In a previous paper (Steven, 1948), brief accounts are given of three distinct mackerel fisheries that at one time existed in the south-west of England—an inshore fishery in the English Channel carried on from Plymouth, a deep-sea fishery from Newlyn, Cornwall, and an inshore fishery from Newlyn and some other Cornish ports. One of these fisheries, the Plymouth one, no longer exists. After a few years of considerable activity following the termination of the 1914–18 war, this fishery collapsed in 1924 (Table I) and came entirely to an end a few years later. The small quantities of mackerel landed at Plymouth in subsequent years have been incidental catches by vessels fishing for herrings or pilchards.

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.

A bottom-sampler is described for use under open-sea conditions, particularly where the bottom is of sand or coarser material.

It takes a sample of 1/20m.2 area of semicircular cross-section and maximum depth 15 cm. There is probably little loss of material while hauling and no danger of the apparatus losing soil through being wedged open by shell fragments, etc. The instrument weighs over 45 kg. and is weighted to n o kg. in use.

There are few adequate descriptions of British members of the ascidian family Didemnidae and little attention has been given to the larvae. In the autumn of 1947 a didemnid was collected from the intertidal zone in the Menai Strait, North Wales. This ascidian agrees superficially with Leptoclinum maculosum Edwards, as figured by Milne Edwards (1842) and by Alder & Hancock (1905–1912), although differing somewhat from the diagnosis of Didemnum maculosum (Edwards) given by Harant & Vernières (1933). It is closer anatomically to the D.fulgens (Edwards) of Harant & Vernières, but differs in colour. In most features the colony and zooid closely resemble the descriptions given by Michaelsen (1923) for his species D. helgolandicum Michaelsen, and it is probable that this is the species to which it should be assigned. Nevertheless, the name D. maculosum has been retained since it is under that name that it has probably appeared in most faunistic lists.

Until recently all accounts of didemnid larvae have described three anterior adhesive organs. This was the number given by Giard (1872) for Diplosoma gelatinosum Edwards, and by Lahille (1890) for Trididemnum tenerum Verrill and Polysyncraton lacazei Giard. Berrill (1947), however, has described a new species of didemnid, Trididemnum alleni Berrill, the larva of which has only two anterior adhesive organs, a condition not previously found in any ascidian larva.

The larva (Fig. IA) of the colonies found in the Menai Strait resembles that of T. alleni in many features. The trunk is about 0.35 mm. long from the tip of the adhesive organs to the base of the tail.

The feeding rate of small specimens of Mytilus edulis (L.) has been determined in suspensions of colloidal graphite (‘Prodag’, grade ‘C’, and ‘Aquadag’, grade ‘S’), of flagellates, and of Nitzschia dosterium. The feeding rate was measured as the volume of water cleared from particles per unit time. In graphite suspensions, with particle size of about 4–5μ, as a rule only a small percentage of the particles was retained by the gills, whereas flagellates of about the same size were normally nearly all retained.

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.

During the daily maintenance work of a large aquarium many casual observations are made on the habits of the inmates. These are sometimes worthy of record, though too slight in themselves to justify separate papers each under its own distinctive title. It has, however, been thought fit to bring together in the form of a series of notes some of the more interesting of these observations. It is not intended to discuss each with full reference to the comparable literature; rather are they presented as raw material for the use of other investigators in their own specialized fields. Most of these observations have been made since the re-establishment of the Plymouth aquarium in 1946 (after its war damage), and up to the date of writing, November 1948.

Certain marine algae were treated with sea water containing carrier-free radioactive strontium (mixture of Sr89 and Sr90), to test whether these ions were taken up by the weeds.

At the same time the behaviour of radioactive yttrium (Y90), which occurred as a short-lived daughter-product of Sr90, was investigated by the expedient of studying the ‘decay’ characteristics of specimens of water and weed.

Promising possibilities of this technique, by which an isotope is made available for study by applying its parent substance, are pointed out.

Radioactive strontium is extracted from sea water by the brown sea-weeds, in particular by Fucus serratus.

It is held that this effect is simply a result of ionic exchange, and that the algae regularly contain many times as much strontium in their cell fluids as exists in sea water.

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.

Records are given of the numbers of barnacle larvae obtained from samples of water pumped through a plankton net. Several series of hauls were made at intervals over the time of year when barnacle larvae are abundant.

The numbers of the cyprid larvae of Balanus balanoides in the surface waters show a diurnal variation, being markedly less during the hours of darkness. This conclusion may also apply to the cyprids of B. crenatus and Verruca stroemia, but the numbers of these larvae were too small to permit reliable conclusions to be drawn. There is some evidence that similar diurnal variations occur in larval stages other than the cyprid.

It has been shown that the main factor which influences the local distribution of the lugworm at Whitstable is the depth of the muddy sand overlying the clay stratum below.

In places this clay is furrowed by straight channels which are revealed only by the arrangement of the lugworm castings. These are more numerous along the channels.

Migration of adult lugworms has been shown to occur, most freely in the spring.

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.

Larvae with three and four chaetigerous segments and also an early post-larval stage of Arenicola marina are described with figures. These are all bottomdwelling stages enclosed in mucous tubes and were collected from the pebble and Fucus zone at Whitstable.

The rinding of these larvae furnishes additional evidence for the view that, except when migrating in the water to new habitats, the lugworm possesses no pelagic larval stage in its life history.

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.

When sea water is stirred with mud and then filtered, its phosphate concentration may either increase or decrease. When the filtrate is ultrafiltered, the concentration increases.

Similar increases occur when the filtrate is stored in glassware, and these obscure any effects of the presence of colloidal material. On storage concentrations rise for about 2 hr., and then fall to as low as 2 mg./m.3 P2O5 in 18 hr.

Rise and fall are both prevented by the addition of formalin, chloroform or toluene, and are more noticeable in small containing vessels. Both occur during either day or night, and when temperatures are either rising or falling.

Experiments are described which suggest that Calliactis behaves as a closed animal in its movements, although its stomodaeum appears to be widely open to the exterior.

Observations of the movements of the animal are correlated with variations of the internal pressure. It is shown that expansion is not merely ‘passive relaxation’, but is generally accompanied by a rise in pressure which is, however, much lower than that which accompanies rapid closing.

It is concluded that the fluid-muscle system of Calliactis behaves in a similar way to that of other soft-bodied invertebrates, but that the system works at a much lower pressure.

A brief résumé is given of the work done on British Folliculinidae up to the present time.

Descriptions follow of eight British species, many of which are revised accounts based on personal observations.

A new species, Folliculinopsis elongata, is described.

A revised key for the identification of British Folliculinidae is given.

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 comparison of photographs taken on the eastern shore of Salcombe harbour before and after the disappearance of much of the Zostera marina L. shows that where previously there existed extensive sand banks, stabilized by the growth of this plant, there has been a lowering of ground level of 2 ft. or more, due to the washing away of the sand where the Zostera has died. Much of the ground is more stony than before and has become largely covered with seaweed attached to the stones. The buried fauna is not as rich as it was and some species previously common are rare or have disappeared altogether. A few small patches of Zostera still survive, but the plants are shorter with narrower leaves than before.

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.