362 
MOLLUSCA. 
Mollusca. oyarium is situate in the posterior part of the abdomen. The 
~~” oviduct is tortuous in its course, passes along the surface of 
the testicle, and, after uniting with a clavate appendage, 
opens into acommon canal. ‘The testicle is firm, apparently 
homogeneous in its texture, of a yellow colour, with spiral 
ridges on its surface. The vas deferens arises from a com- 
plex, glandular body, and unites with the common canal. 
This common.-duct, before it reaches the external orifice, 
receives the contents of the pedunculated vesicle, and has 
attached to it a botryoidal, glandular organ, the use of which 
is unknown, but which some suppose to be employed to se- 
crete an acrid liquor regarded as venomous. It is obvious 
from this structure, that the seminal fluid and eggs must 
come in contact in the common canal, and at the single ori- 
fice, provided they are both ejected at the same time. From 
the orifice to the right fore-feeler there is a sulcus, leading 
to the pore containing the retractile penis. This organ, 
like those of the other mollusca, is solid. It terminates in 
a small filament. The external groove is the only connec- 
tion between it and the other sexual organs. 
There is a peculiar secretion of a purple fluid which here 
deserves to be recorded. It issues from a spongy texture, 
underneath the free side of the dorsal plate. Connected 
with this cellular reservoir is a glandular body of a consider- 
able size, which is supposed to secrete the coloured fluid. 
This gland is supplied by a large branch of the glandular 
aorta, and gives out two very large veins to the left vena 
cava. The fluid itself has never been carefully investigated. 
It is not altered by the air after drying, nor is its colour de- 
stroyed by acids or alkalies, although the tint is a little 
changed, and rendered less pure. Both these reagents pre- 
cipitate white flakes from the fluid. This liquor is poured 
out by the animal when in danger or constrained, and co- 
lours the water for several yards around. It ejects it readily 
when put in fresh water; and when entangled in a net, se- 
veral yards of it in the neighbourhood are sometimes stain- 
ed, greatly to the amazement of the unsuspecting fishermen. 
The Aplysia has been long known in the records of su- 
perstition under the name of the Sea Hare. Its flesh, and 
the inky fluid it pours out, have been regarded as delete- 
rious to the human frame. Even to touch it was supposed 
to occasion the loss of the hair ; while the sight of it would 
not fail to subdue the obstinacy of concealed pregnancy. 
The progress of science has exposed the errors, or perhaps 
tricks, of the earlier observers, and proved the innocence of 
an animal formerly invested with every repulsive and noxi- 
ous attribute. The A. depilans, the type of the genus, is 
of frequent occurrence on the British shores. The A.punce- 
tata of Cuvier may be regarded merely as a variety. 
Genus DoraseLta.—Dorsal plate a solid shell. 
This genus differs from Aplysia, in the dorsal plate being 
calcareous and hard. The fore part of the body is narrow ; 
behind it is larger, and obliquely truncated. The disc thus 
formed is circular, surrounded with a fringe of fleshy fila- 
ments. From the centre of this disc, a longitudinal slit ex- 
tends forward, a little way beyond the anterior margin, and 
contains the branchize. The position and structure of the 
other organs are precisely similar to those of the Aplysia. 
This genus was instituted by Lamark, from characters de- 
rived exclusively from the dorsal plate or shell. Cuvier 
afterwards examined a species brought from the Mauritius 
by Peron, which he considers as the one figured by Rum- 
phius in his Amboinshe Rariteithamer, tab. x. No. 6, and 
which he has consecrated to his memory, naming it Dola- 
bella Rumphii. 
