GENERAL IDEAS. 583 



museums of Paris, London,, Berlin, and Vienna, the number of known 

 species would scarcely extend to one-fourth of this. M'Leay and 

 Latreille consider 100,000 to exist already in cabinets, yet I much 

 doubt whether a positive calculation of them would give so many 

 species. Count Dejean in Paris, whose collection is known to be the 

 richest private one, calculates the number of his beetles at 21,000, and 

 in the Berlin collection, according to a general computation, there are 

 about 28,000 beetles. The beetles stand in proportion to all the other 

 insects in the ratio of two to three, consequently the Berlin Museum 

 should therefore possess about 78,000 species, a number which is not, 

 however, attained, because, as every one knows by experience, the 

 beetles are more anxiously sought by travellers than the other insects. 

 Hence I believe the number of known species in collections may be 

 considered at 80,000, which is certainly not too few, but many more 

 would not certainly be found. Of these there may be 36,000 beetles, 

 12,000 Lepidoplera, 12,000 Hymetioptera, 10,000 Diptera, 4,000 

 Hemiptera, 1,000 Orthoptera, 1,000 Neuroptera^ and 2,000 Dictyo- 

 toptera, including the parasitic Mallopkaga. Taxonomy instructs us 

 in the division, determination, and the description of these species, as 

 well as furnishes us with the history of all preceding arrangements. 



319. 



Every division and grouping of natural bodies has for object the 

 easier survey of the whole, and thus to facilitate the knowledge of all by 

 a course easier than the study of the separate individuals. Proceeding 

 from a somewhat different point of view, their division has for object to 

 render the discovery of any individual more easy from certain deter- 

 minate and essential characters, and this can be attained only by the 

 arrangement of the characteristic marks found in all natural bodies. 

 We thus obtain a classification which commences with the most general 

 characters, whence, proceeding to other more limited characters, the 

 groups are formed, which must be strictly exclusive, if the utility of 

 the subdivision is to be preserved. By means of such generally- 

 opposed groups, the list then gradually descends to the lowest of all, 

 the species, and with the definition of which its purpose is fulfilled. 

 We call a division made upon these principles artificial or an artificial 

 system, yet unjustly so, for a system can never be artificial, but must 

 be necessary and natural. A second point of view proceeds from the 

 idea that in nature there is a concatenation of beings in every direction; 



