ASCIDIZ. Joo 
is alive, the serum secreted from the inner integuments) : it 
has an entire tunic with an exterior serous lamina, which con- 
tinues with the reflected membrane above mentioned ; its inner 
surface is composed of a muscular tissue with innumerable 
ramifications of nerves and veins; to this tunic the principal 
nervous ganglion adheres. 
The upper tube, which opens on the upper part of the sae, 
contains only the upper part of the branchial cavity, and has 
no communication with the other tube ; but its inner surface 
extends to the other tunic, which contains the extremities of 
the organs of generation and the rectum. 
All the viscera are enveloped in a peculiar peritoneum, and 
‘so is the heart im its pericardium ; hence the body, properly so 
called, is divided into three cavities; that of the branchie, 
which communicates with the upper aperture of the tube, at 
the bottom of which the mouth opens; that of the peritoneum, 
which does not communicate with the exterior by itself, but 
which is traversed by the intestinal tube, at which the com- 
mencement of the communication of the branchial cavity above 
by the rectum at the hinder tube, is short: the covering of 
the pericardium has no mediate or intermediate communication 
with its exterior. 
The branchial cavity is a large sac, which receives the water 
containing minute animals, on which it feeds, and which is 
afterwards rejected by the respiratory tube. 
It is very difficult to decide whether the respiratory openings 
are in the mouth or in the cesophagus. Cuvier thinks that 
the superior tube, and the pharynx or cardia, which has 
been termed the mouth, should retain that denomination more 
justly, because the same parts in the Oysters and in all the 
Bivalves have a similar orifice. 
The branchial cavity has a sort of neck or tube of introduc- 
tion, which is more straight than itself, in which the respiratory 
tissue does not extend; it is furnished with a range of fleshy 
filaments or very fine tentacles, which no doubt is to guide the 
animal to chase its food. ‘It is not impossible,” says Cuvier, 
“that on certain occasions the Ascidie reserve this orifice of 
