WILLIAM ROUX'S THEORY 173 



every detail of Roux's theory. This theory, as we said 

 before, is not a theory of heredity, for the struggle 

 between parts and functional stimulation can only 

 account for the appearance of general histological 

 and anatomical characters which may be, and in fact 

 are, common to all the individuals of one species, if 

 not of one family or genus. They do not account, 

 however, for any hereditary individual likeness. On 

 the other hand, the inheritance of acquired characters 

 is postulated by Roux as a logical necessity of his 

 theory, but he does not explain its workings. Fur- 

 thermore when Roux states that the competition 

 among cells f,or space and food results in a more defi- 

 nite specialisation, he does not give any reasons for 

 this phenomenon. What he says concerning the rela- 

 tive proportions of the various chemical substances in 

 one cell is perfectly clear, for it is natural that the 

 most favoured one should increase; but it is not cer- 

 tain that the same cause could produce a multiplica- 

 tion of the cells. 



Other objections could be presented. Plate re- 

 marks, for instance, that, while activity sometimes de- 

 velops an organ, it sometimes wears it out (as in the 

 case of teeth) and that there are cases of uncompen- 

 sated fatigue (in sensorial organs) or of spontaneous 

 hypertrophy, etc. 



In spite of all the defects of his theory and in spite 

 of all the questions it leaves unanswered, Roux de- 



