414 



change became great enough to produce a visible character in the 

 aoma developed from it, such as, for example, the appearance of 

 a double flower. Now the idioplasm of the first ontogenetic 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 sufficient to produce changes in the soma, which appeared 

 as visible characters in either the flower or leaf l . 



In addition to the above-mentioned cases Hoffmann also quotes 

 some facts of a somewhat different kind. He succeeded in in- 

 ducing 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 experi- 

 ments 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 years. Darwin some time 

 ago pointed out in his work upon ' The Variation of Animals and 

 Plants under Domestication,' that, in the case of the pansy and 

 all other ' improved ' garden flowers, the wild form remained un- 

 changed for many generations after its transference to the garden, 

 apparently uninfluenced by the new conditions of life. At length 

 single varieties began to appear, and these were further developed 

 by artificial selection and appropriate crossing, into well-marked 

 races distinguished by peculiar colours, forms, etc. 



In these cases also, changes in the germ-plasm are the first 



1 Compare on this point Nageli in his ' Theorie der Abstainmungslelire. 1 This 

 writer also concludes from similar facts that external influences have wrought in 

 the idioplasm, changes which were at first 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 

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

 germ-plaMn and soinatoplasni. 



