TRANSMISSION OF ACQUIRED CHARACTERS. 413 



characters in the body which have arisen from changes in the 

 germ. In this way we might perhaps prevent the possibility of 

 misunderstanding. We maintain that the ' somatogenic ' characters 

 cannot be transmitted, or rather, that those who assert that they 

 can be transmitted, must furnish the requisite proofs. The somato- 

 genic characters not only include the effects of mutilation, but 

 the changes which follow from increased or diminished performance 

 of function, and those which are directly due to nutrition and any 

 of the other external influences which act upon the body. Among 

 the blastogenic characters, we include not only all the changes 

 produced by natural selection operating upon variations in the 

 germ, but all other characters which result from this latter 

 cause. 



If we now wish to place Hoffmann's results in their right 

 position, we must regard all of them as ' Mastogenic ' characters, 

 for no one of them can be considered as belonging to the group 

 which has been hitherto spoken of as ' acquired,' in the literature 

 of evolution : they are not due to somatogenic but to llastogenic 

 changes. The body of the plant the soma has not been directly 

 affected by external influences, in Hoffman's experiments, but 

 changes have been wrought in the germ-plasm of the germ-cells 

 and, only after this, in the soma of succeeding generations. 



There is no difficulty in finding facts in support of this state- 

 ment, among Hoffmann's experiments. The proof chiefly lies in 

 the fact that in no one of his numerous experiments did any 

 change appear in the first generation. The seeds of different 

 species of wild plants, with normal flowers, were cultivated in 

 the garden and in pots (thickly sown in the latter case), but no 

 one of the plants produced by these wild seeds possessed a single 

 double flower. It was only after a greater or less number of 

 generations had elapsed that a variable proportion of double 

 flowers appeared, sometimes accompanied by changes in the leaves 

 and in the colours of the flowers. This fact admits of only 

 one interpretation; the changed conditions 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 



