320 ON THE ANATOMY AND DEVELOPMENT OF PYROSOMA 
the following species, where these four animals seem to be the 
representatives of the four little foetuses which are developed in the 
egg before its extrusion.” 
The Pyrosomata paniculata are species in which the animals are not 
verticillate, and form very irregular circles, whose apices are every- 
where irregularly projecting. This division comprises P. gzgantenm 
and P. atlanticumt. 
Pyrosoma giganteum has an almost cylindrical body, the external 
tuberosities being very unequal, hemispherical or conical ; the most 
projecting having their appendage or terminal papilla lanceolate, 
subcarinate, and finely denticulated. The opening of the tube is 
commonly narrowed by an annular diaphragm. The total length of 
the largest tube is 14 inches; the opening, including the diaphragm, is 
2 inches across; the individuals vary in size from 3-5 lines, according 
as the neck of the thorax is more or less prolonged—a circumstance: 
which is independent of the age of the individual. 
The Pyrosomata of this species presented several varieties :— 
a. Body strongly stained with brown, as well internally as. 
externally, apparently in consequence of a brown substance filling 
the branchial cavities. Terminal papillae wide, and for the most part 
obtuse. Diaphragm very narrow, and leaving a large aperture. 
Total length 13-14 inches. 
&, Body bluish or a little violet, perfectly transparent. Papilla- 
very narrow. No annular diaphragm at the aperture, which presented. 
only very young individuals. Total length 6 inches. 
c. Body bluish, perfectly transparent, Papillae longer and more 
pointed than in the preceding varieties. An annular diaphragm, 
leaving but a very narrow aperture, around which almost all the 
animals were adult. Total length 5, 6, 7 inches. 
This species inhabits the Mediterranean and Atlantic, bordering 
the French coasts. 
In the description of Pyrosoma giganteum, Savigny gives some 
particulars not mentioned in his account quoted above. Thus, he 
says that the tunic offers but few vessels, “except upon the diaphragm 
which surrounds the aperture.” The tunic is provided “below the 
abdomen with two transverse muscles, and, besides, is marked by 
interlacing muscular nervures, which are very fine, and hardly visible. 
with a strong lens. ..... The festooned membrane at the entrance. 
of the branchial sac would be exactly circular if its posterior and 
inferior edge were not prolonged into a point. 
“Branchie wholly separated behind, divided in front as far as 
their bases, rounded or acuminated at their apices ; transverse vessels. 
