EXPERIMENTAL MORPHOGENESIS 11 



Q 



say that, especially in regeneration proper, the specific type 

 of the regenerative formation of any part may differ very 

 much from the ontogenetic type of its origin : the end of 

 both is the same, but the way can be even fundamentally 

 different in every respect. 



The Stimuli of Restitutions * 



But now we turn to the important question : what is 

 the precise stimulus 2 that calls forth processes of restitution ; 

 or, in other words, what must have happened in order 

 that restitution may occur? 



That the operation in itself, by its removing of mechanical 

 obstacles, cannot be the true stimulus of any restitutions, 

 is simply shown by all those restitutions that do not 

 happen at the place of the wound. If we took a narrower 

 point of view, and if we only considered regeneration proper 

 from the wound itself, we might probably at first be 

 inclined to advocate the doctrine that the removing of 

 some obstacles might in fact be the stimulus to the process 

 of restoration ; but, even then, why is it that just what is 

 wanted grows out? Why is there not only growth, but 

 specific growth, growth followed by specification ? The 

 removing of an obstacle could hardly account for that. 

 But, of course, taking account of all the adventitious 



1 For a fuller analysis compare my opening address delivered before the 

 section of "Experimental Zoology" at the Seventh Zoological Congress, 

 Boston, 1907: "The Stimuli of Restitutions" (see Proceedings of that 

 Congress). 



2 The problem of the stimulus of a secondary restitution as a whole must 

 not be confused with the very different question, what the single " formative 

 stimuli" concerned in the performance of a certain restitutive act may be. 

 With regard to restitution as a whole these single, "formative stimuli" 

 might properly be said to belong to its "internal means " in the widest 

 sense of the word. 



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