MUTATIONS 



127 



the sixth generation. The entire results of the eight generations 

 of breeding are given in the following table. 



EIGHT GENERATIONS OF A MUTATING STRAIN OF EVENING PRIMROSE 

 (0. Lamarckiana) 



In the opinion of the experimenter here are numbers enough 

 and types sufficiently, distinct to warrant the enumeration of 

 certain laws or principles that appear to govern the appearance 

 of mutants, especially in the species under observation. This 

 De Vries attempts to do, but without presuming to say how 

 closely they may apply to other strains of plants or animals. 



Laws of mutability for evening primroses. De Vries' experi- 

 ments. On the basis of his experiments with the evening prim- 

 rose the investigator announces the following laws of mutability 

 as applying to that species i 1 



1. "That new elementary species appear suddenly, without 

 intermediate steps." As proof he points out that no interme- 

 diate forms appeared to fill the gaps, and that no selection was 

 necessary to establish the type. 



2. "New forms spring laterally from the main stem." " The 

 current conception concerning the origin of species (or new 

 forms generally) assumes that species are slowly converted into 

 others. The conversion is assumed to affect all the individuals 

 in the same direction and in the same degree. . . . The birth 



1 De Vries, Species and Varieties, etc., pp. 558-575. These laws, while 

 announced for the evening primrose, are without doubt of wide if not general 

 application. 



