PRINCIPLES OF SCIENTIFIC ARRANGEMENT. 127 



species are the last but combining element of all, al- 

 though their most remote members. The whole system 

 is an ingenious contrivance for breaking down a com- 

 plex multiplicity of characters, to simplify the means of 

 reaching all the collateral or adjacent species, that we 

 may be able to determine identity or difference. 



Entomology, and indeed natural history generally, 

 uses three words, very much alike, but very different in 

 signification and application. These are, habit, habits, 

 and habitat. The habit is that peculiar character of 

 identity, that je ne sais quoi, which marks all the species 

 of a genus collectively, and which, in some cases, only 

 the trained eye can detect. It is then seen instantane- 

 ously, and forcibly illustrates the extreme precision the 

 study of the natural sciences tends to cultivate. Their 

 utility, also, as a discipline to the mind, conjunctively 

 with the keen accuracy which practice gives the sight, are 

 qualifications not lightly to be esteemed. 



It is from such absolute control of detail that the 

 most efficient power of generalizing emanates, which, 

 when it has once become habitual, gives, from its rapi- 

 dity, an almost instinctive facility, as its inevitable con- 

 comitant, for both synthetical and analytical survey. 

 The mind thus becomes strengthened by vigorous exer- 

 cise, and has always, for every purpose, a powerful in- 

 strument at command, often used unconsciously, but 

 always effectively. Thus is habit, once correctly per- 

 ceived, ever retained. 



The habits are the peculiar manners and economy of 

 a species ; and the habitat is the kind of locality the 

 creatures affect, such as hill or plain, wood or meadow, 

 forest or fell, hedgebank or decaying timber, sand or 

 chalk or clay, and ground vertical or horizontal; and the 



