Flounders grew much more slowly in 1944 than during the previous 2 years. From October 1943 to October 1944 their mean size increased from 7·9 cm., 6·8 g., to 12·7 cm., 23·6 g., an increment which was if anything smaller than under normal conditions. The reason for the reduction in growth rate is attributed to the increasingly unfavourable hydrographic conditions resulting from the prolonged closure of the dam, in particular to the high H2S concentration, the high pH and the low oxygen concentration of the water.

In the autumn of 1944 the sluice gate of the dam was opened for several months. In 1945/46 the growth of stock III flounders was very rapid. They reached a mean size of 32·3 cm., 409 g., in March 1946 and 36·8 cm., 580 g., in March/April 1947. Native flounders reached a mean size of 30·6 cm., 353 g., in 2 years.

An account is given of the further changes in the bottom fauna of a fertilized sea loch (Loch Craiglin) from 1944 to 1947, and the results are compared with those obtained from 1942 to 1944.

The bottom fauna density fell markedly during 1944, despite the addition of very large quantities of fertilizers. Unfavourable hydrographic conditions, especially low oxygen tensions, are considered to be responsible for the decrease.

A description is given of a number of observations ahd experiments on the larvae and colonies of Tubularia. The experimental material could best be referred to the species T. larynx Ellis & Solander. Its characters are not wholly consistent with the diagnosis of this species, but the differences which exist are not great enough to warrant the erection of a new species.

Liberation of the actinulae takes place more freely in darkness than in light, and there is evidence which suggests that it only occurs in still water or in weak currents.

The seven species of small copepod common in Loch Striven have been studied from vertical tow-net hauls taken there throughout the year 1933. These copepods were Pseudocalanus minutus, Paracalanus parvus, Microcalanus pygmaeus, Centropages hamatus, Temora longicornis, Acartia clausi and Oithona similis.

In general, the copepods began to reproduce about the time of the spring diatom increase in March or April, and produced a succession of broods throughout the summer; apart from the first these broods were not as a rule so clearly marked as in Calanus. Microcalanus begins to breed before the spring increase and has clearly marked broods like Calanus.

Modifications are described to the penetrometer originally designed by Chapman & Newell (1947) for the measurement of the resistance to penetration of marine soils.

An account is given of qualitative and quantitative tests made during the study of the thixotropy and dilatancy of the muddy sand of the Arenicola region of the shore at Whitstable. The results of tests made with the dilatancy viscometer originally used by Freundlich & Röder are shown not to be in clear agreement with the observed behaviour of the soil.

The mathematical analysis of bimodal distributions is very complex. Karl Pearson (1894) investigated the problem and developed equations for the purpose; but found them unsolvable as the ‘majority [of the relations] lead to exponential equations the solution of which seems more beyond the wit of man than that of a numerical equation even of the ninth order’. He did indeed evolve an equation of this order and used it to analyse a few bimodal distributions, but the arithmetic involved was very laborious. Later he (Pearson, 1914) gives a table for ‘Constants of normal curve from moments of tail about stump ’which, as he describes in the introduction, occasionally permits a rough analysis of a distribution which is known to be bimodal. This method is much more rapid than the solution of the nonic equation, but ‘owing to the paucity of material in tails and corresponding irregularity there will be large probable errors’. Gottschalk (1948) discusses the question and shows that inthe special case where the bimodal distribution is symmetrical comparatively simple solutions can be found.

A method of estimating the maximum quantity of manganese available to plants in sea and fresh waters is described.

Samples of sea water collected off Plymouth in 1948 contained 0·7–1·0 mg. Mn/m.3 in solution plus any particles soluble at pH 4·6. After storage and sedimentation of particulate matter, the quantity decreased to 0·0–0·25 mg./m.3

Samples collected off the Isle of Man, an area with a rich summer population of flagellates, contained 2·0–2·6 mg./m.3

The river Yealm, south Devon, on leaving Dartmoor contained 1 mg., and after passing through agricultural land 10 mg.\m.3

Lakes and streams in the English Lake District contained 6–40 mg.\m.3 The least fertile waters contained the least soluble manganese.

Considerable differences were found in the size compositions of populations of Asterias rubens off Plymouth. These differences were not correlated with age.

Laboratory observations on rate of growth showed that well fed starfishes grow fast during summer and autumn and somewhat slower in winter. Poorly fed starfishes did not increase in size, but were able to survive for long periods with a minimum of food.

Erosion of Dawlish Warren, at the mouth of the Exe Estuary has resulted in a redistribution of sand, which has come to lie in close proximity to certain of the original mud banks.

Quantitative collections of the macrofauna were made along a traverse passing from the newly deposited sand to the old mud bank, stations all being at about half-tide level.

Measurements of salinity, temperature, pH, currents and wave action show that these are similar for all stations. Thus it has been possible to observe the distribution of the fauna in relation to the type of soil without the usual complications due to differences in other factors.

Six species of rotifer, including one oceanic species and representing four genera, are recorded for the first time from Plymouth. Remarks are made on various interesting features of their anatomy, details are given of their times of occurrence at Plymouth, with notes on their location and known distribution in other parts of the British Isles, and in foreign waters.

Attention is called to the apparent poverty of the Plymouth marine and brackish-water Rotifera as compared with that of Liverpool, investigated at length by Galliford. It is stressed that no exact conclusions as to the reason for this can be made until after a more exhaustive survey, as some likely habitats adjacent to the Sound were not investigated. Attention is also called to the caution which must be exercised in terming rotifers marine, as most of those collected in coastal waters appear at present to be confined to areas where a considerable amount of fresh water is discharged into the sea. At least two species, one of which occurs in the Sound in May, are known to be truly oceanic, having been found in mid-Atlantic.

It is suggested that ‘brackish’ and ‘estuarine’ are the terms most applicable to the majority of coastal rotifers in the present state of our knowledge.

Six marine flagellates, used as food in the rearing of the larvae of Ostrea edulis L., are described.

One belongs to the Chlorophyceae, Pyramimonas grossii n.sp. (Polyblepharidaceae); four belong to the Chrysophyceae, Chromulina pleiades n.sp. (Chromulinaceae), Isochrysis galbana n.g., n.sp., Dicrateria inornata n.g., n.sp., D. gilva n.g., n.sp. (Isochrysidaceae); and one belongs to the Cryptophyceae, Hemiselmis rufescens n.g., n.sp. (Nephroselmidaceae).

A form of reproduction in a palmelloid phase, not previously described, is recorded for the Isochrysidaceae.

The post-larval sand-eels (Ammodytidae) occurring in the Celtic Sea and Plymouth area are identifiable as Ammodytes lanceolatus, A. tobianus, A. marinus (not previously recorded from the area), and a fourth species of Ammodytes, the adult of which, it is concluded, is not yet known.

Adult Gymnammodytes semisquamatus (not previously recorded from the Plymouth area), the young of which are not yet known, increases the number of species in the area to five.