THEORY OF ORGANIC EVOLUTION. 



13. ONTOGENETIC DEVELOPMENT OF THE DETERMI- 



NANTS. 



Since the capability of the primordial plasma to 

 grow is the original and only vital quality (Anlagi), 

 the whole ontogeny in this first stage consists in the 

 growth of the detached parts to the adult size. In 

 the same way the development of the determinants 

 in all the following stages is nothing more than the 

 growth of the substance detached as a germ cell 

 after the manner of the changes in the character of 

 the idioplasm in the course of phylogeny. In this 

 manner all determinants may in the lower stages of 

 organization reach development, but in the higher 

 stages an increasing number of them must remain 

 latent. 



Among the viable determinants there are some 

 that develop unconditionally during each ontogenetic 

 period; there are also alternative determinants of 

 which one or the other unconditionally develops; 

 lastly, there are some that develop only under favor- 

 able circumstances. Which of two alternative 

 determinants shall develop depends sometimes on 

 internal, sometimes on external causes, according 

 as the specific determinant has arisen phylogenetic- 

 ally through the action of internal or external causes. 

 Climatic and nutritive influences especially affect 

 the appearance of indefinitely developing deter- 

 minants. Just so, when a determinant may develop 



