In a new synopsis of the family Limapontiidæ the differences between Limapontia capitata and L. depressa, which may sometimes be mistaken for one another, are specially noted. These two species and Acteonia cocksi, the remaining member of the family, are sap-suckers that feed on the cell contents of green filamentous algæ. The cells are slit open one at a time by the leading tooth of the radula and their contents drained. The host plants of A. cocksi and L. capitata are marine Cladophora spp.; L. depressa feeds on Vaucheria. The size of the buccal mass varies according to the host plants. The subterminal position of the anus in L. depressa is an adaptive feature. The reproductive system of A. cocksi is described and compared with those of the other two species. During copulation both A. cocksi and L. capitata transfer sperm by hypodermic impregnation: sperm are injected by means of a penial style into a closed bursa copulatrix. The bursa of L. depressa opens to the exterior by a short duct and the penial style functions as a conducting pipe. Reasons are given for suppressing the genus Acteonia, Quatrefages, and including A. cocksi in the genus Limapontia, Johnston.

A Brief description of the early stages of floral organogenesis in Primula bulleyana is followed by an account of the formation of flowers from experimentally incised primordia. The nature of the floral parts that develop alongside a median incision is related to the developmental stage of the flower primordium at the time of its bisection. The observations are discussed with reference to the determination of the parts of the flower.

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.

The changes in the vascular pattern of the pregnant rat uterus at placental sites and the intervening areas, have been studied radiologically and by injection techniques during the period of pregnancy. A description is given of the development and final pattern of the maternal placental blood channels. From the 15th day onwards wide variations are found in the vascular filling of placentæ after arterial injection. Possible mechanisms for the control of blood flow to placental sites are discussed.

An account is given of the distribution and zonation of the moie important plants and animals found on rocky shores. Particular attention is directed to the variation which occurs in the dominant midlittoral communities of exposed shores, and to the wide range of low-level populations found in the sheltered sea-lochs.

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.