1S4 On Aquatic Carnivorous Coleoptcro. or Dtjtiscidie. 



than that of species; l)ut il" we suppo.se it to be answered in an affirmative sense^ 

 we may then treat these complex aggregates as themselves units, and study them 

 in the same way as we have supposed to be already done in the case of genera and 

 species. Looking at taxonomy in this aspect, species are the units of the classifier, 

 genera are aggregates of the fir.st degree, groups of genera aggregates of the second 

 degree, and so on. 



Whatever view be taken as to tlie nature of genera, it will at least be admitted that 

 there does not prevail among naturalists at present so great concord as to their 

 limits, as that which we find to exist about species. It is undoubtedly the case 

 that an attempt to define genera in a thoroughly natural manner is much more 

 difficult than the study of species ; while an additional obstacle is thrown in our 

 way by the fact that we are not yet acquainted with all existing species, so that 

 any da}^ by the discovery of a new and intei'mediate form two apparently distinct 

 genera may be connected together. 



This process of forming genera by synthesis — by the accord existing between 

 species as to the whole of their characters other than specific — has notwithstanding 

 its difficulties jirogressed in a more or less recognized manner, and is no doubt 

 destined to su])plant completel}' the process of ai'tificial classification; and there can 

 I think be but little doubt that the perfection of the miethod will be, for a while at 

 any rate, accompanifd liy an increase in the number of primary aggregates recognized 

 by zoologists. The enormous increase that has already occurred in the number of 

 genera has occasioned much discussion and given rise to considerable complaint 

 against those who make new genera ; and in point of fact the history of systematic 

 zoology pi-esents us with a picture of constant protest by the older naturalists 

 against the uuiltiplication of genera by their younger fellows. And it nuist be 

 admitted that the increase has indeed been enormous ; Linnseus only admitted 354 

 genera as composing the whole animal kingdom (" Systema NaturiB," Ed. xii) ; the 

 nuiuber at jiresent recognized could not be readily ascertained, but it is something 

 enoimous ; there are I believe about ten thousand genera recognized merely among 

 the beetles, and I anticipate that this number will increase to forty or fifty thousand. 

 I do not myself feel alarmed at this extraordinary nuiltiplication, but there is one 

 poini connected with it that is certainly to be regretted ; it is the corresponding 

 increase in the number of generic names ; the enormous growth in this I'espect has 

 already brought us to the unfortunate pass that few of us, even tliough we are 

 specialists, recognize, much less understand, the generic names even of the depart- 

 ment to M'hich we have given particular attention ; and thus the names of genera 

 come to have but little value. Seeing then how uncertain are the limits of genera 

 nt present, and iiow doubtful it is what kind of relation the genera we now adopt may 

 bear to those of the future when systematic zoology shall have assumed a more 

 periect form, we may Avell consider whether some method cannot be devised to 

 limit the incnnise of generic names, or at any rate to render their recognition a 



