after extrusion, fully half an inch long, and have almost parted with the nutritive portion of the vitellus. There are many, however, that have made less progress, and have still a large yelk-mass attached to the upper part of the thorax immediately behind the pectoral fins. On the third day after exclusion from the ova, the mouth and jaws were quite distinct, the pectoral fins had appeared, and the outlines of the branchial arches were plainly visible. The cardiac contractile sac, which was seen in the embryo, was now found to contract and dilate sychronously with a fluid movement along the ventral aspect, which could be traced backwards four-fifths the length of the fish, where a notch in the delicate fin membrane appeared to indicate the separation between the abdominal and caudal portions of the animal. The progress of development has been watched daily, and will be more fully detailed when the observations are completed.

As it is uncertain whether the young fry will exist long enough to pass into their adult condition, I have thought it proper to give this brief notice to the Royal Physical Society, and at the same time to exhibit living specimens, along with pencil drawings illustrating the various phases of development from the first rotation of the embryo seen in the ovum until the present time.

Dr T. S. Wright mentioned that he had noticed a similar development, but was doubtful if the ova were herring spawn.

III. (1.) On the Difference between the young Herring, Clupea harengus, and the Sprat, Clupea sprattus. (2.) On the Food of Fishes. By J. M. MITCHELL, Esq.

Mr Mitchell described the various differences between these distinct fishes; and proceeded to detail the results of the examination of the contents of the stomach in various genera and species of fishes.

IV. On Phryxus Paguri. By JOHN ANDERSON, M.D. In the month of May last year, when dredging in the Firth of Forth, I had the good fortune to meet with this in

teresting, and, according to its discoverer, Rathke, "recht selten parasit." As it is a new and interesting addition to the fauna of the Scottish seas, I shall shortly describe its external characters. This remarkable Bopyridian is fixed with its dorsal surface to P. Bernh., and from its anomalous position, one is apt to confound the ventral with the dorsal surface of the body. By means of its seven prehensile feet it adheres with considerable tenacity to the soft abdomen of the crab. In Phryxus, as in the other Bopyridæ, the proportions of the female greatly exceed those of the male individual, which is always found associated with, and leading a parasitic life upon, the former. Differing in size, they also differ in external form.

The female always selects the left side of the crab as its habitus, which, I suppose, is owing to this side of the crab being always in relation to the widest part of its appropriated dwelling. It is about half an inch in length and a quarter of an inch in breadth; all my specimens were of a pure white colour. The body of the animal, with the exception of the caudal appendage, is nearly of the same breadth throughout its whole extent; its anterior margin is rounded. As already stated, the dorsal surface is applied to the abdomen of the crab, and is flat, but slightly concave in the centre, and is divided into seven segments, each segment bearing a pair of prehensile feet. The ventral or uppermost surface is in relation to the shell in which the crab lives, and, like the dorsal, is distinctly segmented, but is hidden from view by six leaf-like membranes, which form the breeding cavity for the ova.

The head of the animal cannot be detected on the ventral surface until the bladder-like pouches which overlap it are removed. This portion of the head consists of a large under lip, behind and over which are placed two valve-like bodies; these bodies, in reality, are the altered pouches of the head segment. When viewed from the dorsal aspect, the head has a quadrangular appearance, bearing upon the centre of its anterior margin a small rounded process. The first pair of antennæ are small, and consist each of three joints, the terminal joint bearing a few bristles. The second pair are

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much larger than the first; they consist each of four joints, the two terminal joints being provided with a few bristles. Eyes are wanting in the female.

The segments of the dorsal surface of the body are symmetrical, with the exception of the sixth, the unsymmetrical character of which is due to the animal being slightly curved, the convexity of the curve being towards the right side, and involving this segment. The segments gradually increase in size from the third to the sixth; the latter is very much expanded on the right side of the mesial line, corresponding to the convexity of the curve of the body. The seventh segment is symmetrical, but very much smaller than the preceding one. All these segments bear feet, which are very much distorted. From the different relative proportions of the segments, the feet are placed at various distances from each other. The first pair closely surround the head, and have the second pair intimately applied to their external margins. The third pair are placed very near the second, but slightly posterior to them; and the fourth pair are removed at some distance from the former, and also from the fifth pair, which lie behind them. A considerable interval exists between the fifth and sixth pair of feet, which is especially marked upon the right side of the animal. The sixth and seventh pair lie contiguous to one another.

