DARWIN AND HIS REVIEWERS. 165 



upon different patterns of form, and embrace representatives 

 equally independent in their origin ; that genera are founded 

 upon ultimate peculiarities of structure, embracing representa- 

 tives which, from the very nature of their peculiarities, could 

 have no community of origin; and that, finally, species are 

 based upon relations and proportions that exclude, as much as 

 all the preceding distinctions, the idea of a common descent. 



" As the community of characters among the beings belong- 

 ing to these different categories arises from the intellectual con- 

 nection which shows them to be categories of thought, they 

 cannot be the result of a gradual material differentiation of the 

 objects themselves. The argument on which these views are 

 founded may be summed up in the following few words: 

 Species, genera, families, etc., exist as thoughts, individuals as 

 facts." ' 



An ingenious dilemma caps the argument : 



" It seems to me that there is much confusion of ideas in 

 the general statement of the variability of species so often re- 

 peated lately. If species do not exist at all, as the supporters 

 of the transmutation theory maintain, how can they vary ? and 

 if individuals alone exist, how can the differences which may be 

 observed among them prove the variability of species? " 



Now, we imagine that Mr. Darwin need not be 

 dangerously gored by either horn of this curious di- 

 lemma. Although we ourselves cherish old-fashioned 

 prejudices in favor of the probable permanence, and 

 therefore of a more stable objective ground of species, 

 yet we agree and Mr. Darwin will agree fully with 

 Mr. Agassiz that species, and he will add varieties, 

 " exist as categories of thought," that is, as cognizable 

 distinctions which is all that we can make of the 

 phrase here, whatever it may mean in the Aristotelian 

 metaphysics. Admitting that species are only cate- 



1 In American Journal of Science, July, 1860, p. 143. 

 8 



