STUDIES ON THE DYNAMICS OF MORPHOGENESIS 315 



tion with other experimental data. As regards the development 

 of a posterior end the case is somewhat different for in this species 

 correlative factors always play an important part in its forma- 

 tion. 



The experiments show beyond a doubt that there are two 

 factors which varv or exhibit a gradation along the axis, viz., 

 constitution, or what is essentially the same thing, metaboUsm 

 and its structural colloid field, and physiologic correlation. And 

 there is no evidence to indicate that the phenomena of polarity 

 depend on anything but these two factors. 



6. Heredity in the regulation of pieces 



Extended discussion of this aspect of my experiments must be 

 postponed until further data ire presented. Here attention may 

 be called to a few points, some of which are already famihar, 

 while others are less generally recognized. 



That the pieces inherit their capacity to form wholes, or, for 

 that matter, to form anything, is, I think, sufficiently evident. 

 The experiments show, however, that there are limiting factors 

 in such inheritance which are associated with the size of the 

 reproductive element and with its position in the body. In the 

 preceding sections the attempt has been made to analyze these 

 factors of size and region into terms of organization, with the 

 conclusion that any piece must possess a certain minimal organi- 

 zation along the axis in order to be capable of producing a whole. 

 In the cases which we have considered this organization is directly 

 inherited as a fraction of the organization of the whole animal. 

 In a later paper we shall consider the question as to whether it 

 may under certain conditions arise in other ways. This axial 

 organization is not directly related to the visible morphological 

 structure and is not necessarily anything very complex: as sug- 

 gested above it is probably a dynamic gradient or gradients with 

 the accompanying correlative factors. In short it may be of 

 essentially the same character as the polarity of the egg. 



The conditions which determine the formation of normal and 

 teratopthalmic wholes, as described above are of considerable 



