52 
SUPPLEMENT 
diately to follow the Crustacea, and conduct to the insects ; 
but, in consequence of their form, of the trifling development 
of their organs of locomotion, and especially in consequence 
of the mode of respiration in insects, which appears to hold 
the place of the circulation of the blood, he thinks that the 
worms ought to be placed between the insects and the zoo- 
phytes ; that is, between the class myriapoda, with which 
he finishes the former, and that of Helminthii, or intestinal 
worms, with which he commences the latter. 
M. de Blainville intended to place this class between the 
myriapoda and the apoda, or intestinal worms. Thus we 
should pass, almost insensibly, to the sub-annelida, and by 
them to the holothurise, which would properly commence the 
zoophytes. But it was necessary to place between those two 
types the mollusca, which, after the vertebrated animals, also 
form a parallel line, proceeding to, and arriving at the zoo- 
phytes, through the ascidim. 
Respecting the animals of which we are now writing, there 
is but little of any thing important in the study of them, ex- 
cept what may be derived from it by natural philosophy. 
Their utility to the human species is but slight indeed. The 
larger nereides and the arenicolm are, however, much used as 
baits for catching fish, especially whiting and mackerel. They 
even constitute a small object of commerce w r ith the inhabit- 
ants of the coasts of the Atlantic and the Mediterranean. The 
lumbrici, or earth-worms, are also employed to catch fresh- 
water fish, and among others, eels, and fish in general, that 
live in mud. 
We must, however, now take a brief view of the organiza- 
tion of the chetopoda. 
The organization of these animals has been studied in its 
external parts by Pallas, by Muller, and very particularly by 
Otho Fabricius, and M. Savigny. As to their internal organi- 
