oe INTRODUCTION. 
from the circulation in closed vessels to nutrition by imbibi- 
- tion, and the corresponding one of respiration in circumscribed 
organs, to that effected by trachex or air-vessels distributed 
throughout the body. In them, the organs of taste and sight 
are the most distinct; one single family alone presenting that 
of hearing. Their jaws, when they have any, are always 
lateral. 
The fourth form, which embraces all those animals known 
by the name of zoophytes, may also properly be denominated 
Animaha Radiata, 
Or radiated animals. We have seen that the organs of 
sense and motion in all the preceding ones are symmetrically 
arranged on the two sides of an axis. ‘There is a posterior 
and anterior dissimilar face. In this last division, they are 
disposed like rays round a centre; and this is the case even 
when they consist of but two series, for then the two faces 
are similar. They approximate to the homogeneity of plants, 
having no very distinct nervous system or particular organs of 
sense; in some of them, it is even difficult to discover a ves- 
tige of circulation; their respiratory organs are almost univer- 
sally seated on the surface of the body, the intestine in the 
a _ greater number is a mere sac without issue, and the lowest of 
fee 7 the series are nothing but a sort of homogeneous pulp, endow- 
ae co with motion and peda (1) 
a) Before my time, modern naturalists divided all invertebrated animals into | 
? ‘two classes, me and Worms. I was the first who attacked this method ; and 
‘Voted te the characters and limits of the ane Crustacea, Insects 
.chinodermata and Zoophytes. In a memoir read before the Insti- 
the e Sst of December 1801, I ascertained the red-blooded worms or Anne-— 
' a ly, ina memoir read before the Institute in July 1812, and printed 
du Museum d’Histoire Naturelle, tome xix, I distributed these 
= diviions, each of which is pipe to a branch of Pa @ 
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-— ‘ ty * . ® 
