﻿260 Darwin y and after Darwin. 



brought to light, either as still existing or as having 

 once existed. Consequently, the more that such 

 knowledge increases, the more does our catalogue of 

 ' species " diminish. As Kerner says, " bad species " 

 are always multiplying at the expense of "good 

 species " ; or, as Oscar Schmidt (following Hackel) 

 similarly remarks, if we could know as much about 

 the latter as we do about the former, " all species, 

 without any exception, would become what species- 

 makers understand by ' bad species ' V Hence we 

 see that, just as Mr. Gulick could have created good 

 species by secretly destroying his intermediate 

 varieties, so has Nature produced her " good species " 

 for the delectation of systematists. And just as Mr. 

 Gulick, by first hiding and afterwards revealing his 

 intermediate forms, could have made the self-same 

 characters in the first instance necessarily useful, but 

 ever afterwards presumably useless, so has Nature 

 caused the utility of diagnostic characters to vary 

 with our knowledge of her intermediate forms. It 

 belongs to the essence of our theory of descent, that 

 in all cases these intermediate forms must either be 

 now existing or have once existed ; and, therefore, 

 that the work of species-makers consists in nothing 

 more than marking out the lacunae in our knowledge 

 of them. Yet we are bound to believe that wherever 

 these lacunae in our knowledge occur, there occurs 

 also the objective necessity of causation as utilitarian 

 — a necessity, however, which vanishes so soon as 

 our advancing information supplies the intermediate 

 forms in question. It may indeed appear strange that 



1 The Doctrine of Descent and Darwinism, Eng. Trans, p. 102. 



