SPECIES A TERM, NOT A FACT. 113 



of systematic botany."* " We have agreed," says 

 Bicheno, " that a species shall be that distinct 

 form, orginally so created, and producing, by cer- 

 tain laws of generation, others like itself. There 

 is this inconvenience attending the use of it by 

 naturalists, that it assumes as a fact, that which, 

 in the present state of science, is in many cases a 

 nt subject of inquiry ; namely, that species, ac- 

 cording to our definition, do exist throughout 

 nature. It is too convenient a term to be dis- 

 pensed with, even as an assmnption ; only care 

 should be taken that we do not accept the abstract 

 term for the fajctr\ Mr. Westwood, speaking of 

 insects, says, " In ver}- extensive genera, the dis- 

 tinctions of species are so minute, that it requires the 

 most practised eye to separate them ; and, indeed, 

 there are some groups, the species of which are so 

 intricately blended together, that no two entomo- 

 logists are agreed as to their distinctness." Ac- 

 cording to Mr. Haldeman, author of a learned work 

 on the fresh-water mollusks of America, " There 

 are distinct species in that class — among the 

 Unionidae, for example, [and this is a remark 

 applicable to other departments of the animal 



* Magazine of Zoology and Botany, i. 116. 

 f Linnsean Transactions, xv. 482. 



