120 EVOLUTION 



and " individual variations." The former 

 correspond in a general way to what we 

 now call " discontinuous variations," " muta- 

 tions," " saltatory variations "; the latter to 

 " continuous variations " or " fluctuations." 

 Darwin was much interested in the former 

 class, " sports " as he sometimes called them; 

 but true to the influence of Lyell he came 

 deliberately to the conclusion that the minute 

 ubiquitous fluctuations were by far the more 

 important. The criticism of Fleeming Jenkin, 

 Professor of Engineering in Edinburgh, that 

 single large peculiarities would be likely to 

 be swamped by inter-crossing, had so much 

 weight with Darwin that he ceased to attach 

 importance to the larger divergences, and 

 found his raw material in the smaller fluctua- 

 tions. " The more I work," he said, " the more 

 I feel convinced it is by the accumulation of 

 such extremely slight variations that new 

 species arise." We shall return to this 

 question, but we may note in passing (1) that 

 there is no reason to believe that " single 

 variations " necessarily occur singly, the fact 

 being that numerous sports in the same 

 direction sometimes occur simultaneously; 

 (2) that some of the discontinuous variations 

 that have been studied have proved themselves 

 to have remarkable staying power in inherit- 



