Summary and General Conclusions 459 



appears, and is inherited in its new form. From the re- 

 sults of De Vries it appears that mutations are sometimes 

 scattering, at' least in the case of the evening primrose. 

 From such scattering mutations, the smaller species or 

 varieties (in so far as these do not depend on local con- 

 ditions) arise. There is here an important point of agree- 

 ment with Darwin's idea in regard to evolution, inasmuch as 

 he supposed that varieties are incipient species. Our point 

 of view is different, however, in that we do not suppose these 

 varieties (mutations) to have been gradually formed out of 

 fluctuating variations by a process of selection, but to have 

 arisen at once by a single mutation. It also appears that in 

 some cases a single new mutation may develop in a species. 

 We may suppose that the new form might in such a case 

 supplant the parent species by absorbing it, or both may go 

 on living side by side, as will be more likely the case if they 

 are adapted to somewhat different conditions. 



A number of writers have supposed that evolution marches 

 steadily forward toward its final goal, which may even 

 lead in some cases to the final but inevitable destruction 

 of the species. By certain writers this view has been called 

 orthogenesis, although at other times the idea is not so much 

 that there is advance in a straight line, as advance in all 

 directions. This appears to be Nageli's view. It gives a 

 splendid picture of the organic world, as irresistibly marching 

 toward its goal, — a relentless process in some cases, leading 

 to final annihilation, a beneficent process in other cases, 

 leading to the fullest perfection of form of which the type is 

 capable. Compared with the vacillating progress which is 

 supposed to be the outcome of individual selection, this view 

 of progression has a grandeur that appeals directly to the imag- 

 ination. We must be guided, however, by evidence, rather 

 than by sentiment. The case will, moreover, bear closer 

 scrutiny. If evolution has indeed taken place by the survi- 

 val of a series of mutations, whose origin has no connection 



