STUDIES ON THE DYNAMICS OF MORPHOGENESIS 303 



or other. This second zooid in Planaria is an excellent illus- 

 tration of the fact that a new organism developing from a part 

 of an old one may attain a certain clearly distinguishable degree 

 of physiological individuality before it becomes morphologically 

 recognizable. 



2. The question of 'wholeness' 



The whole in regulation is often sharply contrasted with a partial 

 result as if the two were separated by some hard and fast natural 

 distinction. It is of course true that in many cases there is not 

 the slightest difficulty in distinguishing between a whole and some- 

 thing that is not a whole. On the other hand there is not the 

 least reason to believe that all 'wholes' are alike or even that 

 they possess the same degree of ' wholeness' : in fact the data of 

 variation show us very clearly that they differ from each other in 

 a multitude of ways and that there is no clear distinction between 

 wholes and not wholes. The notion applied to organisms of 

 the whole as opposed to the not whole is like other human con- 

 ceptions in that it corresponds to no clearly defined and limited 

 group of objects in nature, but is merely a grouping made from 

 individual or collective experience for convenience of thought. 



In the above described experiments on Planaria we can 

 readily distinguish certain results of regulation as not wholes, 

 but between these and what for convenience we term normal 

 wholes there are all possible intermediate gradations. In the 

 process of head formation, for example, we see all stages of 

 completeness from what we have termed headless, on the one 

 hand, to normal heads on the other. But there cannot be the 

 least doubt that these normal heads also differ from each other 

 in greater or less degree and in various ways. 



Moreover, in examining the course of regulation we find that 

 different pieces attain wholeness in very different ways. The 

 pieces from different regions of the body illustrate this point. 

 Driesch has designated such regulations as "equifinal" but this 

 term is like the word ''wholeness" merely a convenient notion. 

 There is not the least reason for believing that pieces of Plan- 



