212 POPULAR SCIENCE MONTHLY. 



thereby intends to imply that they form more numerous single varia- 

 tions and have thus a better opportunity to split up again into further 

 species — so far de Vries (pp. 24-26). 



I have purposely insisted on these points, because here and there a 

 tendency seems to prevail to look upon Darwin's views on the origin of 

 species as unsatisfactory and obsolete, and to proclaim the necessity 

 of replacing them by a brand new hypothesis with which the name of 

 de Vries should be coupled. These tendencies are in great favor with 

 those that bear a grudge to the so-called Darwinism for other than 

 scientific reasons, and who in their innermost heart would at the same 

 time like to see a similar fate reserved for de Vries 's demonstrations, 

 and even for the whole theory of evolution. 



We have, however, seen in de Vries 's own words how little he con- 

 siders himself an antagonist of Darwin. On the contrary, his great 

 and imperishable merit consists in this, that his important and ex- 

 tensive experiments have provided us with a reliable basis concerning 

 a subject about which Darwin had not fully made up his mind. 



Darwin seems to have suspended his judgment; at all events, he 

 has not drawn a hard and fast line between the results which artificial 

 selection can attain when applied to fluctuating variations, on the one 

 hand, and to mutations, on the other. 



The experiments which de Vries has continued during many years 

 on the two divergent processes, which Darwin has not sufficiently kept 

 separate, have justified him in claiming that now, for the first time — 

 forty years after the appearance of the 'Origin of Species' — the actual 

 birth of a species has been observed by him. He has thus opened up a 

 most extensive field for further investigations by other naturalists, and 

 he has undoubtedly put an end to useless polemics which often threaten 

 to become yet further burdened by subtleties. 



Far from having undermined Darwin's Darwinism, de Vries has 

 completed, purified and simplified it. To Wallace's Darwinism, how- 

 ever, de Vries has dealt a severe blow, Wallace having attached no 

 significance to 'single variations' as possible sources of new species; 

 whereas Darwin has always continued to acknowledge their importance 

 as such, even though he did not thoroughly understand the laws to 

 which fluctuating variability is subject. Even Weismann, who has 

 only partially appreciated Darwin's philosophic indecision and who 

 has, without wavering, followed a road which has now landed him in 

 his 'germinal selection,' has undoubtedly taken notice of de Vries 's 

 experimental treatment of the subject with interest, though probably 

 not with personal satisfaction. 



Let us now try to picture to ourselves what conclusions de Vries 

 has been able to reach experimentally with respect to the phenomena 

 of mutation, and what he has taught us concerning the all-important 

 question: How have species originated? 



