G4() MUTATION THEORY <)F PROFESSOR DE VRIES. 



the assumed extreme antiquity of the habitable condition of the earth 

 has been drawn from the theory of the origination of organic forms 

 by the slow process of natural selection. Indeed such extreme antiq 

 uity has been assunKnl expressly to meet the demands of that theorj-. 

 A general acceptance of the mutation theory will remove that question 

 from such discussions, and geological science would probably not suffer 

 by the loss. 



The great master, Darwin, in one of his aphorismic utterances, stiys 

 that in "scientific investigations it is permitted to invent any hypoth- 

 esis, and if it explains various large and independent classes of facts 

 it rises to the rank of a well-grounded theory." One can not doubt 

 that if he were now living he would be among the first to give the 

 mutation theorv respectful consideration. 



Whatever the final verdict of biologists may be concerning the theory 

 that Professor de Vries has so elaborateh' proposed, the subject is so 

 important and the presentation is so carefully made that no student of 

 any branch of biology can afford to ignore it. 



