Characters as Adaptive and Specific. 259 



allows that a species is "not a distinct entity," but 

 " an assemblage of individuals which have become 

 somewhat modified in structure, form, and consti- 

 tution"; while estimates of the kinds and degrees 

 of modification which are to be taken as of specific 

 value are conceded to be undefinable, fluctuating, and 

 in not a few cases almost ludicrously divergent. 



Perhaps one cannot more forcibly present the 

 rational value of this position than by noting the fol- 

 lowing consequences of it. Mr. Gulick writes me that 

 while studying the land-shells of the Sandwich Islands, 

 and finding there a rich profusion of unique varieties, 

 in cases where the intermediate varieties were rare he 

 could himself have created a number of species by 

 simply throwing these intermediate varieties into his 

 fire. Now it follows from the dogma which we are 

 considering, that, by so doing, not only would he 

 have created new species, but at the same time 

 he would have proved them due to natural selection, 

 and endowed the diagnostic characters of each with 

 a " necessarily ' adaptive meaning, which previously it 

 was not necessary that they should present. Before 

 his destruction of these intermediate varieties, he need 

 have felt himself under no obligation to assume that 

 any given character at either end of the series was 

 of utilitarian significance : but, after his destruction of 

 the intermediate forms, he could no longer entertain 

 any question upon the matter, under pain of being 

 denounced as a Darwinian heretic. 



Now the application is self-evident. It is a general 



fact, which admits of no denial, that the more our 



knowledge of any flora or fauna increases, the greater 



is the number of intermediate forms which are 



S 2 



