VII.] TRANSMISSION OF ACQUIRED CHARACTERS. 427 



changes in the leaves and in the colours of the flowers. This 

 fact admits of only one interpretation; the ciiangcd con- 

 ditions at first produced slight and ineffectual changes in the 

 idioplasm of the individual, which was transmitted to the 

 following generation : in this again the same causes operated 

 and increased the changes in the idioplasm which was again 

 handed down. Thus the idioplasm was changed more and 

 more, in the course of generations, until at last the change 

 became great enough to produce a visible character in the 

 soma developed from it, such as, for example, the appearance 

 of a double flower. Now the idioplasm of the first ont<jgcnetic 

 stage (viz. germ-plasm) alone passes from one generation to 

 another, and hence it is clear that the germ-plasm itself 

 must have been gradually changed by the conditions of life 

 until the alteration became sufiicient to produce changes in 

 the soma, which appeared as visible characters in either the 

 flow^er or leaf ^ 



In addition to the above-mentioned cases Hoffmann also 

 quotes some facts of a somewhat different kind. He succeeded 

 in inducing considerable changes in the structure of the root of 

 the wild carrot {Daucus carota) by means of the changes in 

 nutrition implied by garden cultivation. These changes also 

 proved to be hereditary. 



Unfortunately, I have not the literature of the subject at 

 hand, and hence I am unable to read the accounts of these 

 older experiments in extenso ; but it is sufficiently obvious that 

 in this case we are also concerned with a change which did 

 not become visible until after some generations had elapsed, 

 and which was therefore a change in the germ-plasm. 



Many instances of a precisely similar kind have been long 

 known, and one of them is to be found in the history of the 

 garden pansy, which Hoffmann has succeeded in producing 

 from the wild form, Viola tricolor, in the course of eighteen 



^ Compare on this point Nageli in his'Theoric dcr Abstammunps- 

 lehre.' This writer also concludes from similar facts that external 

 influences have wrought in the idioplasm, changes which were at fii-st 

 ineffectual, and which only increased during the course of generations 

 up to a point at which they could produce visible changes in the plant. 

 He does not, however, draw the further conclusion that these cbanges 

 only influence the germ-plasm, for he was not aware of the distinction 

 between germ-plasm and somatoplasm. 



