The early development of the mammary glands and of hair follicles in the mouse and the rabbit has been investigated by means of mitotic counts, by histochemical methods and by cultivation in vitro. In the first stage of the formation of both types of rudiment a thickening of the epidermis appears as a consequence of an aggregation of cells, not of a local elevation of the mitotic rate. During this stage alkaline phosphatase is absent from the cells and the content of ribose-nucleic acid reduced. Both these substances appear in higher concentrations later, and their relation to processes of growth and differentiation is discussed. Essentially similar phenomena are found in rudiments cultivated in vitro, which, however, frequently suffer a degeneration by a process of keratinisation.

The stratigraphical succession of the Jurassic rocks of Eathie (Cromarty) is described and a list of the fossils collected by the writer from the Kimmeridgian beds given. The fauna, which is of mixed Boreal and Mediterranean affinity, shows that the strata belong to the three basal Eo-Kimmeridgian ammonite zones proposed by Spath. The occurrence of an abundant microfauna is recorded and the palæontology of the varied molluscan forms is discussed. Three new lamellibranch species are described. A short account of the Upper Oxfordian beds which outcrop at Bow Buoy Skerry, 1 mile south of Eathie, is given.

Kentuckia, from the basal Carboniferous, is the earliest bony fish in which neurocranium and dermal skeleton are well known. The dermal bones show that it belongs to the central family Palæoniscidæ of Berg. They have no obvious generalised characters, however, and are chiefly distinguished by a deeply embayed hind margin to the skull roof, no dermohyals and an elongated postorbital bone. These features suggest a greater affinity with the few known Devonian types than with those of the Carboniferous.

The neurocranium has a considerable likeness to Watson's Kansas Palæoniscids A and B, and confirm Watson's view that this is the fundamental type of actinopterygian cranium. Kentuckia is slightly more generalised than the others in having a paired myodome and a less excavated dorsal surface. The notochord in all three has a long anterior extension like that shown in Pteronisculus (Glaucolepis) of the Eo-Trias by Nielsen. This latter fish is similar to the earlier ones if allowance is made for a greater proportion of cartilage. In the discussion reference is also made to the following: the degree of ossification of these fishes, the nature of the cranial fissure and its homologues, the distribution of the third, fourth, fifth and seventh nerves, and the origin of the cranial wall in the orbitotemporal region.

Certain additions are made to Watson's account of Palæoniscids A and B, particularly concerning the interior of the braincase. A new form, C, is also described.

An interpretation of the Tertiary rocks of the area, which are shown to be denudation relics of a gigantic volcano, is found by following the actualistic principle, that is by interpreting the unknown with reference to the known or actual. “Actualistic”, i.e. with reference to actual causes—commonly used by continental geologists—is chosen in preference to “uniformitarian” since the latter stands in contradistinction to “catastrophic”, and is not, therefore, altogether appropriate to some of the more violent aspects of volcanic activity. Gabbros and granophyres, hitherto thought to be plutonic intrusions emplaced within Caledonian granodiorite, are shown to be highly metamorphosed basaltic and rhyolitic lava-flows, agglomerates and tuffs, together with some gabbro sills. These rocks form a layered series which is almost horizontal at Slieve Gullion, and dips at various angles at Foughill and Carrickcarnan. A Tertiary ring-dyke of granophyre and felsite encircles the layered rocks and outlines a caldera within which the basaltic lavas (including pillow-lavas) of Slieve Gullion accumulated. During the formation of a later caldera these lavas became inset within the underlying Caledonian granodiorite. The acid layers of Slieve Gullion represent rhyolites, incandescent tuff-flows, and agglomerates, the materials of which were derived from the Caledonian granodiorite. The time of eruption of these acid rocks is correlatable with periods of caldera formation.

