THE METHOD OF ORGANIC EVOLUTION. 435 



of discontinuous variations, has been shown to be founded upon a com- 

 parison of thin<;:s of a totally dissimilar nature, and, further, to be 

 absolutely unintelligible and powerless unless in strict subordination 

 to natural selection. 



The reason why two writers of such extensive knowledge and 

 undoubted ability have so completely failed in dealing with the great 

 l)roblem of the modification of organic forms has beeu clearly indicated 

 during the course of this discussion. It has arisen from the fact that 

 they have devoted themselves too exclusively to one set of factors, 

 while overlooking others which are both more general and more funda- 

 mental. These are the enormously rapid- multiplication of all organ- 

 isms during more favorable i)eriods, and the consequent weeding out 

 of all but the fittest in what must be on the whole stationary popula- 

 tions. And acting in combination with this annual destruction of the 

 less fit is the periodical elimination under recurrent unfavorable con- 

 ditions of such a large proportion of each species as to leave only a 

 small fraction — the very elect of the elect — to continue the race. It is 

 only by keeping the tremendous severity of thig inevitable ami never- 

 ceasing process of selection always present to our minds and applying 

 it in detail to each suggested new factor in the process of evolution 

 that we shall be able to determine what part such factors can take in 

 the production of new species. It is because they have not done this 

 that the two authors whose works have been here examined have so 

 completely failed to make any real advance toward a more complete 

 solution of the problem of the origin of species than has been reached 

 by Darwin and his successors. 



