EVOLUTION 



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natural selection. The work of De Vries has been important in 

 establishing this point of view. 



The Mutation Theory. — In 1886 Hugo de Vries, a Dutch 

 botanist, found a number of evening primroses, Oenothera 

 lamarckiana, growing wild in an abandoned potato patch at 

 Hilversum, Holland. The peculiar feature about these plants 

 was that in addition to the usual fluctuating variants there were 

 some discontinuous variants which De Vries called mutations. 

 On transplanting some of the typical lamarckiana plants to a 

 garden where he could keep them under observation, he found 

 that in the course of 7 generations, involving a total of some 

 50,000 plants, 5 or 6 different mutations, totaling about 800 

 plants, were produced from the parent stock (Table 2). Since 



Table 2. — An Eight-generation Pedigree Culture of Lamarck's 



Evening Primrose 



The giant mutant was obtained only once, but all the others, in at least three different 

 generations, from lamarckiana parents. (From Castle, "Genetics and Eugenics," Harvard 

 University Press.) 



the characters of the mutations were markedly different from 

 those of the typical Oenothera lamarckiana that produced them, 

 and since the mutant characters were inherited, De Vries believed 

 that he was witnessing the formation of new species at one single 

 step. 



De Vries was so impressed with the importance of mutation as 

 the method of evolution that he discounted Darwin's view of the 

 gradual accumulation of fluctuating variations under the guidance 

 of natural selection in the building up of new species. De Vries 

 believed that fluctuating variations are of no importance in this 

 connection because they are not inherited. Mutations, accord- 

 ing to De Vries, are due to changes of unknown cause in the germ 



