DE VRIES' "MUTATION" 89 



ated the existence of the solid crust of the 

 earth as at most hundred million years. 

 Joly, by calculating the amount of dissolved 

 salts, and Dubois by the amount of lime, es- 

 timated the age of the rivers, Joly giving as 

 probable fifty-five and Dubois thirty-six mil- 

 lions of years. 



"All in all,'' concludes DeVries, "it seems 

 evident that the duration of life does not com- 

 ply with the demands of the conception of 

 very slow and continuous evolution." Muta- 

 tion, with its sudden leaps, has no such dif- 

 ficulty, and, — "The demands of the biologists 

 and the results of the physicists are harmon- 

 ized on the ground of the theory of mutation." 



In order properly to estimate the sociolog- 

 ical significance of DeVries' theory it will be 

 necessary to go back more than a century, and 

 observe the sociological import of the leading 

 biological ideas of that period. 



And here let us remark, that nobody knows 

 better than we do the danger of transplanting, 

 without criticism, biological theories into the 

 field of sociology. Nevertheless, our oppo- 

 nents have never lost an opportunity to twist 

 and distort science, if perchance by any pos- 

 sibility it could be made to contradict any- 

 thing that had so much as the semblance of 

 Socialism. We, however, have always insisted 



