Theoretically Conceivable Kinds of Epigenesis 107 



sequence of the reciprocal action of the different parts 

 of the organism upon one another. 



We will call the first of these processes epigenesis 

 with preformistic germs, the other, epigenesis without 

 preformistic germs, or epigenesis proper. 



Further, each of these two processes can, theoretically, 

 be divided again into the two following categories. 



One can conceive of the reciprocal action of the dif- 

 ferent parts of the organism upon one another, as such 

 that no part whatever should ever be considered different 

 in any way, in so far as its formative action on the other 

 parts is concerned, from these other parts, but rather all 

 are to be regarded as equally necessary and of equal 

 value in this respect. Or, on the other hand one can 

 suppose that among all the parts there is one whose action 

 upon the other parts differs through some peculiarity 

 from the corresponding action of all other parts, so that 

 it acquires in comparison with the latter much greater 

 importance. 



We shall designate the first process with the name 

 "simple epigenesis," or briefly "epigenesis/' which would 

 be equally possible either with or without preformistic 

 germs, and we shall call the second in which the form- 

 ative action would on the contrary become specially local- 

 ized in a definite zone of the organism, by the name of 

 "localized or centralized epigenesis," or briefly "centro- 

 epigenesis." Practically it would be conceivable only 

 without preformistic germs. 



Finally, in all the different theories without pre- 

 formistic germs, one could conceive of the germinal sub- 

 stance as formed of a single homogeneous substance (or 

 a homogeneous mixture of different chemical substances), 

 or of a material which though not consisting of pre- 



