66 THE THEORIES OF EVOLUTION 



jects. One is the Russian botanist, Korshinsky, 

 whose theory of heterogenesis preceded by several 

 years De Vries's 9 theory ; the other is not a theorist 

 but a practical scientist, Luther Burbank, the well- 

 known California horticulturist. His work is of 

 capital importance and his conclusions are the more 

 interesting as he has had opportunity of experiment- 

 ing on a larger scale than had ever been done in that 

 department of research. 10 Luther Burbank states 



Vthat it is invariably a rich soil and favourable condi- 

 tions which determine the appearance of new vari- 

 ations, whereas underfertilised or overfertilised 

 ground induces reversion. 



Burbank refuses to draw any definite conclusions, 

 but we can easily draw our own: new variations 

 i appear, not where the life struggle is the fiercest, that 

 is, as Darwin believed, where conditions are most un- 

 favourable, but where the struggle is mildest, and 

 where all the wants of living things are filled. 



Starting from rather theoretical considerations, 

 Korshinsky arrives at the same conclusion as Bur- 

 bank. No new forms appear, he writes, under dif- 



~^> ficult conditions of life, or if they do appear, they very 

 soon become extinct. Their appearance is due to 

 certain organic disorders, especially to disorders of 



» See Chapter XX. 



10 See V. L. Kellogg's article in Popular Science Monthly, 1906, Vol. 

 LXIX, pp. 363-374. See also Kellogg's Darwinism To-day, p. 310 and 

 following. 



