On the Mechanical Conception of Nature. 693 



cycles of variation in heterogeneous species). 

 These views are finally completely justified by 

 their furnishing the only possible theoretical 

 formulation of variability on which a mechanical 

 conception of organic development can be based. 

 That such a conception is not only admissible, 

 but is unavoidable, at least to the naturalist, I 

 have already attempted to prove. 



