OTHER WRITERS ON 'FLUCTUATIONS' 271 



number of generations, and that then the only further effect 

 of selection is to keep up the standard already arrived at.' 

 (pp. 185-6.) 



Professor J. Arthur Thomson l in the first of 

 the following passages clearly states the germinal 

 origin of fluctuations, in the second correctly 

 expresses de Vries's conclusions : 



(1) ' . . . when we collect a large number of specimens of 

 the same age from the same place at the same time, we 

 often find that no two are exactly alike. They have peculi- 

 arities of germinal origin or, in other words, they show 

 individual or fluctuating variations.' (p. 78.) 



(2) 'Fluctuations do not lead to a permanent change in 

 the mean of the species unless there be a very rigorous 

 selection, and even then, if the selection be slackened, there 

 is regression to the old mean : mutations lead per saUum to 

 a new specific position, and there is no regression to the old 

 mean.' (p. 98.) 



I have brought perhaps unnecessarily ample 

 evidence in support of the fact that de Vries's 

 ' fluctuations ' are assumed by him to be trans- 

 missible by heredity, and that this assumption is 

 an essential element in the author's definition of 

 his technical term. When we remember that 

 they are just the 'individual differences' of 

 Darwin, and that de Vries's belief in their power- 

 lessness for continued evolution is based on Francis 

 Galton's well-known law of recession, it is really 

 waste of time to inquire whether they are trans- 

 missible. But such positive statements to the 

 contrary have been made by the most prominent 



1 Heredity, London, 1908. 



