Ardsheal Hill is situated in Argyllshire amidst country of great petrographic interest. It is easily reached by road or rail, for it overlooks the main road from Oban to Port William, and is under 2 miles from the station of Kentallen on the Ballachulish Branch of the L.M.S. Railway. The area considered in the present communication is bounded by Loch Linnhe on the west and on the east by the above-mentioned road.

During the course of experiments on the toxic effects of tetrachlorethane on minnows, Phoxinus phoxinus (L.), Mr J. Wilson Dougal, B.SC., found “cellular bodies” in a portion of the brain tissue of a dead minnow which he had spread on a microscopic slide. Sections of the head of the minnow were subsequently made by Mr Richard Muir and submitted to me for an opinion on the nature of the bodies. Examination showed that they were immature Trematodes of the family Holostomidæ. I handed the sections and a living minnow, sent at the same time (May 1923), to Miss Bannerman for further study, remarking that the only Trematode hitherto recorded as occurring in the brain of fresh-water fish in Britain was a Tetracotyle in the brain of the lamprey and the ammocœte. I subsequently directed her attention to Mataré's account (1910) of a similar worm which had been found in the brain of minnows collected in Switzerland and in Germany. Miss Bannerman studied numerous examples of the parasite during June and July 1923 and in September 1925, but she had to leave in October 1925, before the work could be completed, to take up a post in India. The comparison with previously recorded species of Tetracotyle, the discussion on the morphology of the ventral sucker, the account of the excretory canals, and a number of details in other parts have been added since she left.—J. H. A.

The characters of the sporangium have been widely used in the phyletic treatment of Ferns, and one of the most important features has proved to be the nature and position of the annulus. As Professor Bower has pointed out, the position of the annulus has long been regarded as an important character in the systematic treatment of Ferns. In the more advanced groups the annulus forms a very precise dehiscence mechanism consisting of a single layer of indurated cells passing round the sporangium in different positions in the various groups. With very few exceptions, notably found in the Gymnogrammoid circle of affinity, the structure and position of the annulus is constant in any one species. In the more primitive groups of Ferns, however, the dehiscence mechanism is much less precise, and a re-examination of the sporangia of the Osmundaceæ has shown that these are by no means constant in structure and that, in particular, they show considerable variation in the characters of their annulus. These latter variations have proved to be of interest in relation to two questions:

1. The systematic placing of certain fossil sporangia.

2. The evolution of the more definite annulus of the higher Leptosporangiate Ferns.

Other points of interest emerged, such as the occurrence of abortive sporangia in this group, and certain facts relating to the position of the sporangia with relation to the margin of the frond.

A description of the sporangia of a number of species of Osmunda and Todea will first be given. The bearing of these facts on the problems above mentioned will then be discussed.

Among the commonest and most abundant plant-remains in the Carmyllie and Cairnconon Beds of the Caledonian Lower Old Red Sandstone are branched linear axes about 2 mm. in width. These often occur in a fragmentary condition, but more connected portions demonstrating the morphology of the plant are also found. Though often associated with Parka and Nematophyton, the plant known as Zosterophyllum myretonianum is usually readily recognisable by its definite outline and uniform diameter, by its modes of branching, and by the remains of structure which it sometimes retains. As will be seen below, the axis of this plant was traversed by a single median strand that was composed of tracheides. Zosterophyllum is thus of special interest as the most ancient vascular plant known from British rocks. Some other plant-remains that may be confused with it have also been met with, though less commonly. These will be briefly considered, not merely for this reason, but on account of the very different and peculiar type of structure they exhibit.

The Vittarieæ, as described by Christensen, comprises five genera, viz. Vittaria, Monogramma, Antrophyum, Hecistopteris, and Anetium, all of which are epiphytic forms growing in the damp forests of the Old and New World Tropics. All of them possess creeping rhizomes on which the fronds are arranged more or less definitely in two rows on the dorsal surface. The fronds are simple in outline, with the exception of those of Hecistopteris which are dichotomously branched. The venation of the fronds is reticulate, except in Hecistopteris where there is an open, dichotomous system of veins, and in Monogramma, in some species of which the venation consists simply of a mid-rib. An interesting feature, which has proved to be valuable as a diagnostic character, is the presence of “spicule cells” in the epidermis of the fronds. These spicule cells are elongated cells containing spicules of silica, and their presence appears to be universal in the Vittarieæ. The sporangia are fairly constant in form through-out the group, but their distribution is extremely varied. The roots are characteristically provided with very numerous reddish-brown root hairs, a character shared with other epiphytic Ferns. The Gametophyte is divergent from the common cordate type in all cases where it has been investigated. Such are the main external characteristics of the group under consideration.

Harris is supposed to derive its name from the Gaelic “na hardibh,” a designation signifying “the heights.” The term is appropriate in that the most mountainous parts of the Long Island lie within its boundaries.

South Harris forms a natural geographical division for it is divided, from North Harris by a narrow neck of iand at Tarbert separating the eastern from the western seas. This isthmus is less than half a mile across. In addition to South Harris proper, this memoir deals also with the Isle of Scalpay and neighbouring islets off the north-east coast, the Isle of Taran-say on the north-west, and several islands off the south-west coast in the Sound of Harris, of which the principal ones are Ensay, Killegray, Groay, Lingay, and Gilsay.

