I20 THE HISTORY OF CEEATION. 



All the naturalists and philosophers with whom we have 

 become acquainted in this brief historical survey, as men 

 adopting the Theory of Development, merely arrived at the 

 conception that all the different species of animals and 

 plants wliich at any time have lived, and still live, upon 

 the earth, are the gradually changed and transformed de- 

 scendants of one or some few original and very simple 

 prototypes, which latter arose out of inorganic matter by 

 spontaneous generation. But none of them succeeded in 

 placing this fundamental element of the doctrine of descent 

 in relation with some cause, nor in satisfactorily explaining 

 the transformation of organic species by the true demonstra- 

 tion of its mechanical antecedents. Charles Darwin was 

 the first who solved this most difiicult problem, and this 

 forms the broad gulf which separates him from his pre- 

 decessors. 



The special merit of Charles Darwin is, in my opinion, 

 twofold: in the first place, the doctrine of descent, the 

 fundamental idea of which was already clearly expressed by 

 Goethe and Lamarck, has been developed by him much 

 more comprehensively, has been traced much more minutely 

 in all directions, and carried out much more strictly and 

 connectedly than by any of his predecessors ; and secondly, 

 he has established a new theory, which reveals to us the 

 natural causes of organic development, the acting causes 

 (causae efficientes) of organic form-production, and of the 

 changes and transformations of animal and vegetable species. 

 This is the theory which we call the Theory of Selection, or 

 more accurately, the Theory of Natural Selection (selectio 

 naturalis). 



When we reflect that (with the few exceptions above men- 



