THE LOGIC OF DARWINISM 543 



of the occurrence of sterility between varieties, evidence which 

 he considered it " impossible to resist." There is therefore, in 

 point of sterility, no real distinction between genus, species and 

 variety and the objection fails. The classification of animals 

 and plants depends or ought to depend always on the number 

 and extent of the differences in that assemblage of characters 

 which constitutes the organism as a whole, the degree of sterility 

 constituting only one difference among many. 



It is probably in Darwin himself that the original source of 

 the error is to be found and I may fitly close my argument with 

 a condensed quotation from the Origin of Species which should, 

 I think, at the same time effect the final removal of any obscurity 

 about the point I have endeavoured to establish. The passage 

 occurs in Darwin's exposition of the principle which he " called 

 for the sake of brevity ' Natural Selection,' " in the summary of 

 the fourth chapter : " If organic beings vary at all in the several 

 parts of their organisation and if there be, owing to the high rate 

 of increase of each species, a severe struggle for life at some age, 

 season or year, it would be an extraordinary fact if no variation 

 ever had occurred useful to each being's own welfare in the 

 same manner as so many variations have occurred useful to 

 man. But if useful variations do occur, assuredly individuals 

 thus characterised will have the best chance of being preserved 

 in the struggle for life and from the strong principle of inherit- 

 ance they will tend to produce offspring similarly characterised." 

 I need hardly say, 1 do not quote this most moderate statement 

 for the purpose of dissent but my comment is this : that the 

 " many variations " which " have occurred useful to man " in 

 domesticated plants and animals are by that very fact " varia- 

 tions useful to each being's own welfare," since they have given 

 " the individuals thus characterised the best chance of being 

 preserved," as is shown by the fact of their preservation and 

 such individuals do " produce offspring similarly characterised," 

 so that the variations can be and have been accumulated from 

 generation to generation to produce an indefinite amount of 

 change. If this be so, the preservation of favoured races in the 

 struggle for life by means of Natural Selection and the con- 

 sequent production of new and more specialised forms widely 

 differing from the old is not a theory but an experimentally 

 proven fact. 



35 