Chirocephalus diaphanus, the Fairy Shrimp, feeds on minute suspended particles and organisms that it separates from water currents produced by its limbs. According to Lundblad (1920, p. 41), in the closely similar form, Tanymastix stagnalis (L.), an orally directed current is produced along the mid-ventral line between the trunk limbs which actually carries food particles to the mouth, the current itself being produced by the sweeping action of the anteriorly directed basal parts of the proximal endites of the trunk limbs. According to Storch (1925a, p. 387), the particles are not carried forwards on a current but are swept forwards from limb to limb until they reach the mouth.

The following investigation was commenced, in the first place, to provide information for class use, for, in spite of the fact that thousands of specimens of Squalus acanthias and S. sucklii are used every year in North America, there appears to be no satisfactory account of the blood vascular system of either species available. As the work proceeded, various problems arose which necessitated references to the conditions in other species and the preparation of more detailed dissections than are usually made in class work. It is well known that there is considerable confusion in the nomenclature employed by different authors for even some of the main vessels, and it was soon evident that this is not merely individual preference but, in part, due to a more fundamental lack of agreement as to the precise morphological significance of the vessels themselves. More recent embryological investigations by other workers have, we consider, given a key to the solution of the most important of these problems and have shown that, in so far as the blood-vessels are concerned, the Elasmobranchs lie closer to the other gnathostomatous vertebrates than is generally recognised, and indeed furnish a primitive and generalised type. The time seemed ripe, therefore, to provide a connected account of the vascular system in an Elasmobranch, viewing it in the light of the researches just referred to, and of what is known of the distribution of the various vessels in the sub-class in general. It was hoped that this would provide an epitome that would serve as a basis for future work in the sub-class, and also for comparison with the conditions in higher vertebrates.

The shallow synclinal fold termed the Dalmahoy syncline is situated between the north-western flank of the Pentland Hills and the Murieston fault, the most southerly of the five important easterly and north-easterly dislocations which traverse the oil-shale field of West Lothian. The core of the syncline is occupied by rocks belonging to the lower division of the Oil-Shale Group of the Lower Carboniferous. Intervening between these and the Cement-stone Group is a volcanic zone, probably on the same horizon as the Arthur's Seat lavas, consisting mainly of mugearites and basalts which show their greatest development in the Corston Hill district. Along the whole of the southern limb of the syncline is an extensive spread of Upper Old Red Sandstone, but this formation is almost entirely cut out in the northern limb by the Murieston fault, appearing only in the core of a small anticline near Selms.

The general biology of the Mysids has recently been studied at great length by Blegvad (1922) at Copenhagen. His paper, containing a very complete literature list, deals with Mysis inermis, Rathke, Mysis flexuosa, Müller, and Mysis neglecta, Sars. His comments on feeding are limited, and refer chiefly to the nature of the food that the animals ate in captivity. Gelderd's work (1909) on the digestive system of the Schizopoda describes the course taken by the food through the gastric mill, the masticatory functions of this apparatus, and the method by which the masticated food and digestive juices are brought together, but does not deal with the manner in which the food reaches the stomach. An account, then, of the method by which a mysid collects its food would fill a gap in our knowledge of these forms. The only description, as far as we are aware, of the feeding habits of a mysid is that of Depdolla (1923), who worked on Praunus [Mysis] flexuosus, but his account is superficial and in our opinion very inaccurate. The following paper deals with the feeding habits of a small mysid, Hemimysis lamornœ, about 8 mm. long, which has established itself in the larger fish-tanks at the M.B.A. laboratory at Plymouth. It breeds freely all the year round, and can be obtained from the tanks in abundance, although it is stated to be only a rare visitor in the Plymouth district.

The present investigation was undertaken to throw some light upon the nature and mode of action of the peripheral nervous mechanism of the uterus.

Previous work has demonstrated that the organ, like other viscera, has an autonomic action. That the uterus and vagina can function independently of the central nervous system has been shown both clinically and experimentally by Sir J. Y. Simpson (1), Goltz (2), Riemann (3), Rein (4), Kabierske and Heidenhain (5), Masius (6), and Kurdinowsky (7).

The nervous mechanism of the uterus may be divided into a central and a peripheral part.

So barren of fossil remains is the Cementstone Group of the Scottish Lower Carboniferous Rocks that any addition to our knowledge of the fauna and flora of the period is especially welcome. The list of vertebrate remains is notably meagre, and such as have been found, e.g. at Abden, are generally very fragmentary.

The collection to be described below contained nearly 150 specimens, and includes Plants, Lamellibranchs, Annelids, Arthropods, and Fishes: of these the Plants and Fishes are by far the most important, and constitute more than two-thirds ot the total number of specimens.

Two contrasted oceanographical regions are dealt with in this paper, the fauna of the eastern Pacific being distinct from that of the Marquesas, which are the farthest outliers of the western ocean. In each of these two regions again are two divisions of markedly different ecology, physical conditions in the Galapagos being as great a contrast as could well be to those of the coast of Panama, while the Marquesas Islands differ from their neighbours farther west, which are either atolls, or high islands surrounded by broad reefs, in being without coral deposits of any considerable size, and certainly no true reefs. The corals afford a striking example of the contrast between the two main regions; in Panama the only abundant coral is Pocillopora, in the Marquesas the only “reef” is of Porites, and the other deposits depend upon this genus for their existence. Several species of Pocillopora are abundant in the Marquesas, but are all distinct from those of Panama.