a small cluster of roundish, yellow, irregular follicles, and frequently a smaller gland of two
or three follicles is placed a little in advance. They are connected by a long slender duct,
which opens into the mouth at the commencement of the oesophagus.
The oesophagus is short, with a longitudinally plicated mucous membrane, and is usually
bent into the form of an S, allowing the mouth to be advanced with great facility. The
stomach is a large pyriform pouch, which lies diagonally in the body (Figs. 1 c, 2 d, 3 d, 4 d), the
lower end approaching to the left side: it is continued in the form of a canal, in some species
wide and tapering, in others more constricted, down the median line of the back, and terminates
near the posterior extremity of the body in a blind sac. From the pouch and its
continuation, branches are given off in pairs, not quite symmetrical, but generally more or
less alternating. These branches, after being redivided in most of the species, give off smaller
tubes, which are continued into the branchial papillae. From the upper surface of the posterior
extremity of the stomach, where it is continued into the central canal, is given off a short
intestine, which passes to the right side, opening in a small nipple-like anus, generally
concealed among the branchiae. The inner walls of the stomach are longitudinally plicated
(fig. 13); the plications being usually continued more or less extensively through the branches.
The arrangement of the lateral branches in this curious digestive apparatus varies in different
sections of the genus, as given in the accompanying plates. In the first section, represented
by E. papittosa (fig. 2), the branches bifurcate once, or sometimes twice, before they reach
the extremities : in the second section, represented by E. coronata (fig. 4), the lateral branches
have a pectinated arrangement; the more simple forms of the third and fourth sections are
shown in E. olivacea (fig. 3), and E. despecta (PI. viii, fig. 8).’
The prolongations of the branches that enter into the papillae, there undergo a con-'
siderable enlargement and change of form, and from the variety and brilliancy of their
colouring, are the chief attraction of these elegant little animals. The simplest form of this
peculiar organ is met with in E. concinna, where it is a mere dilated tube, having its walls
slightly waved, and the inner surface sprinkled with darkish granules. In E. Farrani
(PI. 8, fig. 10) it still retains a considerable simplicity of structure, but becomes decidedly
sacculated. The complexity is much increased in E. olivacea, in which it is produced into
puckered follicles or sacculi. But in E. papillosa (fig. 9) it appears to attain its highest
development. The central canal is there somewhat tortuous, and gives off on all sides
variously-sized irregular blind sacs, which are crowded with little compound follicles. The
whole ofvthe inner surface is lined with a thickish layer of irregular vesicles or globules, filled
with numerous granules. These last, when submitted to a high magnifying power, are seen
to be of various sizes, transparent, rounded and nucleated. The whole of the internal
surface of the gland is covered with vibratile cilia. These compound glands are evidently
biliary organs, diffused throughout the several papillae, and supplying the place of a compact
liver, which is wanting in the body of these animals. The stomach and biliary organs are so
intimately connected in this genus, that it is not easy to point out the limits of each; they
appear to differ in different species. In E . papillosa the central canal is evidently a
continuation of the stomach, and the plicated internal membrane is not only continuous
throughout it, but also passes into the lateral branches, which thus appear to form a part of
the same organ. On the other hand, we find in some species coloured granules, similar to
those of the papillae, partially lining the ramifications, as in E . gracilis, E . rvfibranchialis,
E . Northumbrica, and others; while in E. despecta the central canal, all the ramifications,
and the glands of the papillae are coloured and granulated alike, implying a greater diffusion
of the biliary function.
The food, after being partially digested in the stomachal pouch, is driven in detached
portions through the alimentary system by the alternate contractions of the pouch and great
trunks leading from i t ; these contractions are only of a nature to produce an oscillatory
motion, which serves to promote that intimate mixture of the alimentary matters with the
hepatic and other secretions, necessary to the process of digestion.
A curious organ, apparently in connexion with the digestive system, but whose functions
are very imperfectly understood, is situated at the end of each papilla. It is a
small ovate vesicle, which communicates with the biliary gland by means of a slender canal
below, and at the opposite and narrower end opens externally through a minute aperture at
the extreme apex of the papilla. (PI. 8, figs. 9 a, 10 a, 11 a.) The walls of this vesicle, which
are seen of an opake white in the species with a transparent skin, consist of a strong thick
layer of finely interwoven circular muscular fibres. The contents appear to be arranged in
longitudinal masses. When very highly magnified these masses are found to contain long,
narrow, elliptical bodies, with faint double longitudinal markings, (fig. 14 a,) and globules of
various sizes, containing either one nucleus or several small granules in their interior. These
are imbedded in, and adhere to, a tenacious, obscurely granular mucus-like matter. We have
frequently seen the elliptical bodies violently ejected from the terminal orifice ; they are then
observed to be contained in little transparent membranous bags, each holding half a dozen
or more. (PI. 8, fig. 12.) In s6me species these bags likewise contain other and larger flattened
elliptical bodies, with a peculiar marking in the interior. (Figs. 13, 16.) Immediately
after expulsion the membranous bags burst, and the contained narrow elliptical bodies becoming
scattered, each shoots forth from the end first protruded, a much prolonged, slender, hair-like
filament. (Fig. 14.) On one occasion we observed an individual of E. picta, when moving
freely about, suddenly, and by a convulsive effort, eject from the points of the papillae a
minute stream of milk-white fluid, which curling upwards, mingled with the surrounding liquid
and was soon lost to view. The fluid exactly resembled the contents of the ovate vesicle when
forced out by pressure, and examined with a lens of low power. It appears probable that
this extraordinary apparatus at the end of each papilla is an organ of defence; and from the
resemblance of the minute bodies ejected to those stated to be thrown out by the Actinia, that
they are stinging bodies of a similar nature.
The vascular system appears to be as complete as in any of the order. The heart is
situated immediately below the skin, near the centre of the back, where it forms externally
an oval swelling; it is composed of two parts, a ventricle (PI. 8, fig. 1 a) and an auricle
(fig. Tft); these are inclosed in a very delicate pericardium of an elliptical form. The
ventricle lies in front of the auricle, and the communication between them is effected by
a small orifice on the under side. The ventricle is strong and muscular, and has in the
interior numerous fleshy anastomosing columns. When examined after death it is somewhat
pyriform, with the narrow end anterior, and having the aorta issuing from it.
This vessel (fig. 1 d) is of considerable size/and branches may be traced from it to most of
the principal organs. The auricle is much more delicate than the ventricle, and, like if, is
provided with fleshy-columns in the interior, only they are much finer and less numerous.