ON THE ANATOMY AND DEVELOPMENT OF PYROSOMA = 317 
foregoing species, and ought in consequence to be regarded as the 
corresponding region. The branchial cavity is very large; it occupies. 
those two-thirds of the tunic which lie nearest the circumference of the 
cylinder : its bottom, which is completely open, communicates freely 
with the other third, which lodges the viscera of the abdomen. These 
are small, and situated on the right side. The space which they leave 
unoccupied is commonly filled by the fcetuses, which successively 
arrive and are developed there, as we shall see below. The structure 
of the branchial sac in the Pyrosomata may lead one to believe that 
the water absorbed by the oral, makes its way out by the anal orifice. 
This would be a feature of resemblance with the Sa/e, in which it is. 
indubitable that the water takes this course. However this may be, 
the network which lines the cavity is otherwise organized: it is loose, 
and composed of fine, undulating, opaque white vessels, some of which 
are longitudinal, while others are transverse and cross the former at 
right angles—a character which is common to all the genera of this 
family. The network does not occupy the whole cavity, but only its two: 
lateral walls; so that there are obviously, in this genus, two separate 
and opposite branchiz, one on the right, and the other on the left, and 
which are much narrowed, and consequently distant, at the top. In 
the foregoing genera, the two branchie, although really distinct, are 
only separate behind. The pharynx is at the bottom of the branchial 
cavity, towards its upper angle. The cesophagus is curved sharply to 
be inserted into a notch of the stomach, which is placed behind the 
bottom of the branchial cavity. The stomach is fleshy, smooth,. 
compressed, ovoid, or slightly cordiform. The intestine, very delicate 
at its commencement, suddenly enlarges ; a short course brings it to 
the inferior edge of the tunic, where it receives the insertion! of a large 
organ analogous to the liver; afterwards it returns to the stomach,. 
behind which it ends in a simple and rounded anus. The feces are 
homogeneous, clear, yellow, and divided into little masses, the last of 
which is often already engaged in the atrial orifice (oscule anal), which 
seems to prove that the rectum has the power of elongating and of 
adapting itself to this orifice. 
“TI must remark, that the liver, or the organ which from its. 
position may be regarded as such, is attached to the intestine by a 
bundle of divergent canals; that it is rounded, commonly opaque, 
rose-coloured, yellow or brown, strangulated above its insertion, and 
divided into from eight to twelve ribs, by grooves which converge from 
its base to its apex; it is very soft, and may be broken up into-oblong 
pedunculated vesicles. I may add, as a remarkable fact, that, in. 
1 An error: the organ in question being the testis. 
