On the motion of Mr Alexander Bryson, seconded by Dr M'Bain, a cordial vote of thanks was unanimously given to Dr T. S. Wright for his valuable services as President of the Society, and for his learned and beautiful opening address.

Mr Bryson then called the attention of the Society to the value of recording facts, however trivial they might seem, and reminded the fellows that the discovery made by their distinguished member, Mr Peach, and communicated to this Society, of goniatites and other shells, near Durness, had induced Sir Roderick Murchison to remodel his strategraphical arrangement of the rocks of Scotland.

Dr M'Bain said that he was present when the first fossils from Durness were shown to the Royal Physical Society, and that the late Hugh Miller then considered them to belong to the Old Red Sandstone. At the same time, Mr Miller observed that other fossils, in a more perfect state of preservation, would probably be found in the same locality, that would enable geologists to decide what formation they belonged to. Dr M'Bain also remarked that simple facts might lead to important results in applied science as well as in the higher generalisations; and stated an instance within his own knowledge, to which the President had incidentally referred, of the application of Melloni's thermo-electric thermometer, by their distinguished member, Mr A. Bryson, to the detection of icebergs at sea, which might ultimately be the means of saving an incalculable amount of life and property.

Dr Wright then proceeded with a Report on the anatomy of the Hydroidæ.

by cannon—booming for a great and peaceful victory. A true and noble man hath laid aside his titles, and honours, and power; and hath passed from the uncertain and turbulent shadows of this world, to the serene light of the eternal day. Gentle, and wise, and good,-earnest in the work of the present, he was of those who, standing on the mountain tops, gaze wistfully on the brightening dawn of the future. Nobody," saith he, who, being dead yet solemnly speaketh—“ Nobody who has paid any attention to the peculiar features of our present era, will doubt for a moment, that we are living at a period of most wonderful transition, which tends rapidly to accomplish that great end to which, indeed, all history points-THE REALISATION OF THE UNITY OF MANKIND." (Speech of the Prince-Consort at the Lord Mayor's Banquet, 1850.)

The following Communications were then read :

I. On the Anatomy of Sacculina with a description of the Species. By JOHN ANDERSON, M.D. Plate XIII.

Three years ago I drew the attention of this Society to the fact of the frequent occurrence of Sacculina and Peltogaster on some of the Crustacea of the Firth of Forth. For some years past the subject of the affinities of these parasites has been occupying the minds of many foreign observers; and the following observations, therefore, are brought before the Society in the hope that they may tend to throw some light upon this difficult question. In the present paper I have purposely abstained, as far as possible, from dogmatising regarding their systematic position, but elsewhere I have referred them to the Cirripedes.* I may mention that the relative position of the investing sacs, the character of the ovaries and the ovigerous lamellæ, and the apparent hermaphrodite nature of the adult animal, when viewed in connection with the larval form, appear to me clearly to indicate their Cirripedial nature. Accordingly, in my graduation thesis, I created a new order (Sacculinacea) for their reception.†

"If

Among recent observers, Leuckart drew the attention of naturalists to Thompson's systematic description of Sacculina, and proposed the adoption of his generic term. we restore," he says, "the name Sacculina either for Peltogaster in Rathke's sense, or, at least, for the form characterised by Diesing as Pachybdella, we are only discharging an old, superannuated debt." In the same article he described a new form parasitic upon Hyas araneus, and which he named Sacculina inflata. In accordance with Leuckart's proposal, I use the term Sacculina as referring to the parasite alluded to by Cavolini, and as synonymous with

* Graduation thesis, "Contributions to Zoology."

+ The following are the characters of this order, as given in my thesis :-Cirripedia sine segmentis, oculis et appendiculis. Carapax sacciformis et appendiculata est: foramen in carapace situm est. Pedunculus annulo corneo affixus est. Os suctorium. Larva primo monocula cum 3 crurum paribus. Cirripedia parasitica sub abdomine Crustaceorum Decapodorum Brachyurorum.

Peltogaster carcini, Rathke, and Pachybdella Rathkei, Diesing.

The Larva. Pl. XIII. fig. 1.

The larva, in the first stage, is oval, and presents no marks of segmentation. Placed near the centre of the anterior margin of the body is a yellow speck-the eye (a). The ocellus is placed nearly in the centre of a dark-coloured ring (b). Krohn, who has observed a structure similar to this in the larva of a Balanide, regards it as the oesophageal ring. The lateral margins of the body, on either side of the ocellus, are prolonged into two horns (c); and in this respect the young resembles the Cirripedian larva in its first stage. It is provided with three pairs of natatory legs: the first pair (d) are situated immediately posterior to the horns of the carapace; they are uniramous, are provided at their extremities with bristles, and appear to be composed of two joints; the second and third pairs (d' d") are larger than the first, and are both biramous. The rami are furnished with bristles. The under surface of the body is prolonged into two spines (e e), which project beyond the posterior margin of the carapace. Besides these terminal spines, I have observed through the transparent body, two other structures (ff), which resemble very much the middle pair of spines described by Darwin as occurring on the larva of Chthamalus stellatus. The greater portion of the body is occupied by an oval mass of nearly spherical globules (g). The various transformations of the larva remain yet to be determined.

The Adult Animal. Pl. XIII, figs. 10, 11, 12, 15.

According to the present state of our knowledge, this parasite seems to be peculiar to the Decapod Crustacea. All the specimens I have obtained have been attached over the terminal portion of the intestinal canal (figs. 10 & 11 b′) of the crabs on which they were parasitic, the females of which they appear to infest more than the males. This latter circumstance seems to be owing to the large size of the purse of the female, as compared with that of the male crab, affording them a better protection and means of support.

The external sac (figs. 2, 4 a).—The external skin is a