an eclectic and picks that which will serve to advance his 

 work along the most fruitful lines. 



Almost any investigation of wide scope is in these days 

 an example of this improved attitude, but no other per- 

 haps illustrates so conclusively what may be called the 

 highest type of modern research as does the development of 

 the Mutation Theory first propounded by De Vnes. What 

 De Vries has really done is to bring within the range of 

 experimental proof certain questions which heretofore 

 have been regarded as matters of observation and specula- 

 tion alone. From this point, which might be said to have 

 had its origin in the acuteness of observation of the tax- 

 onomist and morphologist, the physiological trend has 

 ever increased until the last word in this discussion may 

 perhaps be for the physiologist alone. The great ques- 

 tion involved in the Mutation Theory is the old, old prob- 

 lem of the origin of species, a very considerable advance in 

 which has been made by De Vries and those who were stim- 

 ulated by his work. It is quite wrong to suppose that he 

 has controverted the general results of Darwin's work; he 

 has supplemented it, brought it within the range of more 

 conclusive proof. 



As the Linnaean or collective species may be regarded 

 today they are usually separable into several more or less 

 distinct strains which show no intergrading forms, and the 

 diagnosis of any one species is, so to say, the average im- 

 pression of them. To these distinct strains De Vries has 

 given the name elementary species, and according to his 

 interpretation they are the really discrete, finally segrega- 

 ble units, between which no intermediate types exist and 

 concerning the origin of which we are really concerned. 

 It matters not whether it was through ignorance or simply 

 from convenience that the earlier taxonomists grouped 

 many of these forms into a single species; we must con- 

 clude, that in general species, as recognized by the books, 



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