and in Bendronotus there are several. In Lomanotus, Antiopa, and Proctonotus, the lateral
spines are numerous, the lingual membrane being broad in these genera, as in Boris. Lomanotus
has no central spines. Hepncea, Stiliger, and Alderia, also, present a peculiar modification
of this organ. In them there is a single longitudinal series of plates, as in Eolis; but they are
articulated, resembling the vertebrae of the spinal column, and each bears a very large, broad,
simple spine.
In addition to the dentigerous tongue, Boris repanda, B. pilosa, Goniodoris, Idalia, and
Ancday have a spiny, prehensile collar, placed at the entrance of the buccal organ, on what
has been denominated the buccal lip. B . coccinea, B. bilamellata, and Euplocamus croceus,
are also provided with a similar collar ; but in these the surface of the organ is roughened with
papillae or imbricated scales. The genera in which this apparatus is most strongly developed,
are characterised by narrowness of tongue and deficiency of jaws. It would therefore seem
probable, that the collar is a compensation for diminished prehensile power, consequent upon
these circumstances. At least it is rarely associated with a. powerful tongue, and never with
lateral jaws. There is a narrow belt of spines on the outer surface of the jaws of Tritonia} but
this would seem to differ from a prehensile collar. The tongue, in all the Nudibranchs, is more
of a prehensile than a rasping instrument: in Eolis the protruded jaws lay hold of its prey,
cutting out lump after lump, which the tongue, advancing, seizes by the aid of its recurved
spines, and with a backward motion carries to the entrance of the oesophagus. The broad
tongue of Boris acts at once in the capacity of both jaws and tongue^it is hollow or scoop-
formed, and, on being applied to the surface of its food is flattened out; the sides then collapse,
when the spines laying hold, a piece is torn or licked .out, as it were, and brought immediately
to the back of the mouth by the withdrawal of the tongue. The tongue in Tritonia must act
much in the same way, but here, probably from the different nature of its food, it requires the
assistance of a pair of powerful-jaws. In most of the species with a prehensile collar, the
lingual organ is narrow, has lost the scoop-like character, and is'functionally very similar to
that of Eolis. The collar, in these forms, will seize the prey somewhat in the manner of jaws;
then the tongue will be advanced, and do its work of carrying the food to the oesophagus.
The oesophagus, stomach, and intestine are well marked ; the former is generally short
and passes from the upper surface of the buccal mass. In the Borididce, and in a portion
of the Tritoniadce, there is a pair of well-developed salivary glands, pouring their secretion into
the buccal cavity, one on each side of the oesophagus. The Eolididce* appear to be devoid of
these organs, with the exception of Tethys, a very abnormal genus, in which they are quite
rudimentary.
The stomach varies considerably in size and form; and, in the Borididce, is frequently
buried in the liver. In them, too, there is occasionally, besides the buccal gizzard already
* We have described Doto as possessing salivary glands, in the account of that genus. A more
extended knowledge of the anatomy of these animals has, however, induced us to change our opinion
respecting the nature of these organs, which we are now disposed to look upon as glands for secreting
mucus to lubricate the foot, similar to those for the like purpose pointed out in Fiona. The salivary
glands of Calliopcea (Stiliger) described by M. Souleyet, will probably prove to be of the same nature.
The minute salivary glands described under the head Eolis, we are now satisfied do not exist. We
were deceived in our original examination by the lodgment of extraneous matter between the jaws and
the fleshy walls of the mouth.
noticed, an anterior stomach or crop, formed by a dilatation of the oesophagus. The most remarkable
modification of the gastric organ is found in Scyllcea, where it is armed with a belt
of horny plates or teeth. A similar armature of the stomach is not, as far as we are aware, to
be met with in any other Nudibranch.
The intestine is always short—in some of the Eolididce excessively so, never convoluted,
and, in the Borididce, terminates in an anal opening, on the medio-dorsal line, in the centre of
the branchial circle. In the Tritoniadce, and in many of the Eolididce, the vent is on the right
side. It is situated on the medio-dorsal line in Antiopa, Proctonotus, Alderia, Hermcea, and
Stiliger; in the three former, towards the posterior extremity, in the two latter, far forward in
front of the heart. In some others of the Eolididce it is latero-dorsal.
The liver presents two great types of form. In the Borididce and Tritoniadce it is entire
(excepting in Scyllcea, where it is broken up into six or seven globular masses), occupying its
normal abdominal position; in the Eolididce it is more or less diffused. In those genera with
an entire liver, it is very bulky, pouring the hepatic fluid into the stomach by one or several
large ducts. When, the gastric organ is free, as in B. tuberculala, it receives only one duct;
but in those species with the stomach buried in the liver, the bile enters through several large
openings in its under surface. In Scyllcea pelagica, and Boris tuberculata, the biliary secretion
enters at the cardiac extremity of the stomach: in Tritonia Hombergii, at the pyloric.
The diffusion of the liver is first seen in Tethys,* but in it the great bulk of the hepatic
organ is still found in the abdominal cavity; and the gastro-hepatic system is only in a rudimentary
state, though developed distinctly on the plan of that of Eolis. Lateral vessels are
given off from the stomach and liver, which pass to, and seem to penetrate, the papillae on the
sides of the back between the branchial tufts. In the greater number of the Eolididce, however,
the liver has entirely disappeared from the abdomen, and is broken up into numerous minute
portions or glands which are thrust into the branchial papillae. The delicate ducts from these
glands pass inwards and unite to form great hepatic ducts or trunk channels, which open into
the stomach. In the ProctonoUnce, Glaiicince, and Eolidince, there are three such trunk-channels,
two lateral and anterior,—one central and posterior: in the last-named sub-family the
posterior duct lies above the ovary; in the two others, below it, shewing, in this respect, their
relationship to the Borididce and Tritoniadce, in both of which the ovary overlies the liver.
The Hermceince have four great gastro-hepatic ducts, all of which are lateral,—'two being anterior
and two posterior. The great ducts, and the numerous branches leading to them from the
glands of the papillae, form the gastro-vascular system of M. Milne Edwards, and M. de
Q,uatrefages.
The gland of each papilla has appended to its extremity an ovate vesicle, which communicates
externally by a minute -orifice at the apex of the respiratory organ. This vesicle,
which has been observed only in Eolis, has the power of discharging filamentous urticating
bodies.
* In the account of Scyllcea, under the head of the genus, we have described a series of vessels
or tubes passing from the hepatic globular masses to the skin and branchial tufts j these we deemed at
the time to represent, in a rudimentary form, the gastro-hepatic system of the Eolididce, but we are
now inclined to consider them as veins, carrying blood from the biliary organ to the aerating surface,
and therefore of the same nature as the hepatic veins in Tritonia, and as the great hepatic trunk vein
in Doris.