HOW SPECIES HAVE ARISEN 499 



t. 



The theory that species spring suddenly from mutations was 

 advanced by Professor Hugo de Vries, of Amsterdam, Holland, 

 in a work on the mutation theory, published in 1901 and 1903. 1 



Botanists at present are considerably divided on the question 

 of the origin of species, some believing that they are mainly 

 derived from the perpetuation and intensification of slight varia- 

 tions, while mutations are so infrequent as not to signify much 

 in this connection ; others, again, believe that mutations are the 

 source of species, and that variations can only give rise to varie- 

 ties. There seems to be no good reason for doubting that both 

 variation and mutation have been and are efficient in the pro- 

 duction of new species. 



1 For an English translation of the German original of this work see De 

 Vries-Farmer-Darbishire, The Mutation Theory, Chicago, 1910. 



