901, Vol. 50, pp. 424-438. 



