EXPERIMENTAL MORPHOGENESIS 75 



but in which the whole of the morphogenetic action to be 

 performed is transferred in its single parts to the single 

 parts of the body which is accomplishing restoration : each 

 of its parts has to take an individual share in the process 

 of restoration, effecting what is properly called a certain 

 kind of " re-differentiation " (" Umdifferenzieruug "), and this 

 share varies according to the relative position of the part 

 in each case. Later on these statements will appear in 

 more correct form than at present, and then it will become 

 clear that we are fully entitled to emphasise at the end of 

 our criticism of Weisrnann's theory, that his hypothesis 

 relating to restorations can be no more true than his theory 

 of development proper was found to be. 



And now we shall pass on to our positive work. 



We shall try to sketch the outlines of what might 

 properly be called an analytical theory of morphogenesis ; 

 that is, to explain the sum of our knowledge about organic 

 form-production, gained by experiment and by logical 

 analysis, in the form of a real system, in which each part 

 will be, or at least will try to be, in its proper place and 

 in relation with every other part. Our analytical work 

 will give us ample opportunity of mentioning many im- 

 portant topics of so-called general physiology also, irrespective 

 of morphogenesis as such. But morphogenesis is always to 

 be the centre and starting-point of our analysis. As I 

 myself approach the subject as a zoologist, animal morpho- 

 genesis, as before, will be the principal subject of what is to 

 follow. 



