ters are inherited. Mutations are not necessarily large, 

 many are smaller than the differences between extreme 

 fluctuating variants. DeVries ' species are termed Elemen- 

 tary Species. The Linnaean species of the systematist are 

 artificial groups, and not those presented by nature. 

 Such natural species do arise in the garden and m agricul- 

 tural practice, as shown by DeVries. As presented by De- 

 Vries 1 the Mutation Theory is not an alternative theory 

 to Natural Selection, but a supplementary hypothesis. 

 "The special problem which the Mutation Theory seeks to 

 explain is the manifold diversity of specific forms." 



According to the Mutation Theory the struggle for life 

 occurs among species, as well as among individuals. Nat- 

 ural Selection of species brings about a survival of the fit- 

 test species, eliminating some and protecting others. In 

 this way Natural Selection "guides the development of the 

 animal and vegetable kingdom." 



(a) — DeVries' Experiments 



(Consult DeVries' Species and Varieties) 



The importance of DeVries' experiments lies in the 

 application of the experimental method to the question of 

 the origin of specific characters. "The solution of this 

 problem," he said, "must be sought among the facts 

 themselves." He actually observed the origin of new 

 plant forms of the value of elementary species. He 

 discovered and propagated (1886-1900) a series of mu- 

 tations from Lamarck's Evening Primose Oenothera 

 lamarckiana — a plant growing wild near Amsterdam. 

 (Fig. 11). About 50,000 plants were cultivated, and of this 

 number 800 were found to differ distinctly from the parent 

 species, and to reproduce their characteristics constantly on 

 self-fertilization. More than twelve distinct types or 

 species were recognized by DeVries in these 800 variant 

 forms. The following table shows clearly the result of the 

 eight generations of a mutating strain of Lamarck's Even- 

 ing Primose, and the number of forms belonging to the 

 main new species discovered: 



(1) — DeVries is Professor of Botany in the University of Amsterdam 

 and Director of the Botanical Garden. His researches thirty 

 years ago on osmosis in plants gave him a high reputation among 

 plant phsiologisls. He has travelled and lectured extensively in 

 America, and has written several valuable works. (See Litera- 

 ture). 



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