STUDIES ON THE DYNAMICS OF MORPHOGENESIS 317 



piece and the sexual reproductive element except that the latter 

 is so highly specified physiologically that it requires special 

 stimulation to initiate the new series of processes while in the 

 pieces of the planarian isolation alone is sufficient. While I should 

 not for a moment maintain that the investigation of inheritance 

 in experimental reproduction can take the place, or obviate the 

 necessity of other methods of attack upon the problem of heredity, 

 yet I do believe that in such forms of reproduction we have the 

 problem given in somewhat simpler terms than in sexual repro- 

 duction and furthermore the possibility of controlling the size 

 of the reproductive element, the region from which it shall arise 

 and the conditions of its development, as well as the metabolic 

 conditions in the parent, afford various possibilities of experi- 

 mental analysis which are not given in sexual reproduction in 

 the higher animals. Believing that wherever reproduction 

 occurs in the organic world, there inheritance occurs also, I have 

 for years past regarded the field of 'form regulation' as of great 

 importance for the problem of heredity, though this feature has 

 not been emphasized in my published work thus far. But having 

 now acquired as I believe, a fairly satisfactory basis for future 

 investigation, I have felt it desirable to present my experimental 

 data with some regard to their bearing upon the problem of 

 heredity. The present paper is intended primarily to serve as a 

 foundation for what is to follow. 



