2g DEFINITION OF THE TERM INSECT. 
insufficient. In common language, not only the tribes 
above mentioned, but most smal/ animals—as worms, 
slugs, leeches, and many similar creatures, are known by 
the name of znsects. Such latitude, however, cannot be 
admitted in a scientific view of the subject, in which the 
class of insects is distinguished from these animals just 
as strictly as beasts from birds, and birds from reptiles 
and amphibia, and these again from fishes. Not, indeed, 
that the just limits of the class have always been clearly 
understood and marked out. Even when our corre- 
spondence first commenced, animals were regarded as 
belonging to it, which since their internal organization 
has been more fully explained, are properly separated 
from it. But it is now agreed on all hands, that an 
earthworm, a leech, or a slug, is not an insect; and a 
Naturalist seems almost as much inclined to smile at 
those who confound them, as Captain Cook at the island- 
ers who confessed their entire ignorance of the nature of 
cows and horses, but gave him to understand that they 
knew his sheep and goats to be birds. 
You will better comprehend the subsequent definition 
of the term Jnsect, after attending to a slight sketch of 
the chief classifications of the animal kingdom, more 
cx especially of the creatures in question, that have been 
proposed. That of Aristotle stands first. He divides 
animals into two grand sections, corresponding with the 
Vertebrata and Invertebrata of modern Zoologists: those, 
namely, that have blood, and those that have it not?:— 
by this it appears that he only reg>rded red blood as 
real blood; and probably did not suspect that there was 
a true circulation in his Mollusca and other white-blooded 
* Evasue, Avasue. Hist. Animal. 1.i. c. 6. 
: > ‘ ~ Pa ARs 
