>^ 



162 ESSAY ON CLASSIFICATION. Part I. 



that he had fully satisfied himself of the real existence of such groups, for he 

 says distinctly in his Pldlosophia Botanica, sect. 169, " Scias characterem nou con- 

 stituere genus, sed genus characterem. Characterem fluere e genere, non genus 

 e charactere. Characterem non esse, ut genus fiat, sed ut genus noscatur." 



It is surprising that notwithstanding such clear statements, which might have 

 kept naturalists awake respecting the natural foundation of genera, such loose ideas 

 have become prevalent upon this subject, that at present the number of inves- 

 tigators who exhibit much confidence in the real existence of their own generic 

 distinctions is very limited. And as to what genera really are, the want of pre- 

 cision of ideas appears still greater. Those Avho have considered the subject at 

 all seem to have come to the conclusion that genei^a are nothing but groups 

 including a certain number of species agreeing in some more general features 

 than those which distinguish species; thus recognizing no difference between generic 

 and specific characters as such, as a single species may constitute a genus, when- 

 ever its characters do not agree with the characters of other sjjecies, and many 

 species may constitute a genus, because their specific characters agree to a certain 

 extent among themselves.^ Far from admitting such doctrines, I hoj^e to be able 

 to show that, however much or however little species may differ among themselves 

 as species, yet they may constitute a natural genus, provided their respective generic 

 characters are identical. 



I have stated before, that in order to ascertain upon what the different groups 

 adopted in our systems are founded, I consulted the works of such writers as are 

 celebrated in the annals of science for having characterized with particular felicity 

 any one kind of these groups, and I have mentioned Latreille as prominent among 

 zoologists for the precision with which he has defined the genera of Crustacea 

 and Insects, upon which he has written the most extensive work extant.^ An 

 anecdote which I have often heard repeated by entomologists who knew Latreille 

 well, is very characteristic as to the meaning he connected with the idea of genera. 

 At the time he was preparing the work just mentioned, he lost no opportunity 

 of obtaining specimens, the better to ascertain from nature the generic peculiarities 

 of these animals, and he used to apply to the entomologists for contributions to his 

 collection. It was not show specimens he cared to obtain, any would do, for he 

 used to say he wanted them only " to examine their parts." Have we not here 

 a hint, from a master, to teach us what genera are and how they should be 

 characterized ? Is it not the special structure of some part or other, which charac- 



^ Spring, Ueber die natui-historischen Begriffe ^ Latreillh, Genera Crustaceorum und Insect- 



von Gattung, Art und Abart, Leipzig, 1838, 1 vol. crura, Paris et Argent. 1806-1809, 4 vols. 8vo. 

 8vo. 



