ACEPHALA NUDA. 431 



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(l). 



A smaller species is also known(2) where the animals are 

 arranged in very regular rings. 



The remainder of these aggregated Mollusca, like the ordi- 

 nary Ascidise, have the anus and branchial orifice approximated 

 to the same extremity. The species known are all fixed, and 

 till now they have been confounded with the Alcyonia. 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(3). 



Some of them are extended over bodies like fleshy crests(4). 



Others project in a conical or globular mass(5), 



Or expand into a disk comparable to that of a flower or of an 

 Actinia(6), or are elongated into cylindrical branches supported by 

 slender pedicles, &c.(7), or form parallel cylinders(8). 



Recent observations even seem to show that the Eschars, hitherto 

 placed among the Polypi, belong to this family of the Mollusca(9). 



(1) Several of the PolycUna and ApUdia of Savig'ny. 



(2) Pyrosoma atlanticum, P^ron., Ann. du Mus., IV, Ixxii; Pyrosoma gigas, 

 Desmar., and Lesueur, Bullet, des So. June 1815, pi. v, f. 2. 



(3) The Pyrosome elegant, Lesueur, Bullet, des Sc, June 1815, pi. v, f. 2. 



(4) It is from the number of strangulations, that is to say, tlie greater or less 

 separation of the branchiae, stomach and ovary, that M. de Savigny has formed his 

 PoLYcuNUM, Aphdium, Didemmum, Euc^ium, Diazona, SiGiiLiNA, &c. whicfa, 

 in our opinion, need not be retained. Here, also, should come the Mcyonium 

 Jicus, Gm.; the Distomus variolosus, Gsertn., or Mcyonium ascidiotdes, Gm., Pall., 



Spic. Zool., X, iv, 7. 



(5) The Eucoelium, Savig.; the Distomi are arranged in the same manner. 



(6) The genus Diazowa, Sav., consisting of a large and beautiful purple species 

 discovered near Ivice by M. Delaroche. 



(7) The' genus Sigillina, Sav., whose cylindrical branches are frequently a foot 

 long, and the animals, slender as threads, but three or four inches. 



(8) The genus Synocium, Lam. 



(9) Messrs Audouin and Milne Edwards on the one hand, and M. de Blainville 

 on the other, have lately verified this fact, which the obsei'vations of Spallanzani 

 previously seemed to announce. 



