33 THEORY OF ORGANIC EVOLUTION. 



12. CONDITIONS OF PHYLOGENETIC DEVELOPMENT OF 

 THE DETERMINANTS. ATAVISM. 



In the primordial condition, formation and devel- 

 opment of the determinants coincide, since the 

 plasma constituting the organism possesses the capa- 

 bility of growing by intussusception of new micella 

 and of changing this growth through the action of 

 inner and outer causes. But as the primordial 

 plasma differentiates into idioplasm and soma- plasm, 

 the formation of determinants consists in the transfor- 

 mation of the idioplasm, while the development of 

 determinants consists in the production of soma- 

 plasm and of non-plasmic substances under the influ- 

 ence of the idioplasm. 



Only the mature determinant is able to develop, 

 especially if, at the same time, a related and here- 

 tofore active determinant must be forced back into 

 the latent condition. But the determinant of an 

 absolutely new form of adaptation, which does not 

 take the place of a preceding one, must develop 

 enough before it can become outwardly manifest, 

 for it to be possessed of a sufficient amount of mol- 

 ecular energy to render its activity possible. For 

 this reason the characteristics of the developed organ- 

 ism change abruptly, notwithstanding the fact that 

 the transformation of the idioplasm has proceeded 

 very gradually. 



The configuration of the idioplasm becomes con- 



