330 STUDIES, SCIENTIFIC AND SOCIAL chap. 



due to use by the individual, is inherited, there can have 

 been no evolution. 



Now, I believe, and hope to be able to prove, that these 

 accumulated difficulties are almost wholly imaginary, and 

 arise from a neglect to consider known facts of variation 

 and known methods of adaptation. Mr. Spencer accepts 

 the fact that I and others have laid stress upon, that 

 individual variations are continually occurring in all parts 

 of the organism and in all directions,, and that the varia- 

 tions of each part are often independent of each other ; 

 but he ignores the equally undoubted fact that certain 

 parts are correlated, and very often do vary simultaneously. 

 The diagrams I have given in my Darwinism show this 

 clearly. A considerable number of parts, as the wings 

 and tail, tarsi and toes of birds, usually vary together, 

 either to the same or to a different amount ; but all of them 

 sometimes vary independently, and even in an opposite 

 direction to each other; and such irregular variations 

 evidently afford the very best material for natural selection 

 to work upon, since any kind of variation, either coincident 

 or independent, can be rapidly accumulated. This fact 

 alone does away with half of Mr. Spencer's difficulties. 



Another considerable portion of the supposed difficulties 

 is created by assumptions which pervade his articles but 

 which are opposed to the facts of nature. He tacitly 

 assumes that natural selection works by the preservation 

 of large individual variations — " sports " as they are often 

 termed ; whereas both Darwin himself and all his followers 

 entirely reject these as causes of modification of species 

 (except perhaps in rare cases where they may initiate 

 new organs), and rely wholly on those individual variations 

 which occur by thousands and tens of thousands in every 

 generation. Mr. Spencer continually uses such expres- 

 sions as, " This one has unusual agility " ; " that one 

 develops longer hair in winter " ; " another has a skin less 

 irritated by flies " ; " it is needful that the individual in 

 which it occurs shall have more descendants " ; "a varia- 

 tion . . . might sensibly profit the individual in which it 

 occurred " ; " would an individual . . . survive " ; " favour- 

 able variations . . . would disappear again long before 

 one or a few of the co-operative parts could be appro- 



