Conclusion. 213 



either ( 1 ) the survival of the most favorable individuals 

 within the hmits of the constant species or in the forma- 

 tion of local races or (2) ''the survival of the fittest spe- 

 cies" as the basis for the theory of descent. The two 

 expressions are quite independent of one another and 

 refer to two entirely different spheres of inquiry. 



6. According to the theory of mutation species have 

 not arisen gradually as the result of selection operating 

 for hundreds, or thousands, of years but discontinuously 

 by sudden, however small, changes. '' In contradistinction 

 to fluctuating variations which are merely of a plus or 

 minus character the changes which we call mutations are 

 given off in almost every manner of new direction. They 

 only appear from time to time, their periodicity being 

 probably due to perfectly definite but hitherto undis- 

 covered causes. 



The theory of the inheritance of acquired characters 

 comes under the heading of fluctuations. Acquired char- 

 acters have nothing to do with the origin of species. Nor 

 can the theory of descent be applied to the solution of 

 social problems. 



