HYDROSTATICA. 429 
globules, and finally, partly filiform and susceptible of considerable 
elongation, form a cluster or garland at the inferior extremity *. 
Hippopus, Quoy and Gaym., 
Where there are merely lateral vesicles, almost semi-circular, or 
shaped like the foot of a horse, and crowded into two ranges, thus 
forming. a sort of spike comparable to that of certain grasses, from 
which also depends a kind of garland that crosses all the preceding 
parts. The united contraction of these vesicles enable the animal to 
move rapidlyt. In 
CuPuLiTa, 
The vesicles are reguiarly attached to the two sides of a frequently 
yery long axis f. 
Racemipa, Cwv., 
Where all the vesicles are globular and small; each one is furnished 
with a little membrane, and they are united in an oval mass which 
moves by their joint contractions §. 
Ruizopuyza, Peér., 
Where there are no lateral vesicles, but merely a superior bladder and 
an elongated stem, along which the tentacula are suspended, some 
conical and the others filiform ||. The 
StrerHanomisa, Per., 
Appears to be a third combination, where the lateral bladders, which, 
in Physsophora proper, adhere to the top of the stem above the ten- 
tacula, extend along its length and intermingle with tentacula of 
various forms 4. 
It is directly after these hydrostatic Acalepha that we may place the 
Drenyes, Cuv., 
A very singular genus, where two different individuals are always 
found together, one encased in a cavity of the other, but susceptible of 
being separated without destroying the life of either. They are ge- 
* Such is the Physsophora hydrostatica, Gm. The individual named Phys. muso- 
nema, by Pér., Voy. XXIX, 4, is well preserved; that of Forskahl, Ic., XXXIII, 
E, e, 1, e, 2; Encyc.. LXXXIX, 7, 9, appears to be the same species, but deprived 
of a portion of its tentacula, which are easily removed. I also think that the Phys> 
sophora rosacea, Forsk., XLIII, B, b, 2, and Encye., LXXXIX, 10, 11, is a muti- 
lated specimen of another species. 
Add Rhizophysa Chamissonis, Fisenh., Medus., Ac. Nat. Cur. X, pl. 35, f. 3;— 
Rhiz. helianthus, and Rhiz. melo, Quoy and Gaym., Ann. des Sc. Nat., X., pl. 5, and 
many other undescribed species. 
+ Quoy and Gaym., An. des Se. Nat. X, pl. 10, 4, A, f. 1—12. 
N.B. The Glebe of Otto, Ac. Nat. Cur., XI, p. II, pl. 42, f. 3, is merely a vesicle 
of a Hippopus. 
+ Voy. de Freycin., Zool., pl. 87, f. 15. 
§ A new genus from the Mediterranean. 
|| Physsophora filiformis, Forsk., XXXIII, F; Encyce., LXXXIX, 12; the same as 
the Rhizophyza planestoma, Pér., Voy., XXIX, 3. MM. Quoy and Gaymard, how- 
ever, think that these Rhizophyze are merely Physsophore which have lost their 
lateral bladders. 
{ Stephanomia Amphitritis, Péron, Voy., XXIX, 5. The Stephanomia uvaria, 
Lesueur, appears to me to approximate nearer to Physsophora proper. 
