198 The Origin of Species by Mutation. 



far as this circumstance allows us to judge, these new 

 species are as a rule just as constant as the older so-called 

 "good" species. 



§ 26. THE HYPOTHESIS OF INDISCRIMINATE 



MUTABILITY. 



The chief merit of Darwin's theory of selection was 

 that it explained the adaptation which is seen on all 

 hands in organic nature on purely natural principles and 

 without the aid of any teleological conception. It is be- 

 cause it does this so completely that the theory of descent 

 has gained such universal acceptance. The universal 

 belief in the kinship of living forms, in its turn now 

 makes the experimental study of the manner in which 

 one species arises from another, possible. Nay, it chal- 

 lenges us to such an inquiry. How the species which 

 exist at the present time arose in the past is evidently a 

 historical question which can only be directly answered 

 in a very few cases. But the determination of the mode 

 of origin of species must soon become the subject of 

 inquiry just like any other physiological process. 



According to the Darwinian principle, species-form- 

 ing variability^ — mutability — does not take place in defi- 

 nite directions. According to that theory, deviations take 

 place in almost every direction without preference for 

 any particular one, and especially without preference for 

 that direction along which differentiation happens to be 

 proceeding. Every hypothesis which differs from Dar- 

 win's in this respect must be rejected as teleological and 

 unscientific. 



The struggle for existence chooses from among the 

 mutations at its disposal those which are the best adapted 



^ Intracellular e Pangenesis, pp. yZy 210, etc. 



