DE VRIES ON 'FLUCTUATIONS' 265 



I have considered these passages in some 

 detail because Dr. Shipley informs me that the 

 interpretation of de Vries's * fluctuations ' as non- 

 transmissible by heredity is based upon this 

 portion of the first volume of the Mutationstlieorie. 



(2) Speaking of the means by which the in- 

 dividual steps of evolution are brought about, 

 de Vries says : 



' On this point Darwin has recognized two possibilities. 

 One means of change lies in the sudden and spontaneous 

 production of new forms from the old stock. The other 

 method is the gradual accumulation of those always present 

 and ever fluctuating variations which are indicated by the 

 common assertion that no two individuals of a given race 

 are exactly alike. The first changes are what we now call 

 " mutations ", the second are designated as " individual 

 variations ", or as this term is often used in another sense, 

 as " fluctuations ". Darwin recognized both lines of evo- 

 lution ; Wallace disregarded the sudden changes and pro- 

 posed fluctuations as the exclusive factor.' * 



It has been abundantly shown in the present 

 volume (pp. 43, 44, 254-6) that de Vries is wholly 

 mistaken in ascribing to Darwin a belief in 

 evolution by mutation, and in maintaining that 

 there was in this respect any difference between 

 the two discoverers of Natural Selection. It is 

 amusing to observe the reason given by de Vries 

 for preferring the term * fluctuation '. May we 

 hope that he will abandon the word now that it 

 too ' is often used in another sense ' ? 



1 Hugo de Vries, Species and Varieties : their Origin by Mutation. 

 Second Ed., Chicago and London (1906), 7, 8. 