Projecting beyond the posterior margin of the body (seventh segment) are the five branchial segments, all of which, with the exception of the terminal one, carry a pair of oval pedunculated branchiæ. The segments are rounded, and diminish in size as they approach the extremity. The terminal one ends in an oval-shaped process, which probably performs the same function as the branchiæ.

The six ventral membranes of the breeding cavity increase in size as they approach the posterior extremity. The first or head pair differ in their form from the other five, from which they are also distinguished by their edges not being overlapped.

They appear to be supported upon very short jointed stalks, and they consist of two portions, an anterior and posterior. The anterior portion is oblong in form, and bears

upon its ventral surface four rounded tubercles, and has a curious crescent-shaped pedunculated appendage attached to the posterior extremity of its external margin; the posterior portion is about half the size of the anterior, and is convex externally, and slightly concave on its internal margin.

The connections of the remaining five pouch-like membranes are as follows:

The second membrane covers the valve-like leaf of the head and is overlapped by the third, which is partially covered by the fourth; this, again, overlaps the anterior extremity of the fifth, the remainder of which, and the posterior half of the fourth, are hidden from view by the largely developed pouch of the fifth, sixth, and seventh segments. By this arrangement the plates visible from the belly side are the third, fourth, and sixth. The sixth plate is minutely serrated along its margins. In one of the specimens I examined, the fourth, fifth, and sixth membranes were filled with ova.

The pale-yellow coloured male is a very little more than one line in length, and consists in all of nine segments, which diminish in size as they approach the caudal extremity. The anterior segment (head) is symmetrical, and bears two eyes. Projecting beyond its lateral margins are the external antennæ, which consist of four joints. Placed internal to these, and completely concealed by the head, are the internal ones, which only consist of three joints. Each of the remaining segments, with the exception of the terminal one, carries a pair of feet which are provided with sharp claws. The segments are rounded at their external margins.

V. Observations on British Zoophytes and Protozoa. 1. Clava nodosa. 2. Acharadria larynx. 3. Zooteirea religata. 4. Freya (Lagotia) obstetrica, Freya stylifer. 5. Chatospira maritima. 6. Oxytricha longicaudata. By T. STRETHILL WRIGHT, M.D. (Plate XVII.)

1. Clava nodosa (n. sp., T. S. W.)

Polypary creeping. Scleroderm membranous, 'Polyps single, small, aurora-coloured, each springing from a small knot of convoluted tubes.' This zoophyte was found on the fronds of Delesseria sanguinea at Queensferry and Largo."

The very delicate threads of the polypary creep over the fronds of the seaweed, and at intervals twine themselves into a convoluted knot of membranous tubes, from which a single polyp arises. The species occurs only at low tide mark; while C. repens, for which it may be mistaken, is found in shallow rock pools.

2. Acharadria larynx. (Pl. XVII. figs. 7, 8.)

Polypary branched, spirally twisted. Polyps pale orange, with two rows of tentacles. The lower row from 4 to 12, the upper row from 2 to 8 capitate."

On stones carrying Caryophyllia Smithii, received from Ilfracombe. This little Tubularian was about a quarter of an inch high, with three polyps, and resembled in habit Tubularia larynx. It bears the same relation to Vorticlava that Corymorpha does to Tubularia larynx.

3. Zooteirea religata.

I described this animal to the Society about three years ago. It is a stalked Actinophrys. The body, as in other animals of this class, consists of two elemental tissues, to which I have given the term ectosarc and endosarc, -terms which have been adopted by Dr Carpenter. The ectosarc or external tissue is prolonged into a thick brush of the most delicate contractile palpocils or tentacles, like threads of spun glass (Pl. XVIII.), by which the animal is constantly seizing small organic particles, and conveying them to the endosarc or inner tissue, which is the nutritive element. I stated that the stalk was formed of a prolongation of the ectoderm, similar to the tentacles; but, having again discovered large colonies of these animals last summer, and again this winter, I have been enabled to study the structure of the stalk more closely, and find that