43 THEORY OF ORGANIC EVOLUTION. 



influences in each ontogeny and are not inherited; 

 they represent nutrition varieties, are experimentally 

 demonstrable, and constitute the subject matter of 

 experimental physiology. (2) The others are 

 inherited and again transmitted ; they belong to the 

 physiology of the idioplasm. This subject is mainly 

 occupied with the origin of the determinants, hence 

 with the formation of varieties and species. It is 

 not the subject of experiment, and constitutes the 

 phylogeny or the physiology of the formation of 

 determinants. A sub-division of this subject is 

 occupied with the development of the determinants 

 already present, hence with the formation of races. 

 It is elucidated especially by experiments in cross- 

 ing and may be designated as the physiology of the 

 development of the determinants. 



The morphological phenomena which find their 

 application in taxonomy, belong exclusively to 

 phylogeny. Their ontogenetic history does not 

 explain their true significance; this can be known 

 only in a phylogenetic way by comparison of one 

 phenomenon with those phenomena from which it 

 has arisen in the course of evolution. 



33. PLANT CLASSIFICATION FROM THE STANDPOINT OF 



PHYLOGENY. 



Spontaneous generation has taken place at all 

 times and in all places, in as far as the necessary 

 conditions were concurrently present. (See page 47). 



