130 CLASS ACEPHALA. 
The Mediterranean and the ocean produce large species, 
the animals of which are arranged with but little regularity. 
They exhibit a phosphorescent appearance during the night. 
Several of the polyclina and aplidia of Savigny. 
A smaller species is also known, where the animals are 
arranged in very regular rings. (Pyrosoma Allanticum, 
Peron, &c.) 
The remainder of these aggregated mollusca, like the 
ordinary ascidie, have the anus and branchial orifice approxi- 
mated to the same extremity. The species known are all 
fixed, and till now they have been confounded with the alcyo- 
nia. ‘The visceral bundle of each individual is more or less 
extended into the common cartilaginous or gelatinous mass, 
more or less narrowed or dilated in certain points ; but each 
orifice always forms a little six-rayed star on the surface. We 
unite them all under the name of 
POLYCLINUM. 
Some of them are extended over bodies like fleshy crests. 
Others project in a conical or globular mass. The euce- 
lium, Savig., the distomz, are arranged in the same manner. 
Or expand into a disk, comparable to that of a flower or of 
an actinia. (The genus diazona, Sav.) 
Or are elongated into cylindrical branches, supported by 
slender pedicles, &c. (The genus sigillina, Sav.) 
Or form parallel cylinders. (The genus synoicum, Lam.) 
Recent observations even seem to show that the ESCHAR®, 
hitherto placed among the PoLypt, belong to this family of 
the mollusca. 
ee 
