The last major retreat stages of the ice in Scotland have been correlated with the different periods of vegetational history as shown by pollen diagrams. The end-moraines can be divided into two stages, the first stage being the Perth Readvance Moraine, during which the ice extended outside the Highlands. The Aberdeen Readvance Moraine probably also belongs to the same stage. During the second stage, here called the Highland Readvance, valley glaciers reached to the mouths of the Highland valleys where small moraine ridges were formed.

Samples from mainly lake sediments near the moraine were studied, and the pollen diagrams from them show the general vegetational history of the Late-glacial and Post-glacial periods. The same zones as in other parts of the British Isles are used in the diagrams.

The geological and pollen analytical evidence suggests that the Highland Readvance Moraine was formed during the Late-glacial Zone III, and that the Perth Readvance is older than the Alleröd interstadial. The Highland Readvance can now be correlated with the moraines in Scandinavia, the Alps and North America, where they already have been dated.

Lower Carboniferous eurypterids are rare, and consequently the Scottish eurypterid fauna is of importance, in a world setting, because of the number of species of that age which it contains. Since the Scottish forms were originally described, great advances have been made in our knowledge of the Eurypterida which have made necessary the present critical re-examination of all available Scottish Carboniferous eurypterid specimens. Five species, belonging to four genera, are described and illustrated. Fresh evidence of the anatomy of Campylocephalus scouleri (Hibbert) is presented and the wider issues of eurypterid morphology raised by homology with this specialised species are discussed.

One of the writers' main aims has been to help to prepare the way for a new approach to problems in which the natural occurrence of forsteritic olivines is a vital factor. Variation in their shapes and textural relations in minor intrusions, lavas and melts is examined and the historical development of concepts of their growth and resorption, particularly in magmas, is traced. Particular attention is focused on the olivines of picritic, minor intrusions. It is concluded that in the interpretation of olivine shapes there has been discrimination in favour of magmatic resorption rather than skeletal crystallization. From a wide and detailed survey of forsteritic olivines it is established that they tend to grow rapidly and that their phenomenal variation in habit and shape is probably due to a specific growth sensitivity to slight environmental differences. Concepts of the physical conditions leading to skeletal crystallization are briefly reviewed and discussed.

A Summary is given of the field relations, geographical distribution and petrography of twenty-nine dolerite plugs associated with the Tertiary lava plateau of north-east Ireland. All but two of the plugs are composed of olivine dolerite. The exceptions are a pyroxene-rich dolerite and a tholeiitic type containing abundant chlorophæite. Trace-element determinations have been made on specimens from thirteen of the plugs.

Slight but definite chemical differences are shown to exist between the olivine-dolerites and the average Tertiary olivine-basalt lava of the area. The petrogenetic relationships of the two are briefly considered.

A Fertile shoot of Protopitys scotica sp. nov. from the Calciferous Sandstone Series of Dunbartonshire provides the first available information about the reproductive structures of Protopitys which most authors have hitherto regarded as probably a Pteridosperm. The evidence, however, suggests that it is a plant with pteridophytic reproduction. The range in size of the spores suggests too that heterospory with two sizes of spores, megaspores and microspores, was in course of evolution. It is proposed that a new group, the Protopityales, be established to include Protopitys.

A Study of the oögenesis and maturation in four species of melaniid snails, viz. Melanoides tuberculatus—diploid race 2n = 32, M. tuberculatus—polyploid race with 90-94 chromosomes, M. lineatus—polyploid with 71-73 chromosomes and M. scabra—polyploid with 76-78 chromosomes, showed these species to be thelytokous. These are instances of ameiotic parthenogenesis with two equational maturation divisions and are recorded for the first time in molluscs, the only other known instance in the animal kingdom being shown by the cockroach, Pycnoscelus surinamensis. The other parthenogenetic molluscs known so far, viz. Potamopyrgus jenkinsi and Campeloma rufum are also of the ameiotic type but have a single maturation division. No males were ever found in the diploid race of M. tuberculatus and in M. scabra. In the polyploid race of M. tuberculatus and in M. lineatus sporadic males occur, forming about 3 per cent of the population in the former and 0·01 per cent in the latter. Further evidence for ameiotic parthenogenesis is provided by the complete absence of sperms in the receptaculum seminis and brood pouch and also by the absence of sperm elements or any fusion of nuclei in the egg. The chromosome numbers in the different species have been determined from maturation metaphase and have been checked from first cleavage metaphase. Polyploidy is associated with parthenogenesis in three of these species.

Oögonial cell divisions are generally absent. Only three oögonial metaphase plates were seen in the diploid race of M. tuberculatus and one in M. lineatus although a very large number of preparations of the ovary were examined. The author holds the view that the maturation prophase is the continuation of the oögonial early metaphase stage without intervening metaphase, anaphase and telophase. The prochromosomes seen in proleptotene stage are already split and the succeeding stages are characterized by the absence of zygotene, pachytene or any pairing and chiasma formation. Each split chromosome behaves functionally like a bivalent throughout maturation prophase and separates into daughter chromosomes at the first division. The second division is equational as in normal maturation.

This paper provides a comprehensive account of the small spore assemblages of coals in the Limestone Coal Group and Upper Limestone Group (Namurian) of the Lower Carboniferous of Scotland. The coals were obtained from boreholes sunk in the Lothians, Central, and West Fife coalfields. Over ninety species of small spores are figured. Of this number twenty-six are new species. Five new genera—Glomospora, Procoronaspora, Callisporites, Tholisporites and Remysporites—are described. Full descriptions are given of all new genera and species. The assemblages are compared with assemblages of similar age in North America, the U.S.S.R. and elsewhere, and it is shown that the Carboniferous pre-Westphalian microfloras were uniform over wide areas of the earth's surface.

