114 
MOLLUSCA. 
Some species are remarkable for the long pedicle which supports 
them*. 
FAMILY II. 
AGGREGATA. 
The second family consists of animals more or less analogous 
to the Ascidiae, but united in a common mass, so that they 
seem to communicate organically with each other, and in this re- 
spect to connect the Mollusca with the Zoophytes ; but independently 
of their peculiar organization, these animals, according to the observa- 
tions of Messrs. Audouin and Milne Edwards, at first live and swim 
separately, only becoming united at a certain subsequent period, a 
fact which is in direct opposition to this opinion. 
Their branchiae, as in the Ascidiae, form a large sac, traversed by 
the aliment before it arrives at the mouth ; their principal ganglion 
is also situated between the mouth and the arms; a nearly similar 
disposition obtains with respect to the viscera and ovary f. 
Notwithstanding this, some of them, like the Biphora, have an 
opening at each extremity. Such is the 
Botryllus, GcBrt., 
Of an oval form, fixed on various bodies, and united by tens or 
twelves, like the rays of a star. The hrianchial orifices are at the 
The xiscidia canina, Miill., Zool. Dan., Iv, Asc. intestinalis, Bohatsch, X, 4, and 
perhaps even the .dsc. ^jafuZa, Mull., Ixv, and A. corrugata, Id., Ixxix, 2, appear to 
form but one species. There are also some interversions of synonymes, .and the 
species, generally, are far from being well ascertained. 
M. de Savigny has endeavoured to subdivide the Ascidiae, Mem. sur les Anim. 
sans, vert., part II, 1S16, into several subgenera, such as, 
1st. The Cynthi.e, whose body is sessile, and branchial sac longitudinally pli- 
cated ; their envelope is coriaceous ; 
2d. The Phai:.lusi.e, which differ from the Cynthiae in the branchial sac, which is 
not plicated ; their envelope is gelatinous ; 
3d. The Clavellin.e, whose branchial sac is without plicae, and does not pene- 
trate to the bottom of the envelope, and whose body is supported by a pedicle ; their 
envelope is gelatinous ; 
4th. The Boltenia, whose body is pediculate, and the envelope coriaceous. 
He also takes into consideration the number and form of the tentacula which 
internally surround the branchial orifice, but these characters, which are partly 
anatomical, cannot be applied with certainty to a great number of species. 
M. Macleay (Lin. Trans., XIV^, part III) establishes two more, Cystingia and 
Dei«brodoa, founded on similar characters. 
* Ascidia pedimculata, Edw., 356 ; and Asc. clavata, or Vorticella Bolfenii, Gm. 
f. It is to M. de Savigny that we are indebted for our recent knowledge of the 
singular organization of the whole of this family, formerly confounded with the 
Zoophytes, properly so called. At the same time, Messrs. Desmarets and Lesueur, 
made known the particular structure of the BotryUi and Pyrosoma. See the ex- 
cellent work of M. Savigny in his Mem. sur les anim. sans, verteb,, part II, fasc. I. 
