270 APPENDIX D 



need to base our proofs upon inference, for Prof. 

 Davenport makes the following clear statement : 



* Does the breeder actually introduce new characters into 

 the organic world by summating fluctuations? De Vries 

 insists that the improvement that follows selection nearly 

 or wholly ceases after four or five generations, and if selection 

 be abandoned the race rapidly returns to its primitive 

 condition.' 1 



The two following passages are quoted from 

 Mr. K.H. Lock's book 2 : 



(1) ' There are some, including de Vries, who regard all 

 fluctuating variations (individual differences) as being of the 

 nature of acquired characters, and as being at the same time 

 capable of hereditary transmission, although de Vries 

 believes the amount of progress possible in this way to be 

 strictly limited.' (p. 75 ; see also the passage quoted from 

 Mr. Lock on p. 262.) 



(2) ' The actual effect of this kind of selection is well 

 illustrated by the results of the processes employed in the 

 sugar-beet industry, in which elaborate care is taken to 

 select those roots which contain the highest percentage of 

 sugar for the purpose of propagation. This process was 

 followed at first by a rapid improvement, but the rate at 

 which the percentage of sugar increased soon fell off, until 

 at the present day all that selection can effect is to keep up 

 the standard of excellence already attained. 



* * * 



' There is no reason to doubt that a thoroughly efficient 

 method of selection would have worked its full effect in 

 a few generations. 



* * * 



'From his own experiments, de Vries has come to the 

 conclusion that, when selection is really efficient, the full 

 possible effect of this process is exhausted in quite a small 



1 Fifty Years of Darwinism, New York (1909), 173-4. 



2 Variation, Heredity and Evolution. London, 1909. Second Ed. 



