Centroepigenesis vs. Pre formation and Epigenesis 17 



germinal substance, and one suspects at once that it may 

 be just this substance which constitutes the central zone. 



If so it would follow that the central zone must be at 

 the same time the germinative zone, that is to say, the 

 place whence the sexual cells get the germinal substance 

 which makes them capable of reproduction. Let us 

 hasten to add now that the central zone must coincide 

 with the effective germinal zone, but may possibly be quite 

 separate and distinct from the apparent germinal zone. 

 The latter would be then only the place of formation of 

 the sexual cells, inasmuch as these constitute in a certain 

 sense the mere envelope in which later the germinal sub- 

 stance is assembled, which alone is able to give them 

 reproductive capacity. 



The hypothesis of centroepigenesis includes then that 

 of a continuous action exercised by the germinal sub- 

 stance upon the soma throughout the whole duration of 

 its development. We shall endeavor in the second chapter 

 to learn what is the nature of this action and we shall 

 reserve for consideration in the third chapter the central 

 zone itself, as well as other facts and arguments which 

 make its existence seem probable and which serve to make 

 the hypothesis clearer. 



We shall limit ourselves here to putting in special light 

 the fundamental characteristics which differentiate this 

 hypothesis as well from the preformistic as from the 

 epigenetic theories. 



/ While Weismann and the preformists in general con- 

 sider that the germ plasm separates itself before the com- 

 mencement of development from the portion set apart to 

 form the new organism, and remains passively aside in a 

 detached part of the soma until it later steps in to form 

 the future sexual cells; consequently it would not control 



