56 MOLLUSCA. 
Trans. vol. vii. 175.) Now, to what does all this attention 
of Linnzeus amount? In all the species which he has de- 
scribed, he has only noticed the animals of four of these, 
and in a very slight manner ; and, with regard to the name 
of the molluscous inhabitant which he included in his ge- 
neric marks, we hesitate not to say, that by this union he 
has betrayed carelessness. To many British ears these terms 
may sound harsh, but the proof of their correct application 
in the present instance will be abundantly evident, if we 
examine the references to the animals of a few of his ge- 
nera. The genus chzton is thus characterised ; “ Animal 
Doris. Testz plures, longitudinaliter geste, dorso incum- 
bentes.” Are we not led to conclude from this character, 
that the animals of the chiton exactly resemble the animals 
of the doris genus, with the addition of the shells? If this 
be the case, how artificial is that system which places these 
two genera in separate orders! Upon turning, however, 
to the genus doris among his vermes mollusca, we find the 
following characters assigned to it; “ Corpus repens, ob- 
longum, subtus planum. Os antice subtus. Anus postice, 
supra cinctus ciliis. Tentacula duo, supra corpus antice 
intra foramina retractilia.” Now, the fine fringes around 
the anus of the doris, which are the branchie of the animal, 
and form the essential character of the genus, are not to be 
found in the animals of the chiton, whose branchiz are in 
the form of leaves placed along the margin of the body, and 
the anus is a simple pore. 
According to the generic character of the mya, the ani- 
mal is an asczdia, with the appendage ofa shell. Upon 
turning to the genus ascidia, we find it said, “ Corpus fix- 
um, teretiusculum, vaginans. Aperture. bine, ad summi- 
tatem ; altera humiliore.” To prove the impropriety of re- 
