remains imperforate as before, and is beyond the reach of surgical remedy. It may be added, that the subject of this history recognizes an increase of sexual feeling at and soon after the periods of enlargement of the ovary.

The second case was that of a young woman who had attained the age of twenty without having menstruated. She was a tall, strumouslooking person, in weak health. There had not been any wellmarked efforts at menstruation, but she had suffered slightly from lumbar pain. The mammæ were well developed. The pelvis was fairly formed. On examination I found the two ovaria just appearing beyond the external abdominal rings, and readily returning by pressure into their respective inguinal canals. They were of equal size and similar shape, being ovoid bodies about the size of small chestnuts. They were not tender when touched, although organically sensitive, and she had never experienced pain in them. The external sexual organs were somewhat less perfectly developed than usual; the vaginal orifice was closed, and no trace of a canal or uterus could be detected by exploration with a catheter in the bladder and the finger in the rectum. These organs, as in the former case, were absent. During the time I saw the patient, which was only for two months, the ovaria did not enlarge, although her general health improved.

II. "Further Observations on the Anatomy and Physiology of Nautilus." By JOHN D. MACDONALD, Esq., Assistant Surgeon R.N. Communicated by Captain DENHAM, R.N., F.R.S. Received January 13, 1857.

Both Professors Owen and Valenciennes noticed that the hollow subocular process of their specimens of Nautilus Pompilius was not tentaculiferous, and I may be permitted to say that this was also true of several examples of Nautilus Pompilius, and one of N. macromphalus, examined by me. But there is still another matter worthy of remark with reference to this process, namely, that its cavity may be traced downwards, inwards, and a little forwards, to within about the twentieth of an inch of the auditory capsule; indeed it would

appear as though provision had been made for the entrance of sonorous waves through a rudimentary external ear.

There can be little doubt that the eye itself is a modified tentacular sheath, so fashioned and endowed as to become the seat of the special sense of vision; but the subserviency of such a part to the faculty of hearing is much more obviously seen in the subocular process just noticed, which holds an intermediate position between the organ of vision and the tentaculiferous sheaths protecting the proper organs of touch.

In a figure which accompanies this communication, the auditory sac is exposed by an incision made in the groove between the funnellobe and the base of the tentacular sheaths. The subocular process is slit open to the bottom of its cavity, so as to show its termination in close proximity to the ear-sac. The interior of the tube is lined with a glandular membrane thrown into small folds, disposed longitudinally, but the exterior of the process is quite smooth like the rest of the integument.

I have often had some little difficulty in detecting the otolithes or otoconia, as the case may have been, in gasteropods long immersed in spirits or other preservative fluids; but in a specimen of N. Pompilius, kept for many months in strong gin, although the soft parts were far from being well preserved, I was enabled at the first attempt to remove the contents of the auditory sacs, and the minute elliptical otoconial particles, identical in character with those of N. macromphalus, were very distinctly seen under the microscope.

In a former paper, I first noticed my discovery of simple auditory capsules in, as I then supposed, the N. umbilicatus; but I find that I have incorrectly named my specimen, for on comparing the shell with the drawings of the several existing Nautili given in Sowerby's Thesaurus Conchyliorum,' it agreed exactly with the figure of N. macromphalus. I am indebted to my friend Mr. S. Stutchbury for the perusal of the work referred to, and my error is sufficiently accounted for by the scantiness of my own library.

With reference to the action of the great lateral muscles of Nautilus, the following ideas have suggested themselves to my mind.

As though preparatory to the complete separation of the body of the Cephalopod from the shell, which is usually present in the lower genera, the fasciculi composing the lateral muscles in Nautilus do not

perforate the mantle, and therefore cannot be directly fixed into the shell; they are, however, connected with it through the medium of thin filmy layers of a corneous texture, which frequently remain attached to the shell after the animal has been removed. The feeble hold of those muscles, even in a very recent state, is thus readily accounted for. Indeed, it is highly probable that the fixity of the body of Nautilus during the inhalation and forcible ejection of the respiratory currents is effected by the shell-muscles reacting upon one another, on the principle of a spring purchase, rather than by simple traction, as illustrated by the withdrawal of a gasteropod within its retreat, or the closure of the valves of a conchifer by the adductor muscles.

