(such as the liver and the cells of Leydig scattered throughout the conjunctive tissue)
co-operate in the ■work of excretion.
T he R epboduotiVe System.
Topographically this system falls into two parts : (1) The hermaphrodite gland, which
is spread as a layer over the liver and not recognizable as a separate organ on superficial
examination. (2) All the other organs, which, being collected in the right anterior portion
of the body, are often spoken of collectively as the anterior genital mass. Though not
organically fused they are mechanically pressed together and connected by membranes,
so that being themselves largely composed of thin tubes and vesicles flattened against
the large glands which secrete th$ coverings of the ovum, they are extremely hard to
disentangle.1
The hermaphrodite gland is of a yellowish colour; it lies among and to some extent
below the ramifications of the kidney, but also covers the lower surface of the liver as
well as the sides of the cleft in which the stomach is placed. Its appearance differs
according to its full or empty condition, but when it is distended with ripe products it
appears to form a continuous coat spread over the whole liver-surface. I t is really composed
of numerous lobes, subdivided again and again. The ultimate lobes consist of a
central portion containing spermatozoa, round and above, which are smaller globular
ovarian follicles, opening into the central portion. All the lobes are connected by a
system of fine canals which gradually unite so as to form larger and larger tubes, until at
the right anterior end of the liver the two principal tubes may be seen to join in the
hermaphrodite duct which passes over to the anterior genital mass.
The size and outline of this mass depend chiefly on the mucus and albumen glands,-
which are greatly distended in the breeding season.2 I t is more convenient to examine
them before this dilatation begins. They are then found to form a roughly oval pad or
layer (say 25 mm. long with a maximum thickness of 7 mm. in a specimen of moderate
size) pressed against the right anterior body-wall and thinner behind, where it is slightly
hollowed in order to accommodate its shape to the liver. The hermaphrodite duct
forms a bridge between the two organs (see Text-figure 6), and passes straight from the
liver to the inside of the anterior end of the genital mass. There it dilates at once
1 Though Alder and Hancock described the various reproductive organs with accuracy they
seem to have misunderstood their functions and relations. They say quite correctly that the whole
apparatus consists of three parts: (1) male, (2) female, (3) « androgynous.” ^ But they apparently
supposed that these three parts were represented respectively by—(1) the vas deferens; (2) the mucus
gland with its annexes, and the hermaphrodite gland which they term ovary; .(3) the branch bearing
the two spermatothecas. But all naturalists who have studied the group are now agreed that the
posterior gland is not a mere ovary, but hermaphrodite, inasmuch as it produces both ova and
spermatozoa, which are dealt with separately by the organs of the anterior genital mass. After the
hermaphrodite tube has bifurcated, the remaining organs are considered as exclusively male or
exclusively female. But if self-fertilization (which is certainly not the rule) were proved to occur even
occasionally, the branch bearing the spermatothecas might be described as androgynous.
3 I t should be also mentioned that if they are put under water for dissection they are liable to
become enormously dilated.
ANATOMY. 47
into a thickish tube (say 2 mm. broad) disposed in a few closely fitting coils and known
as the ampulla (d). I t then bifurcates and sends one branch (female) into the albumen
gland (l). The other branch (ƒ) is the elaborately twisted vas deferens, whose convolutions
are piled on the top of the ampulla and hide the point where the bifurcation takes
place. They then run over the outer wall of the gland, until the tube, which has been
growing gradually narrower, enters the pointed end of a conical bag (g). This is the
intromittent organ. In the state described (which is that usually found in preserved
specimens) it bears a small prominence, the glans, at the bottom of the bag, and it may be
compared to the finger of a glove pulled outside in. But on occasion it can be evaginated
so that the glans forms its external tip and the vas deferens traverses the whole length of
the finger.
The male genitalia of the Dorids are seen in their simplest form in D. kiberculata, but
in allied genera exhibit many complications :? (1) The upper part of the vas deferens may
bear a gland of considerable size known as the prostate. (2) There may be accessory
glands near the termination of the vas deferens. (3) The vas deferens in its lower part,
or the glans, or both, may be armed with spines, or the glans may be armed with 'a single
stylet. (4) The glans is often considerably larger and may assume various shapes.
Whereas in many hermaphrodite Mollusca the female part of the genital system
consists of a single passage (with annexes) which serves both to receive spermatozoa and
to expel eggs, in the Dorididge it is divided into two passages, each with annexes, one to
conduct the spermatozoa from the copulatory orifice to the unfertilized ova, and the other
to expel the fertilized ova after investing them with various envelopes which ultimately
assume the form of a nidamental ribbon. Starting from the external opening the first
passage commences as a broad tube (i), which contracts and passes into the spermato-
theca (_ƒ), a. thin-walled vesicle of considerable dimensions, globular in shape if distended,
but frequently somewhat flattened. Close to the point where the duct from the exterior
enters the spermatotheca another duct leaves it1 and proceeds towards the oviduct, a
name which may be applied to the other branch of the female genitalia, extending from
the point where the hermaphrodite ampulla bifurcates into male and female portions (e)
to the external orifice of the mucus gland.2 The tube which runs from the spermatotheca
to the oviduct bears on its course a second vesicle (7c), here called the spermatocyst,3 considerably
smaller than the spermatotheca and with thicker walls. I t is elongate and
somewhat bent: it does not communicate with two ducts like the spermatotheca, but is
connected with the main tube by a single short duct and hence looks like a pear on its
stalk. After receiving this duct the main tube enters the mucus-albumen gland complex
~ 1 In some Dorids (but not in D. tuberculata) this second duct obviously starts from the wall of
the first.
3 The short stretch between the point where the vas deferens branches off and the point where
the duct of the spermatocyst enters is not functionally a common channel which bifurcates into two
parts (as is the hermaphrodite duct), but it is the path which the ova traverse on their way to be
fertilized and ultimately laid. Hence from beginning to end it is an oviduct.
3 The nomenclature spermatotheca and spermatocyst, used by Bergh, seems to me convenient, for
it distinguishes the two .organs without committing us to any theory as tq their functions. But other
authors call the spermatotheca bursa copulatrix or copulatory pouch, and others again call both organs
receptacula seminis or seminal bladders.