HOW SPECIES HAVE ARISEN 499 



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. 



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 

 varieties. There seems to be no good reason for doubting that 

 both variation and mutation have been and are efficient in the 

 production of new species. 



