At a height of 4400 metres in the Nepal Himalaya, a vitreous and vesicular rock was discovered by J. S. Scott in 1949. It is located along a line of intense brecciation in a region of high-grade granitic gneisses.

This paper is based on a laboratory examination of a specimen of this rock and a few other specimens from the same locality. As some of these specimens have no exact counterpart hitherto described, a new but self-explanatory nomenclature has been employed in their description. The new rock-types—breccia with a cryptomylonite matrix, cryptomylonite and hyalomylonite—seem to represent, in this order, progressive stages in the degree of vitrifaction.

Biotite, alkali feldspars and quartz participated in the vitrifaction, which was due to high temperatures and heat developed by friction between these minerals in a triturated rock medium of low thermal conductivity.

An important function is attributed to the biotite which, in the more vitreous parts of the rocks, tends to disappear entirely. It is suggested that selective melting of this biotite has yielded to the liquid ferrous iron, and fluxing by this component is believed to be a critical factor although water must also be considered. Chemical analysis revealed no significant quantity of water in the glass-rich rock, but the development of vesicles and bubbles implies that there was more water in solution prior to its ebullition as a vapour phase.

There appears to have been a remarkable variation in temperatures within extremely short distances, and there is some evidence that the specific melting points of the alkali feldspars may, in a few exceptional instances, have been attained.

A survey has been made of the condition of the mantle cavity in populations of Lymnœa (Radix) peregra (Müller) and Physa fontinalis (L.) living in a range of depths and habitats in Loch Lomond. In many populations, including some in relatively shallow water, the mantle cavity remains water-filled throughout life. Where the cavity contains a gas-bubble, micro-gas-analysis (using a modification of Krogh's methods) has revealed that in some cases the gas composition is such that the bubble could be used as a physical gill, while in others such use is unlikely. Other observations on respiratory behaviour of the two species are reported, and growth-changes are noted in the surfaces available for cutaneous respiration. The study is discussed in relation to previous work on the respiration and ecology of freshwater pulmonate snails.

Recently discovered fragments of the armour of the ostracoderm Corvaspis are described, together with similar material from Vestspitsbergen and Podolia. The fossils have been obtained from Lower Old Red Sandstone deposits of Upper Downtonian–Lower Dittonian age. Large, thick, median plates, small irregular plates, orbital and ridge plates, and small, thick polygonal scales are present amongst the material. The characteristic external ornamentation of smooth, narrow ribs of dentine and a marginal band of small, smooth irregular tubercles is present on all plates. Two species are distinguished by their slightly differing ornamentation: Corvaspis kingi is known from the three regions named, C. graticulata sp. nov. comes from somewhat higher in the Vestspitsbergen sequence, and bears a finer ornamentation. A new family of heterostracans is erected to contain the genus, which in general structure may have been somewhat akin to the Drepanaspidæ, although no complete reconstruction can yet be attempted.

A detailed consideration of the morphology, peritoneal and topographical relations, blood supply and certain aspects of the histology of the alimentary tube are considered in these two rare lemurines, the anatomy of which has hitherto been very incompletely known. Evidence is presented of the structural apartness of Hapalemur from Lepilemur and Lemur and therefore for its separation in a separate subfamily of Lemuridæ. Differences between Hapalemur and Lepilemur are seen in the stomach, cæcum, colon, spleen, liver and gall-bladder. The resemblance of the spleen of Hapalemur to that of the marsupials proclaims its primitive status, while the fissuration and relative sizes of the main hepatic lobes show noteworthy differences in the two genera. In some respects Hapalemur approaches the Cheirogaleinæ, but cannot be included by definition within that subfamily.

The hoatzin (Opisthocomus hoaziri) embryos are of special interest because the species is the only representative of its family and sub-order, and is well known to possess important anatomical features comparable with the bird-like reptiles. Eleven hoazin embryos collected by Dr G. S. Carter in British Guiana have been examined. These range in development from a stage having nine mesoderm segments—equivalent to a fowl embryo of approximately forty hours' incubation—to a single specimen ready to hatch. The earlier embryos resemble the corresponding stages in the development of other birds, but the oldest embryo shows features characteristic of the type and has been dissected. Points in the anatomy of this specimen and their bearing on previous observations on hoatzin embryos are discussed.

The contrasting geological and topographical features of different regions of Loch Lomond and its watershed are reflected in the nature of the bottom deposits of the lake. This paper presents a survey of the lake bed with the object of determining the extent of its regional variety, and confirms the validity of regarding the lake as divisible into two primary regions. The two primary regions, “upper loch” and “lower loch”, are clearly distinct, but the case for the separation of part of the lower loch as a third, intermediate, region cannot be dismissed without further investigation. From a comparison of the bottom deposits, an attempt is made to show the advance in trophic state made by the lower loch over that of the upper.

Thin sections of the spinal ganglion of the rat were cut and examined with the electron microscope. Two main types of nerve cell are described. Type A with equal electron density of nucleus and cytoplasm. The cytoplasm contains large aggregates of Nissl's substance discretely scattered throughout the cell, mitochondria and osmophilic granules. Type B with a “light” nucleus and a “dark” cytoplasm. The cytoplasm is closely packed and homogeneous so that it is difficult to separate out the various cytoplasmic elements.

There is a well-marked nuclear membrane about 500 Å thick and characteristic strawberry nucleolus.

The capsular cells are closely applied to the nerve cell with no intervening boundaries. A system of cytoplasmic filaments—the “endoplasmic reticulum”—is present in the intercellular regions.

There are nerve fibres with lamellated myelin sheath, axolemma, Schwann cells and Schwann membrane.