174. THE THEORIES OF EVOLUTION 



serves much credit for having drawn the attention of 

 scientists to a factor as powerful as functional stim- 

 ulation and for having proved that it accounts for 

 many facts of prime importance. In this respect, 

 lioux's theory differs widely from Weismann's. The 

 latter leaves nothing unexplained or unprovided for; 

 its details are above criticism but its basis is erroneous. 

 Roux neglects the details, leaves many problems un- 

 solved, but the main thesis is correct and likely to lead 

 investigators along the right path. 



The idea of functional stimulation is not new; it 

 is derived from the Lamarckian principle of the crea- 

 tion of the organ by the function. By showing the 

 practical application of that principle and by extend- 

 ing it even to passive organs and to the phenomena of 

 cell life, Roux has gone a long step forward. The 

 theory of functional stimulation with its corollary, the 

 inheritance of modifications due to this factor, seems 

 to us inspired by the Lamarckian point of view, in 

 spite of the idea, however correct it may be, of the 

 competition between parts of the organism which 

 gives it a slight selectionist tinge. 



The shortcomings of the theory of the struggle be- 

 tween determinants, in Weismann's system of ger- 

 minal selection, make it evident that the theory of the 

 struggle between parts cannot strengthen the position 

 of the selectionists. On the other hand, a typical 



