226 Mem. sur les Animaux sans Vertebres. (Marcn, 
We are not sufficiently acquainted with fishes to decide on the 
merits of that part of the subject; but it seems to be good, as far 
as we can judge. The disposition of the last eight classes is at least 
useful, if not partly natural: of the mammalia, with modifications, 
good ; and of the entomozoaires, decidedly unnatural, although it 
must be admitted that the separation of the setzpodes from the other 
vermes of authors is very much to be commended, and does infinite 
credit to the discernment of the author. 
—ie 
Il. Mémoires sur les Animaux sans Vertebres par J. C. Savigny. 
Seconde Partie. Mém.1\1—3. Recherches Anatomiques sur les 
Ascidies simples et composées, &c. 
We have already mentioned the splendid anatomical observations 
of Savigny, whose valuable work on the ascidie has at length 
reached us. 
The author has treated the subject under three heads of three 
memoirs. The first comprehends observations on gelatinous 
alcyonia with six simple tentacula, the animals of which have been 
confounded with polypes* by all preceding writers; but their 
structure is totally distinct. Their bodies have two distinct cavities ; 
they possess thoracic and abdominal viscera; they have an organ of 
generation; and the greater portion of them have beneath their 
external covering decided traces of a system of circulation. The 
rest of this memoir is occupied with details of their anatomical 
structure ; but as this part is not susceptible of condensation, we 
must refer such of our readers as cultivate this branch of zoology to 
the work itself, the whole of which is written in the usual clear and 
comprehensive style of its author. 
The second memoir contains observations of those alcyonia whose 
animals have two distinct openings, such as the botrill: and pyroso- 
mata, which have no external tentacula. 
The third memoir treats of the ascidie@ of authors, and contains 
several observations on the structure of those animals, as well as on 
the composed ascidie mentioned above. 
The heart is by no means very evident in the composed ascidie ; 
but on examining the various modifications presented in the diffe- 
rent genera of simple ascidie, no doubt can remain in the minds of 
those naturalists who do not reject analogical proof. ‘This organ is 
always situated close to the stomach, and the varieties of its form are 
infinite, and are fully detailed by Savigny. 
All the ascidi@, composed and simple, have a distinct nervous 
system, variously modified in the different genera, but always con- 
sisting of nerves and a large ganglion, considered as the brain, 
and which is brought into communication with the lateral ganglia 
* The polypes havea gelatinous body, with no other internal organ than a stomach 
with one opening, that serves the double purpose of mouth and anus,—LAMARcK. 