This view, which is supported by the foregoing facts, has its principal basis in the line of direction of the shell-muscles, and the angle at which they meet one another, at the root of the funnel-lobe; for the outer extremity of each being fixed, it follows that the first effect of the contraction of the muscular fibres would be to increase the angle just noticed; and this cannot possibly be accomplished, according to the recognized laws of muscular action, without tending to throw apart the points of origin, or in other words, exerting outward pressure against the internal wall of the shell, and thus, as it were, jamming the occupant tightly in its cell.

The action of the great lateral muscles of Nautilus here supposed, affords a remarkable contrast with the mode in which the posterior expanded arms of Argonauta embrace the exterior of its shell, particularly during the ejection of the expiratory current; while the withdrawal of the gasteropod into its abode, by the contraction of a veritable retractor, exhibits the exertion of muscular force in a very different direction.

In regard to the supposition that Nautilus macromphalus is the male of N. Pompilius, I may remark, that, besides my own specimen of the former, which proved to be a female, another, in very excellent condition, lately deposited in the Sydney Museum, is of the same

sex.

III. "Brief Description of a Ctenostomatous Polyzoon, allied to Vesicularia, occurring on the Australian Coast." By JOHN DENIS MACDONALD, Esq., Assistant Surgeon R.N. Communicated by Captain DENHAM, R.N., F.R.S. Received January 13, 1857.

In one of our visits to Moreton Bay, the sean was hauled at Moreton Island, and amongst the masses of sea-weed, &c. brought up with the net, I found numerous specimens of a very beautiful Polyzoon, a small portion of which I had previously dredged at Port Stevens from a depth of 5 or 6 fathoms.

The Polypidom may be said to have consisted mainly of rooted, spreading and plantlike portions, and short, straight creeping trunks, connected at both extremities with the fixed part of the former, so that the whole presented the appearance of an open lace-work, having all the transparency and lustre of glass.

The trunks and branches were nearly perfectly cylindrical, and composed of an outer membranous sheath distended with a clear fluid (which escaped with considerable force when the sheath was ruptured), and line-like reticulated vessels disposed in one plane, so as to communicate laterally with the polyp-cells, and divide the axis longitudinally into equal halves. The more central canals of this vascular plane combined to form a compound vessel, which opened into a spherical sinus with cellular parietes at the base of each branch.

The ramification of the Polypidom generally exhibited a trichotomous arrangement, with simple articulations occurring only where the branches were given off.

The cells were clustered in linear series on opposite sides of the branched axis, oval in shape, corneous in texture, with a terminal combed aperture, folding inwards by the contraction of four equidistant sets of muscular fibres, which imparted a quadrilateral figure to the opening.

The polypes were very minute, but exhibited distinctly all the important points of structure observable in those of Vesicularia and Bowerbankia, between which genera this polyzoon would appear to

lie. The ciliated tentacula, like those of Vesicularia, are eight in number, and do not possess the motionless hair-like processes which project from the back of each in Bowerbankia.

Although too much importance must not be attached to the actual number of tentacula surrounding the oral aperture, the tendency to multiply those organs must not be altogether forgotten. Thus, while there are but eight in Vesicularia, Bowerbankia densa and Bowerbankia repens possess respectively ten and twelve.

Both Bowerbankia and Vesicularia agree in the uniserial and unilateral distribution of the polypes, but in the present instance the cells are arranged in linear and bilateral clusters.

February 26, 1857.

The LORD WROTTESLEY, President, in the Chair.

The following communications were read :—

I. "Observations on the Natural Affinities and Classification of Gasteropoda." By JOHN DENIS MACDONALD, Assistant Surgeon R.N. Communicated by Captain DENHAM, R.N., F.R.S. Received January 13, 1857.

(Abstract.)

During his sojourn among the Feejee Islands, the author devoted much time to the anatomical investigation of recent Gasteropoda, with the view of discovering such indications of affinity in the details of structure as might serve as a basis for a natural arrangement of the order; and the present paper is designed to give a statement of some of the results of his researches, in order that the affinities of structure developed may be fairly examined and taken for what they are worth as principles of classification.

After pointing out objections to the foundation of primary divisions among the Gasteropoda on characters derived from the shell or from modifications of the respiratory organs, the author observes in respect of the value of sexual characters, that when the distinguishing features of a class are once satisfactorily determined, and this contains