250 NOMENCLATURE. 



still cause it to be employed in most cases for a short character- 

 istic description ; but the numerous minor points — especially 

 comparative characters now constituting the really essential 

 portions of the description, are usually given in the vernacular 

 of the author. Latin is not well adapted to the refinements of 

 modern species-making and its final disuse is probably not far 

 distant. Meantime the student is subjected to much inconve- 

 nience, unless his preparation embraces a useful knowledge of at 

 least the Latin, English, German, French and Italian languages. 



The Latin diagnosis, as now written, is usually worthless for 

 the purpose of identification. It is simply a ceremonial through 

 which the author becomes invested with the title to a specific 

 name ; it does not and cannot, and is not ordinarily intended 

 to define his property with sufficient accuracy to prevent tres- 

 pass on his rights by others ; therefore it becomes a trap for the 

 unwary and ambitious. On the other hand, the indefiniteness of 

 the usual diagnosis permits its author the greatest latitude in 

 shifting its object from species to species ; or, if he is enterpris- 

 ing, in capturing some of the species diagnosed at a later date 

 by his brother conchologists. 



It remains to define the meaning of the words species, variety, 

 genus, family, etc. 



All the specimens or individuals, which are so much alike that 

 we may reasonably believe them to have descended from a 

 common stock, constitute a species. A species, therefore, must 

 be capable of reproducing its like, subject to no other variations 

 than those occasioned by the slow openUion of changes of 

 environment, food, etc. For the old idea of the immutability of 

 species, each specially created in its present form, must.be 

 substituted that of practical immutability at a given period. 

 Whilst some species have preserved their characters intact since 

 the tertiary epoch, others show a gradual evolution of characters, 

 distinguishing them from their common progenitor. Forms 

 differing from specific types in an inferior degree may fall within 

 the range of individual variation, and their characters, individual 

 only, return to the parent stock ; or, the combined operation of 

 the laws of heredity, of selection, of environment may perpet- 

 uate in their descendants the differential characters and so, 

 according to the degree of development of these characters we 

 have varieties or new species. In fact varieties, conchologically 

 understood ; that is, possessing transmissable characters of 

 sufficient importance to require naming and description are 

 incipient species. Form, coloration and sculpture furnish the 

 principal characters of species, whilst genera are collections of 

 species possessing some more important character in common, 

 whether derived from the animal or shell. Subgenera possess the 

 essential generic character and in addition some character of 



