Recent work has directed much attention to the subject of feeding mechanisms and digestive enzymes in the Invertebrates.

The groups worked on previously have been chiefly the Mollusca and the Crustacea, and it was felt that a study of the Polychætes in this connection would be of considerable interest in itself, as well as for comparative purposes. An examination of the literature showed that the amount of detailed work on the Polychætes from the physiological point of view was extremely small, and, in the case of the digestive processes, out of date. A study of the feeding mechanisms and physiology of digestion in Polychaetes has therefore been begun, choosing a filter-feeding form as a starting point, so that a direct comparison can be made with such Molluscs as Mya arenaria and Ostrea edulis, which feed on similar material.

Sediments of Carboniferous age occur in Kintyre in the district between the high ground of Southern Kintyre and the ridge of Northern Kintyre. The low ground stretching from Machrihanish to near Campbeltown is known as the Laggan of Kintyre. The Laggan runs in a series of terraces from the Atlantic to within a mile of Campbeltown, where the terraces give place to higher rounded knolls rising to a general height of 200 feet, and separated from each other by the highest raised beach. The chief platform in this plain is formed by the Machrihanish Water and its tributaries, the Backs and Chiscan Waters, and on both sides of this platform are the three terraces separating the 25-foot, 50-foot, and 100-foot raised beaches from each other and from the alluvial plain of the rivers. The 100-foot beach runs a considerable distance up the valleys leading to the higher ground to the north and south of the Laggan. To the extreme west, 3½ miles of sand dunes, higher than the plain behind them, give slight protection to the greatest stretch of cultivated land in Kintyre. Near the centre of the plain is a circular peat moss known as the Durry Moss.

The main object of tho present paper is the consideration of the structure of the Central and S.W. Highlands as shown up by the metamorphic condition of the beds. This metamorphic condition has boon studied over the length and breadth of the country, mapped and deduced from very many outcrops in all districts. Sometimes it was possible to superpose the the details respecting the metamorphism upon the 1-inch maps of the Geological Survey, but in many other cases the areas were mapped upon the 6-inch scale. Naturally this work has taken a long time, for it has necessitated the collection of many thousands of specimens, and nearly 3000 rocks have been sliced and examined, since it is not always possible to define the limits of a metamorphic zone with precision by field work alone, and many rock types were encountered that rendered a more careful study advisable than was possible from the mere examination of a hand specimen.

The following report deals with the systematics and distribution of molluscs collected in and around certain lakes in Jasper National Park, Alberta, Canada. For the sake of completeness some records published by Baker (2) are also included. The investigations of which this forms a part were made under the direction of Professor Charles H. O'Donoghue at the request of the Biological Board of Canada, and I desire to thank him for his encouragement and help throughout.

In a previous communication an account was given of the sedimentary series exposed along the eastern coast-line of the Shetlands from Rova Head to Sumburgh Head. Fossil evidence was adduced which enabled the position of these beds in the Old Red System to be fixed more definitely than had hitherto been the case; they were shown to be partly of Middle, partly of Upper Old Red Sandstone age, the base of the Rova Head Conglomerate being taken as the dividing line. Since the publication of that paper additional fossils have to be recorded. Examination of the numerous specimens of the Microbrachius from the fish-beds of Shetland fails to reveal any specific distinction between that form and Microbrachius dicki Traq. occurring in the John o' Groat's Sandstone Group, and the Eday Sandstones; it is therefore an important addition to the chain of evidence linking up the Shetland horizon with those of Orkney and the Mainland. An additional record of little stratigraphical value is that of Coccosteus (sp. indet.), a single plate of which was found by Professor W. H. Lang at a horizon slightly below the fish-bed at Shingly Geo, Dunrossness.

The stem of the various species of Piper is characterised by its anomalous vascular structure. Medullary bundles are present throughout the genus, and there is, in addition, a modified type of secondary thickening. During an investigation of these features my attention was called by Professor Montagu Drummond to certain endodermal characters which appeared to be of considerable interest and which suggested that a more extended investigation was desirable.

Reference to the literature showed that the few earlier investigators of the genus had concerned themselves mainly with the peculiarities of the vascular system. J. E. Weiss (18) made some general observations on the occurrence of the endodermis in the genus, but no mention of the genus is made in the comprehensive monographs by Kroemer (8) and by Mylius (10) on the endodermis, or in the writings of Van Wisselingh. It would appear therefore that no detailed investigation of the endodermis in the genus has been carried out, in the past.

The work described in the following pages was carried out in the Department of Zoology of the University of Edinburgh and at the Marine Laboratory, Plymouth. It is my pleasant task to thank the British Association for the use of their table at Plymouth, and the staffs of the Plymouth Laboratory and of the Department of Zoology at Edinburgh for help and advice; in particular, I would thank Professor J. H. Ashworth, F.R.S., under whose direction the work was carried out, for his continued aid and interest at every stage.

The animal which was used throughout the investigation was the common razor shellfish or spoutfish of our coasts, Ensis siliqua (Schumacher). The specimens studied at Edinburgh were obtained from a sandy bay at Port Seton, about ten miles below Edinburgh on the Firth of Forth; at Plymouth they were got from the east bank of the Salcombe Estuary. At both places razor shellfish were abundant at the low-water mark of spring tides, and at both Ensis siliqua was the sole species obtained.

For histological purposes small- whole animals, which were very rare, and small pieces of tissue were fixed in Bouin's fluid, in E. Allen's chromic Bouin with urea, or in corrosive sublimate and acetic mixture, and sections, cut 8 μ and 12 μ thick, were stained with Heidenhain's iron alum hæmatoxylin or in Delafield's hæmatoxylin and counter-stained with eosin.

North of Skye the waters of the Minch conceal Tertiary igneous rocks, probably of great interest, the nature of which may be surmised only from the study of a few small skerries or islands projecting above sea-level. The group of the Shiant Isles is the best known and most interesting of these, and has been described elsewhere; but the more southerly islets, which form the subject of the present communication, are not without importance in themselves, besides forming a useful geological connecting link between the Shiants and Trotternish. As shown in the sketch map (fig. 1), they comprise the little archipelago a league off the Trotternish coast, which will be referred to as the Fladda group; the island of Trodday, two miles north-east of Rudha Hunish in Skye, and three small rocks or skerries lying close to the track of the Harris mail steamer.

Bellerophontidæ occur in considerable numbers at certain horizons in the Scottish Carboniferous rocks. Many forms are represented, but few have been described or figured (see Historical Account, Section III). In undertaking the study of these fossils the writer's object was limited, primarily, to figuring and describing the Scottish forms and ascertaining their value as stratigraphical indices in the Scottish Carboniferous rocks. Many forms from the shaly facies have been recorded in Scottish stratigraphical literature under the names of English and Belgian species of limestone facies. Investigation proved that most of these records were invalid, the determinations being erroneous, and that revision of all the Anglo-Belgian Bellerophontidæ was necessary in order to define the Scottish forms. The present memoir embodies the results of the wider investigation.