Genus Prevroprancuvs.—Tentacula two in num- 
ber. Cloak and foot expanded, between which, on the 
middle of the right side, the branchiz are placed. The cloak 
is strengthened in the middle, above the branchiz, by a thin 
expanded subspiral shell. The neck is short, and in some 
contracted, with the front emarginate, exhibiting the com- 
mencement of the inferior tentacula. 
are tubular and cloven. 
dorsal plate. In front of these are the orifices of the organs 
of generation, and the anus is situate immediately behind 
the gills. The mouth is furnished with a short retractile 
proboscis. The tongue occupies both sides of the mouth, 
and is covered with spines. The gullet is enlarged into a 
kind of crop before it enters the stomach; this is folded, and 
is divided by contractions into three parts. The first sto- 
mach has muscular walls of moderate thickness, with a single 
longitudinal band. The second has membranaceous walls, 
with longitudinal internal ridges, and the third has thin and 
simple walls. The gut is short. The salivary glands are 
situate at the folds of the stomach, and by two canals empty 
their contents into the mouth. The liver is placed on the 
stomach, and empties itself into the lower part of the crop. 
The heart is nearly in the middle of the back. Its auricle 
is on the right side, at the base of the branchiz; and the 
ventricle sends out at the opposite side three arteries. 
M. Cuvier has figured and described the P. Peronii with 
its anatomical details. Two species likewise appear to be 
known as natives of the British seas. 
Genus Buiia.—tThe head is destitute of tentacula and 
the body of the animal, protected by a convoluted shell, is 
oblong, becoming a little narrower in front. Below, the foot 
is broad, thin, and waved on the margin, expanded on each 
side behind, and capable of being turned upwards. At the 
posterior part of the foot, but separated from it by a groove, 
there is a broad, membranaceous appendage, a part of which 
is folded upwards, and a part spread over bodies, like the 
foot. It assists in closing the mouth of the shell, and in its 
position and use is analogous to the operculum, in the fol- 
lowing order. Above the foot, in front, also, but separated 
from it by a groove, there is a fat, fleshy expansion, which 
Cuvier terms the tentacular disc, considering it as formed 
by the union of the inferior and superior tentacula. In the 
centre of the disc, in the Bulla hydatis, (Lin. Trans., vol. 
ix. tab. 6, f.4), Montagu observed two eyes. Between this 
portion of the back and the posterior extremity, is the dorsal 
plate or shell, forming the genus Bulla of conchologists. In 
some species, this shell is covered by the integuments, while 
in others it is exposed. But in all, the part containing it is 
partially concealed by the animal, by means of the reflected 
margins of the foot, and its appendage. Along the right 
side of the body there is a groove, formed by the foot and 
its appendage, on one side, and the dorsal plate and tenta- 
cular disc on the other. The branchiz are situate ina 
cavity under the shell or dorsal plate, and resemble those of 
the Aplysia. Behind the gills, in the lateral groove, is the 
anus ; and in front of these, the orifice of the united organs 
of generation. The penis isremovedas in the Aplysta, and 
connected by a similar slit. 
The mouth is, as usual, in front, above the foot and be- 
neath the tentacular disc, both of which serve as lips. The 
cheeks are strengthened on each side by a corneous plate. 
The tongue is well developed in some, as the B. ampulla, 
while in the B. aperta it is reduced to a small tubercle. 
The gullet is large, and in the B. ignaria makes two folds 
before entering the gizzard. This last organ is fortified by 
three testaceous plates, convex and rough on the inner sur- 
face, and attached to strong, muscular walls. These plates 
exhibit in the different species considerable varieties of form 
and markings. The intestine, before terminating in the 
anus, makes several convolutions in the substance of the 
liver. The salivary glands exhibit considerable differences. 
In the B. ampulla they are long and narrow, and their in- 
ferior extremity fixed to the gizzard. In the B. aperta and 
lignaria, they are short, with the extremity free. In the 
B. hydatis they are long, unequal, and the extremity of the 
one, belonging to the left side, is forked. The liver forms 
a part of the contents inclosed in the spire of the shell. It 
The upper tentacula Mollusea. 
The gills occur at the edge of the —=\—=" 
