THE RAW MATERIALS OF EVOLUTION 99 



of Lyell he came to the conclusion that the 

 minute ubiquitous " individual variations " were 

 by far the more important. Fleeming Jenkin, 

 Professor of Engineering in Edinburgh, pointed 

 out that single large peculiarities would be likely 

 to be swamped by inter-crossing, and this criticism 

 had so much weight with Darwin that he ceased 

 to attach importance to the larger divergences, 

 and found his raw material in what he called 

 " individual variations." " 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." 



In reference to both sports and small variations, 

 Darwin used the terms " indefinite " and " spon- 

 taneous," to distinguish them from " definite 

 variations," which are now called somatic modifica- 

 tions i.e. definite and direct results of environ- 

 mental or functional changes. Darwin believed 

 in the occasional transmissibility of these " definite 

 variations," and in so doing he agreed with 

 Lamarck, whose work he does not seem to have 

 adequately appreciated. 



PROGRESS SINCE DARWIN'S DAY IN REGARD TO 

 VARIATION. While we must still confess, with 

 Darwin, that in regard to the causes of variation 

 our ignorance is immense, we have also to recognise 

 that, in several directions, there is progress to 

 report. For some time after the publication of 

 " The Origin of Species " more attention was 

 given to the directive than to the originative factors 

 in evolution. The idea of selection fascinated 

 naturalists, and it was too much the custom simply 

 to postulate variability to meet the demands of 

 particular problems. Life is so abundant and 



