EXPERIMENTAL EVOLUTION 



III 



mutate. A plant that arises by mutation is an elementary 

 species, or mutant; and the theory that mutations (and not 

 fluctuations) explain the origin of the fittest, and supply 

 the materials upon which natural selection operates in the 



Extren 



Extreme. 



Mean 



FIG. 56. Diagram to illustrate the difference between fluctuating 

 variation and mutation; 0, original point of suspension; M, new point of 

 suspension after the mutation has occurred. 



formation of new species, de Vries called the mutation 

 theory. 



90. Examples of Mutation. The kohlrabi, cauliflower, 

 and other horticultural varieties of the wild cliff-cabbage 

 (Fig. 57), are believed to be mutants, and to have arisen, 



