THE ZOOPHYTES, OR ANIMALIA RADIATA. 437 
or suck, and digest in an interior cavity, are assuredly animals 
in every sense of the word. 
The greater or less degree of complication of the zoophytes 
has given occasion to their division into classes; but as we 
are not yet perfectly acquainted with all the parts of their 
organization, these classes cannot be characterized with as 
much precision as those of the preceding divisions. 
The echini, and asteriz, to which the spines that they are 
usually furnished with, have caused Bruguiéres to apply the 
name of ECHINODERMATA, have a distinct intestine, floating 
in a large cavity, and accompanied with several other organs 
for generation, for respiration, and for a partial circulation, 
It has been found necessary to unite to them the holothuriz, 
which have an analogous internal organization, perhaps even 
still more complicated, although they have no moveable spines 
on the skin. 
The INTESTINAL WoRMsS, which form the second class, 
have no very evident vessels in which a distinct circulation 
might be carried on, nor separate organs of respiration ; their 
body is, in general, elongated or depressed, and their organs 
disposed longitudinally. ‘The differences in their nutritive 
system will probably cause them one day to be divided into 
two classes, which we already indicate by establishing two 
orders. In fact, in some there is an alimentary canal sus- 
pended in a true abdominal cavity, which is wanting in the 
others. 
The third class comprehends the ACALEPH2, or sea-nettles. 
They also have neither true circulating vessels, nor organs of 
respiration. Their form is generally circular, and radiating, 
and the mouth almost always serves as anus. They differ 
from the polypi only in a greater development in the tissue 
of their organs. The hydrostatic acalephe, which we leave 
at the end of this class, may, probably, at some future 
time, constitute a separate one when they shall be better 
