ASCIDIZ. ~ 237 
The mouth is placed at the bottom of the branchial cavity ; 
this cavity penetrates near the bottom of the tunic, and at this 
part the mouth is placed. 
The mouth is a simple round aperture, which in some species 
is divided into grooves or short filaments, but has no lip or 
tentacles properly so called. 
The position of the mouth determines the position and the 
direction of the cesophagus, and that of the stomach. The 
cesophagus is short, and longitudinally plicated ; the stomach 
is simple, moderately dilated, with slightly elevated ridges, and 
its sides are pierced for receiving the bill: the intestine is sim- 
ple, without czeca, and has never more than one replication. 
They are nourished by very minute animals, that enter with 
the water into the branchial cavity. Cuvier has observed the 
débris of small Crustacea which had wounded the thin delicate 
tissue, which he therefore infers is not the natural food they 
generally feed on. 
The ovarium is situated between the reflection of the intestine 
with the liver; it is a granular whitish organ. The oviduct 
is generally very much undulated, and follows the course of the 
rectum, and terminates near its extremity : this position is very 
analogous to that in which the eggs pass behind the upper 
part of the branchiz in the Bivalves (Ginglymoconcha). 
The rectum terminates at the upper tube, and it is not im- 
possible that the seminal liquor passed by its excreting conduit 
very probably fecundates the eggs. : 
The part of the nervous system that is most visible consists 
of an oblong ganglion situated in the substance of the external 
tunic near the branchial tube ; it receives two branches from a 
nervous ring which encircles the cesophagus. The neryous 
system, according to Cuvier’s observations, varies in all the spe- 
cies that he has dissected: it will be evident to those who will 
look over the synopsis of the species that inhabit our seas, that 
the aperture of the mouth varies much in the notches, undu- 
lations, &c.; and if more minutely examined by dissection, 
they would at least form sections, and probably genera. 
