G3() MUTATION THEORY OF PROFESSOR DE VRIES. 



two species referred to originated from them then and there by spon- 

 taneous mutation. The latter inference accords with the author's 

 proposition, that in their wild condition mutating plants produce many 

 new species; that most of these perish in the strug'g-le for existence, and 

 that artificial cultivation protects all the new forms from destruction, 

 but is not of itself the cause of the origination of any. 



It seems to have been this exhibition of mutative vigor in the Even 

 ing Primroses that led its disting-uished observer to adopt those plants 

 as the chief subjects of his experimental studies, and it is for this 

 reason that so large a part of his book is devoted to the exhaustive 

 exploitation of plants belonging to the genus (Enothera. The results 

 plainly show the wisdom of that choice, for by careful protection and the 

 aid of artificial pollination he succeeded in obtaining from them a con- 

 siderable number of new species, which are as well defined in all their 

 attributes as are any of the other species of that genus. Moreover, he 

 continued from year to year his experiments with the new species thus 

 produced, as well as with the orig-inal forms, and he asserts without 

 hesitation that in all their attributes the new forms are not only 

 sharply defined but that those attributes are entirely constant from 

 and after the moment of their origin; and, furthermore, that all those 

 attributes are as heritable as are those of any of the other species. 

 He practiced both inter and intra specific artificial pollination, but, 

 although he obtained the reproduction of some of the new forms under 

 the former method, the origination of species de novo under his experi- 

 ments seems to have been wholly by aid of the latter method; that is, 

 his experiments seem to prove that cross fertilization is not only not 

 necessary to mutation, but that mutation is not materially accelerated 

 by it. It is well known that some authors claim that thousands of 

 species of living plants have originated by hybridization. The 

 second volume will treat fully of that subject and of its relation to true 

 mutation. 



The author supports all his statements with the most miimte account 

 of his experiments, the results of which he also discusses fully. These 

 facts and discussions are of such a character that it seems difiicult to 

 see how one can avoid accepting his conclusions without denying his 

 facts. Indeed, it may be frankly stated that should one accept his 

 conclusions the author will be thereby recognized as not only the pro- 

 pounder of a new and important biological theory, but the discoverer 

 of new and vital facts and principles relating to the origination and 

 perpetuation of organic forms. Furthermore, by accepting that theor}?^ 

 and admitting the facts upon which it is based, one must necessarily 

 regard the question of the origin of species as thereb}^ removed from 

 the purely theoretical to the concrete; that is, from an undemonstrable 

 hypothesis to a series of concrete propositions and practical demon- 

 strations. These are strong statements, but they indicate what one 