Barrow describes from Glen Clova an important Older Granite intrusion, the muscovite-biotite-gneiss which he holds responsible for the formation of staurolite, kyanite and sillimanite zones of progressive regional metamorphism in the district. He states that the gneiss was filter-pressed during emplacement so that potash was strained off and concentrated in the south-eastern outcrops of the intrusion leaving its north-western portions enriched in soda. He claims that by the same process the separate intrusive areas comprising the gneiss have often been marginally enriched in potash and pegmatite.

The factual basis of the filter-press hypothesis does not withstand careful re-examination. The individual intrusive areas of muscovite-biotite-gneiss bear no marginal zones of potash and pegmatite enrichment like those envisaged by Barrow. The muscovite-biotite-gneiss in its entirety comprises two distinct units, a heterogeneous group of banded quartz-oligoclase-mica-gneisses that were intensely deformed plastically during high-grade metamorphism, and a later series of non-migmatitic microcline-granite intrusions. In neither unit can any regular variation in potash/soda ratio be detected in passing directly from north-west to south-east.

New data are provided concerning the distribution and mode of occurrence of Barrow's metamorphic zonal index minerals. Sillimanite, as fibrolite, often replaces mica and accompanies kyanite in specimens from many localities.

The Schichallion complex is situated in the Central Highlands of Scotland between the villages Struan and Kinloch Rannoch. The area is of considerable geological interest and has been investigated stratigraphically and structurally by E. M. Anderson and Bailey and McCallien. As a consequence of their researches a complete stratigraphical succession has been established. Thus, the metamorphic rocks of the area are classified into the Moinian and Dalradian systems, which are separated by a plane of tectonic discontinuity known as the Boundary Slide. The Moinian rocks are quartz-felspathic granulites, whereas the Dalradian system includes pelitic schists, quartzites, limestones as well as a variety of meta-igneous rocks.

In his previous research the present author has established the tectonic history of the complex. In particular three episodes of folding (F1 to F3) and a much later episode of faulting (F4) were recognized. Of these the F3 episode is of least significance. Consequently, events after the F2 movements can be in many cases regarded as post-folding.

The present contribution is concerned essentially with the mapping of the metamorphic zones (garnet and staurolite-kyanite) and with a detailed study of the mineralogical evolution of regionally metamorphosed rocks within these zones.

In the field it is possible to prove that the staurolite-kyanite zone is essentially post-folding, since the kyanitepegmatites are found to cut across the minor F2-folds. In this respect textural studies confirm the field observations. The study of the internal inclusions in garnets indicates that the garnet zone has a much longer history, since pre-F2 garnets are found in the southern part of the complex and throughout the central part of the area syn-tectonic F2 garnets are apparent. The pre-F2 garnets contain a very fine-grain F1 fabric. Hence the garnets in relation to the F1 movements are post-tectonic. Thus, the regional metamorphism can be subdivided into three phases: the F1 metamorphism, the F2 metamorphism and the post-F2 metamorphism. The latter, on structural evidence appears to be at least in part contemporaneous with the F3 movements.

The meta-igneous rocks of the area are grouped into the hornblende-schists and granular epidiorites. The hornblende-schists appear to have suffered deformation and recrystallization during F1 and F2 episodes of movement. On the other hand the granular epidiorites are later than the F1 and the F2 movements. Although in the southern parts of the district the epidiorites have been slightly deformed, elsewhere they preserve the original ophitic texture and cut across the F1 and F2 folds. The deformation in the south is attributed to the effects of the F3 folding. The epidiorites have been evidently emplaced as dolerites after the F2 movements and before the F3 metamorphism.

The localized retrogressive metamorphism is associated with the F4 movements, which are responsible for the Loch Tay Fault. The Fault is later than the minor intrusives associated with the Younger Granites of the Scottish Highlands and is suggested to be of a Lower or Middle O.R.S. age.

On the basis of the chemical composition of the plagioclase felspars it is proposed to include all the staurolite and kyanite bearing rocks into the epidote-amphibolite facies. In this respect temperature and the hydrostatic pressure are assumed to have been the main factors, since similar minerals came into existence during static and dynamic stages of metamorphism alike.

In the rare males of the polyploid race of Melanoides tuberculatus, which constitute about 3 per cent of the population, spermatogenesis has been studied in detail and compared with certain stages of spermatogenesis in the rare males of M. lineatus, which constitute 0·01 per cent of the population. The occurrence of the rare males in these parthenogenetic Melanoides provides an exceptional opportunity for studying the pairing behaviour of the chromosomes and for obtaining a better understanding of the probable nature of the polyploidy involved. During spermatogenesis, the two usual meiotic divisions occur, but the different stages show univalents, bivalents, quadrivalents and bridge fragment configurations. Degeneration of sex cells occurs at different stages, but mostly at the spermatid stage and the sterility of the rare males may be said to be chromosomal. The significance of the various abnormal meiotic phenomena is discussed and it is suggested that autoallopolyploidy is involved. A conjectural scheme of the possible origin of the autoallopolyploid M. tuberculatus is also suggested and the interrelationships between parthenogenesis, polyploidy and hybridity discussed.