Mutations 



59 



the slow changes advocated by Lamark. His ideas were 

 theoretical, however, and at that time were not borne out 

 by experimental evidence. 



Darwin recognized the appearance of sudden variations 

 of a marked character, such as is seen in the origin of 

 large-crested Polish fowls and short-legged Ancon sheep. 

 He thought that these new and strange forms would be 

 lost soon by intercrossing and, being rare, that they pos- 

 sessed no value. He held that the slow accumulation 

 of minute fluctuating variations was the important factor 

 in evolution. 



De Vries' experiment with cenotheras. De Vries became 

 convinced long ago that Darwin's theory of the origin 

 of species through ac- 

 cumulation of minute 

 changes was not the only 

 means of creating new 

 types. He determined 

 to produce mutations ex- 

 perimentally, if possible. 

 His results in the forma- 

 tion of a new variety of 

 the corn marigold will be 

 described later. After 

 making preliminary ex- 

 periments with some 

 hundred species, de Vries 



finally decided upon (Enothera Lamarkiana as the most 

 suitable form to use (Figs. 17 and 18). "Only one of my 

 tests met with expectations. This species proved to be 

 in a state of mutation, producing new elementary forms 



FIG. 16. Hugo de Vries. 