The layered series is dissected by arcuate faults, and contacts previously thought to be intrusive are now demonstrated to be faulted. Transgressive granophyres follow the faults and form intrusion-breccias and net-vein systems with the layered series. Evidence is presented for concluding that these granophyres originated as glassy acid tuffisite—an intrusive pyroclastic rock (Cloos, 1941)—derived from the basement Caledonian granodiorite, and emplaced by rising gas-streams. That the gas sometimes had a temperature high enough to fuse basalt is witnessed by the fact that the basaltic rocks commonly become exceedingly fine grained where they adjoin transgressive granophyre. Such fine-grained edges are cross-cutting to the layers and cannot therefore be interpreted as normal chilled edges. Hybrid rocks, e.g. marscoite, are associated with the transgressive granophyres. They are shown to represent mechanical mixtures of acid tuffisite, carried upwards by rising gas-streams, with fragmented (tuffisitised) and partially fused basic material derived from the walls of the channels. The transgressive granophyres and associated hybrids are related in origin to incandescent tuff-flows, and are regarded as marking the routes by which such flows reached the surface.

The metamorphism of the basaltic flows, and the transformation of the acid layers and transgressive acid tuffisites to granophyre, were probably accomplished during the pneumatolytic and hydrothermal phase of volcanic activity. Transformation of the acid rocks to granophyre involved introduction of K and Si, and removal of Na, Al, Fe, Ca, Ti, P and Mn. Similar chemical interchanges transformed basaltic rocks at Foughill and Carrickcarnan to quartz-dolerites. The subtracted materials have been located in small-scale basic fronts margining granophyres; within masses of gabbro that sank within gas-tuff streams from higher levels; and in dispersed form within the basic rocks of Slieve Gullion.

A Critical survey is given of the spirit-preserved material of Marsupialia in the Royal Scottish Museum, with special reference to the fœtal stages.

Of the crab-eating opossum, 12 mm., 16 mm., 20 mm., 30 mm. and 70 mm. stage pouch-embryos are discussed in detail, and compared with stages already known for D. marswpialis virginianus. A similar series of Dasyurus quoll, varying from 12·2 mm. to 34 mm., is considered, followed by notes on adults of some of the less well-known Dasyuridæ. Three pouch stages are studied in Peramelidæ and comparison made with data in the literature. In the Phalangeridæ fœtal stages of Pseudocheirus lanuginosus, Schoinobates volans, Trichosurus vulpecula and Acrobates pygmœus are included. Macropodidœ are represented by Macropus robustus stages ranging from 16 mm. (3·4 weeks old) to 138·7 mm.

The type material of Orthocera gigantea J. Sowerby 1819 is refigured and redescribed. Specimens referred to this species by J. Phillips, J. Fleming, F. McCoy and F. S. Wallis have similarly been reinvestigated. The counterpart of the type of Actinoceras simmsii C. Stokes 1840 is also illustrated. Numerous other specimens from England, Scotland and Ireland have been studied. The material is found to be referable to the genus Rayonnoceras Croneis and to embrace a number of species. The calcification of the siphuncular structures is found to be variable in this genus.

The mammalian hair-fibre, together with the “inner root-sheath” (i.e. the axial layers of the follicle wall), grows upward by a proximal addition of cells. Changes in the inner root-sheath are responsible for the final shape and surface sculpture of the fibre. At its distal limit the inner root-sheath disintegrates owing to the effect of a de-keratinizing chemical agent.

A bent, undulated, or “crimped” fibre is due to a differentiated progress of the changes leading to keratinization of the “fibre cortex”. The cells which give rise to a “medulla” are different chemically and less compressible than cortical cells.

This is a study of the structure and biology of the lamellibranch Venerupis pullastra (Montagu) from the early larva to the spat stage. The larva is identified, and the functional significance of the changes that occur during metamorphosis from the larva to the spat is considered. Organ development in the spat up to a length of one millimetre is described. The free swimming larva is studied from the point of view of seasonal abundance, length of pelagic period, vertical distribution and diurnal migration. Spatfalls both on artificial and natural bottom are studied, and the results indicate a possible cause for the high mortality in the early stages of marine invertebrates with this type of reproduction.