PRINCIPLES OP 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 
