WALLACE AND DARWIN. 81 



On the other hand, Darwin certainly inckided 

 large single variations (in other words, " varieties ") as 

 well as ordinary individual differences, among the 

 material for natural selection, and he did not abandon 

 the former until he was convinced by the powerful 

 reasoning of Fleeming Jenkin (North British Review, 

 June, 1867), who argued that single large differences 

 of a sudden and conspicuous kind (Darwin's " varia- 

 tions ") would certainly be swamped by intercrossing. 

 Upon this review of the " Origin " Francis Darwin 

 says (" Life and Letters ") — 



" It is not a little remarkable that the criticisms which my 

 father, as I believe, felt to be the most valuable ever made on 

 his views should have come, not from a professed naturalist 

 but from a Professor of Engineering." 



After reading this review, Darwin wrote to 

 Wallace (January 22nd, 1869):— 



"I always thought individual differences more important 

 than single variations, but now I have come to the conclusion 

 that they are of paramount importance, and in this I believe 

 I agree with you. Fleeming Jenkin's arguments have con- 

 vinced me." 



The ambiguity of this sentence evidently misled 

 Wallace into believing that the single variations were 

 considered of paramount importance. Darwin there- 

 fore wrote again (February 2nd) : — . 



" I must have expressed myself atrociously ; I meant to say 

 exactly the reverse of what you have understood. F. Jenkin 

 argued in the 'North British Review' (June 1867) against 



F 



