THE 



POPULAR SCIENCE 



MONTHLY. 



APRIL, 1903. 



ON THE ORIGIN OF SPECIES.* 



By Professor HUGO de VRIES, 



UNIVERSITY OF AMSTERDAM. 



WHAT are species? To answer this question is as difficult now 

 as it was in the days of Linnaeus. Formerly it was supposed 

 that a certain number of forms had been created, and that these, obey- 

 ing natural laws as yet undiscovered, had split up and so given rise 

 to groups, which afterwards were called genera. Such genera were 

 clover, rose and buttercup, plums, apples and pears. Among them, 

 by the addition of a name, certain species were distinguished, such as 

 red clover, white clover, etc. 



Linnaeus, in his first publications, adopted the above view. 

 'Each genus is created as such,' is one of his best known theses. 

 Later he changed this in so far as to declare species created, i. e., 

 those species which he recognized as such, and which he had 

 endowed with binomials. In this manner, the power to split up, to 

 produce new forms, and thus to form groups, was transferred to the 

 species, which offered the great advantage, that, since species greatly 

 surpassed the genera in number, the necessary number of splittings 

 was correspondingly reduced. 



Next to the disciples of Linnaeus and a few others who still ad- 

 hered to the "old doctrine, there soon arose a group of botanists and 

 zoologists who went much farther in applying the principle of Lin- 

 naeus than was intended by him. The former continued to consider 



* Translated from ' Album der Natur,' by H. T. A. Hus, Assistant in 

 Botany, University of Amsterdam, and revised by the author. Cf. 'Die Muta- 

 tionstheorie, Versuche und Beobachtungen iiber die Entstehung von Arten im 

 Pflanzenreich.' Bd. I., Entstehung der Arten durcb Mutation, Leipzig, Veit & 

 Co., 1901. 



VOL. IiXII. 31. 



