128 THE THEORIES OF EVOLUTION 



characters are produced which strike an average be- 

 tween the characters of both parents. 



In the fecundated ovum, the nature of the micella?, 

 their grouping, the periods of tension and relaxation, 

 of activity and inactivity, which produce the various 

 characters at a certain time and in a certain place, 

 are all predetermined and can hardly ever be influ- 

 enced by external conditions. External conditions, 

 however, may modify the tension of the strands, which 

 may be, for instance, strengthened by use, and there- 

 fore become more sensitive, or on the other hand 

 weakened by disuse and reduced to a passive condi- 

 tion. Those modifications spreading through the tis- 

 sues eventually reach the germ cells and are trans- 

 mitted to the next generation. 



Such is Naegeli's explanation of the transmission 

 of characters; it is very indefinite and open to much 

 criticism. He believes that characters are adaptive, 

 but takes this view for purely finalist reasons. The 

 necessary modifications are produced in the organism, 

 he thinks, to fill certain wants created by certain in- 

 fluences exerting themselves on the organism. Ex- 

 planations of this kind explain nothing. 



Naegeli's entire conception of the evolution of be- 

 ings is pervaded with the same spirit. The idioplasm 

 of living things has possessed since the very beginning 

 of life certain internal evolutive tendencies which 

 have determined the ulterior phylogenetic develop- 



