In the Dorididce there is generally a small pancreatic organ—a glandular sac—opening
into the intestine at its*) unction with the stomach. In D. tuberculata, this organ is situated at
the cardiac extremity of the gastric pouch. There is also a rudimentary pancreas in Tetliys.
Reproductive Organs. All the Nudibranchs are hermaphrodites, each individual being
furnished with male, female, and. androgynous parts. These organs, taken together, are very
bulky, and occupy the greater portion of the abdominal cavity. They communicate with a
common vestibule, opening upon a nipple-like process on the right side of the body, and always
below the mantle, when it is present.
The male intromittent organ is exserted in front; behind it opens the vulva, and a little
above and between these two orifices is the vaginal opening, leading to the androgynous
apparatus. The penis is usually long, tapering, pointed and perforated, and the testis is
composed of a convoluted glandular tube, more or less voluminous, which, in some of the
Dorididce, is rolled up into a dense mass, forming a compact gland-like organ. One end of
this tube is connected with the intromittent organ, the other with the oviduct.*
The ovary is of considerable magnitude, and occupies the posterior portion of the
abdomen. In the Dorididce and Tritoniadce, it is spread over the upper surface of the liver;
in the Eolididse, it is a bulky, lobulated organ, filling up the space held by the liver in the
other members of the order. The oviduct, as it leaves the ovary, is very slender; it soon
widens and is more or less convoluted, and, after joining the testis, and receiving a duct from
the androgynous apparatus, sinks into a large mucus-gland, composed of a convoluted tube,
that opens into the vulva. This gland secretes the mucus, which, on reaching the surrounding
water, is transformed into the transparent gelatinous substance in which the eggs of the
Nudibranchs are always imbedded.
The androgynous apparatus consists of the vagina, or copulatory channel, which unites
with the oviduct, and has seated upon it one or two spermathecse: in the Dorididce always
two; in the Tritoniadce and Eolididce generally only olie. The connexion of the androgynous
with the female parts is somewhat modified in Tritonia and Tetliys.
Such is the predominant arrangement of these organs. There are, however, occasional
modifications. Thus, in Doris Johnstoni, and Doris tomentosa (of Verany) the male organs
have added to them a stiletto, which lies within a sac in front of the penis : this sac can be
everted, and when so, the stiletto projects from the apex of a long penis-like organ. This,
like the dart of Helix, is- probably for a stimulating purpose during, or previously to, coitus.
But the Hermceince present the most important deviations. In this sub-family the male and
female orifices are divided from that of the androgynous apparatus. The two former openings
are placed close together at the base of the right tentacle, and when these parts are fully
retracted, only one opening is visible externally. The copulatory orifice is removed to some
* Having completed our investigation of the anatomy of the various genera, we think it only
right to state that several facts have been observed, particularly in the anatomy of the Polycerinee,
which would seem to favour Her Heinrich Meckel's views as to the compound nature of the ovary of
these animals. When in season, it is distinctly composed of two parts, one containing ova, the other
• spermatozoa, and these latter have been found lying in parallel order, and apparently in an incipient
.state. The oviduct is, however, simple, and does not hold within it a vas deferens, as supposed by the
same high authority. Therefore, if the so-named ovary he really composed of ovary and testis, the
oviduct must be equally oviduct and vas deferens.
little distance backwards. The testis is composed of two much-branched tubes, which lie one
on each side of the body, and extend almost from the head to the tail. The ovary is formed of
a number of distinct, globular, ovigerous sacs, which are united by systems of minute tubes to
a large central oviduct. This duct, on its way to the vulva, communicates, as usual, with the
testis, spermatheca, and mucus-gland. The apex of the intromittent organ in Alderia carries
a crystalline spur.
Organs of Circulation and Respiration. These consist'of central organs of propulsion,—a
systemic and portal heart,—arteries, veins, and sinuses or lacunes; and of laminated, branched,
or papillose branchiae, arranged either on the median line, or along the sides of the back.
The systemic heart lies always immediately below the skin of the back, and consists of
two chambers,—an auricle and a ventricle,—enclosed within a pericardium. A large aorta
passes forwards,distributing branches to the various organs; and the blood is returned again
to the heart in a partially aerated state, only a portion of it having passed through the
branchiae. The blood system is somewhat modified in each of the three- families of the order.
In the Dorididce, the systemic circulation is twofold, general and partial. By the former, the
larger quantity of the blood, after supplying numerous- organs, reaches a general system of-
sinuses or inter-visceral spaces; then passes into the sinuses or cellular tissue of the skin, and
is returned to the auricle by two lateral veins. By the latter, that blood only which goes to
the liver-mass, comprising liver, ovary, and kidney, enters the special respiratory organ by a
great hepatic or afferent branchial vein, and, after circulating therein, arrives at the auricle
from behind by a single, median, efferent or branchio-cardiac vein.
The partial or hepatic circulation is probably provided with a complete system of capillaries,
and has, in connexion with it, a portal circulation, to which is appended a ventricle or portal
heart, that lies under the pericardium, the latter being related to the former as an auricle.
This portal heart propels venous blood into the renal and hepatic organs.
In the Tritoniadce, the systemic circulation is likewise divided into two portions; but in
th is. family, taking Tritonia as the type, there are six afferent branchial, or hepatic veins;
three passing from each side of the liver mass to the branchiae. The blood is returned to
the auricle by two lateral venous trunks, or efferent branchial veins, whjch, however, do not
convey merely aerated blood from the gills, but also drain the blood-sinuses of the skin; they
therefore carry to the heart a partially aerated or mixed stream, and are not to be looked upon
as the anatomical equivalent of the efferent branchio-cardiac vein of the Dorididce, but rather,
as the homologue of the two lateral veins, bringing the blood from the skin to the auricle.
The hepatic circulation of the Tritoniadce is undoubtedly as complete as that of the Dorididce,
and is also provided with a portal heart.
The systemic circulation in the Eolididce is simple, there being apparently no partial or
hepatic circulation. All the blood sent to the various organs passes into the great abdominal
sinuses, or inter-visceral spaces, and then enters the cellular tissue of the skin, a portion of it
penetrating the branchial papillae, and in this way it is returned to the heart by a system of
efferent branchial veins, which combine to form three great trunks, two being lateral, and one
posterior; these bearing the blood from the gills, also receive it from the sinuses, or cellular
tissue of the skin, and consequently pour into the auricle a partially aerated, stream, as in the
Tritoniadce. The Eolididce are likewise provided with a portal heart, which may probably
supply venous blood to the glands of the papillae.