164 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



may be differentiated back and be replaced by a new 

 pharynx, which is smaller. 



It is not death and sloughing of parts that occurs in 

 these cases, 1 but a real process of active morphogenesis ; not, 

 however, a process consisting in the production of visible 

 manifoldness, but the opposite. Loeb was the first to lay 

 much stress upon this topic, and indeed, there may appear a 

 very strange problem in its wake : the problem, whether 

 all morphogenesis might be capable perhaps of going 

 backwards under certain conditions. 



It is important to note that in most 2 cases retro- 

 differentiation occurs in the service of restitution : it goes 

 on wherever restitution requires it. This fact alone would 

 show that not very much could be explained here by the 

 discovery of modern chemistry, important as it is, that one 

 and the same " ferment " or " enzyme " may affect both the 

 composition and the decomposition of the same compound, 

 We could regard what is called " catalysis " solely as an 

 agent in the service of entelechy. But this point also will 

 become clearer in another part of the work. 



1 Of course such a real decay of parts may happen in other cases. 

 a Certain cases of retro-differentiation occurring under conditions of strict 

 fasting will be described in a later chapter. 



