16 NOMENCLATURE. 



Our genera are constantly modified, and all we can do to define them is 

 to state the limits within which we understand a genus ; hence the difficulty 

 of applying the rules of priority to generic names where the limits are so 

 uncertain. The daily increasing list of specific and generic synonymes 

 but too plainly tells the tale of our ignorance. Are we to attempt to 

 define with mathematical accuracy what we mean by a species because 

 we find it convenient to use a binomial nomenclature to express zoological 

 units? As well attempt to solve an equation of an infinite number 

 of unknown quantities by means of an equation of the second degree. In 

 our nomenclature the best we can do at the present time is, by the examina- 

 tion of original specimens, to ascertain what are the limits at any time of 

 what we mean by a certain binomial combination, and to express these limits 

 by our synonymes. The fact is, that we can no longer define species as lias 

 been customary, and, with all descriptions, their value to other observers 

 depends generally upon the amount of material at the command of the de- 

 Bcriber and of the reader. How can we enable others to ascertain what we 

 mean? Scanty materials from few localities seem to limit a species within 

 narrow limits, and no difficulties appear. But take an example of one of 

 the most widely distributed species. — Hippon. variegata, found in Japan, 

 the Sandwich Islands, Indian Ocean, east coast of Africa, the Red Sea, — and 

 the diagnosis of the species will be very different if based upon material 

 limited to any one locality, or perhaps upon African, or Japanese, or Sand- 

 wich Islands specimens only, and we find them appear as Hipponoe sub- 

 coerulea or pentagona, or Hipponoe violacea and nigricans. 



A large number of systematic Zoologists claim the necessity of recognizing 

 geographical varieties by means of binomial names or of some kind of nota- 

 tion. What greater claim have they to be recognized than other categories, 

 which are all members of the same species? The part these geographical 

 species play in the limitation of Marine Fauna; is important, and the 

 limits of our geographical subdivisions are closely linked with our inter- 

 pretation of species ; we cannot lose sight of the question of geographical 

 variation any more than we can lose sight of the question of growth of an 

 individual. But because geographical differences have received certain spe- 

 cific names before their connection was traced through intermediate grada- 

 tion from many localities, must we for that reason retain this historical fact, 

 any more than we are justified in retaining as a specific name the name of 

 an animal which has afterwards been shown to be the young stage of one 



