1. The observations were made on the Hunterston Sands, Ayrshire, opposite the Cumbrae.

2. Small cockles appear on the ground about the beginning of August. This points to the breeding season being in summer and not spring, as is usually stated.

3. By the end of the first autumn some few of the spat are as much as 10 mm. in length, but most are under 6 mm. The winter ring is faint and easily overlooked.

4. The first of the several well-defined rings is therefore not the first but the second winter ring.

During the year 1928 the writer was engaged in a study of the bionomics of the oyster drills on the oyster beds in the region of the River Blackwater, Essex. At this time the presence of a foreign species was detected (1) and definite records were made of the relative abundance of the three following drills or tingles:—Murex erinaceus (=Ocinebra), Purpura lapillus (=Nucella), and Urosalpinx cinerea. It so happened that the winter of 1928–29 was unusually cold; the temperature of the water over the oyster beds was unusually low in January and February, 1929, ranging about the freezing-point of fresh water (see Table II and Fig. 1). The oyster-cultivators in this locality had many years previously stated that during severe winters many marine animals, such as the oyster drills or tingles and the burr Echinus miliaris, are killed in such great numbers as sometimes to exterminate the species. The observations made by the writer in 1928 offered an opportunity to test these statements, and of estimating the effect of the extreme cold in early 1929 on the animals mentioned above.

Illustrations are given of successive stages of the gonadial products, of the European oyster (O. edulis) after the act of egg-spawning. Both, microscopic and fresh preparations are figured.

A Preliminary survey of the area with regard to the distribution of the total nitrogen and phosphate content of the muds was described in a previous paper (Moore, 5). A number of stations were worked, and these were further examined for nature and distribution of particles, water content, and density, and as a result of this survey certain stations were chosen as suitable for more extensive work. At the same time it became evident that the layers in which the greatest and most important changes were taking place were those within a few centimetres of the surface, and these were therefore studied most intensively.

In fine muds such as those covering most of the bottom in the deeper parts of the Clyde Sea Area the formation of fæcal pellets is a factor of great biological importance. In these muds up to 40 per cent of the fine material is often consolidated into fæcal masses, and in extreme cases even the whole of the mud may be in the form of pellets. The significance of this process is clear. In the first place, the effective particle size of a large proportion of the mud is very greatly increased, and this in turn affects such characters as the porosity of the bottom, and the liability of the material to be transported by currents. In the second place, among selective feeders such as Syndosmya alba, which feed on the mud, there is an economy of labour, in that food which has once passed through the gut is set aside in a form in which it will be refused if again taken in by the siphons. This latter process can readily be seen in the example cited whose rejecta on examination prove to be almost entirely composed of pellets of its own and other species.

In carrying out detailed investigations into the life-histories and distribution of the Rays and Skates around the extreme south-west of England, large numbers of commercial landings have had to be examined. On account of their size and cost, regular and adequate samples of Rays and Skates cannot be delivered at the laboratory, as is possible with such a small and inexpensive fish as the Herring, for example. It therefore has been essential to learn rapidly to distinguish the different species as they lie exposed for sale on the fishmarkets. This has been necessary not only to promote rapidity of work, but also to obviate all unnecessary handling of the fish, too much interference with which is apt greatly to annoy fishermen, salesmen, and buyers alike.

As a serpulid, Pomatoceros triqueter L. realises to the highest degree the adaptation to a sedentary life. The calcareous tube in which this annelid lives is characterised by a keel running along its upper surface. It is rather misleading to say that this tube is triangular in section. Figure 2 shows a newly formed calcareous rod; it is spur-shaped; the two rami of the spur might approach each other so nearly as to simulate an almost complete tube. The substratum in this species not only serves as a support, but completes the tube. This is in accordance with the fact that the tubes of Pomatoceros never extend freely off the support as happens with tubes of other serpulids–Protula, for instance. The aim of this paper is to record some observations on the way an adult Pomatoceros endeavours to build a new calcareous tube if it is artificially removed from its old one. I undertook this observation as original work at Roscoff, where a complete literature was not available. I discovered later that Harms, in the course of his research on regeneration in Hydroides pectinata, arrived at identical results. My paper cannot therefore pretend to more than a confirmation of previous results.

In a previous paper (Lebour, 1930) the general characters of the larvæ of Galathea were described and the various stages of Galathea strigosa and Galathea dispersa identified. The present paper deals with the larvæ of Galathea squamifera and Galathea intermedia which have also been followed through their life histories. This completes the larvæ of the Galatheidæ from Plymouth with the exception of Galathea nexa, the larvæ of which have not been seen. As is noted in the previous paper this Galathea is regarded as a separate species from G. dispersa.

1. The diurnal behaviour of Sagitta of different sizes is shown as a result of collections made with the 2-metre stramin ring-trawl throughout 24 hours on July 15th–16th, 1924, and on June 3rd–4th, 1926.

2. The younger stages of Sagitta elegans appear to withstand higher intensities of light in the daytime than do the older stages, and they migrate first to the surface at dusk, as do those of Sagitta setosa. The older stages leave the surface first at dawn.

3. Diagrams are given showing the curves of equal intensities of light beneath the sea surface throughout 24 hours as calculated from air intensities obtained in June, with a reflection loss of 15%; (a) assuming a coefficient of absorption of 0·200 at all depths, and (b) assuming a coefficient of absorption of 0·100 at all depths.

4. It appears, from a comparison of the behaviour of Sagitta elegans with the calculated light conditions beneath the surface, that the older Sagitta at any rate are more sensitive to light in the early morning after the darkness of the night and can become adapted to light of higher intensities later in the day.

5. Previously published observations on the behaviour of Sagitta sp. on June 17th–18th–19th, 1925, show quite a different type of behaviour from the above, possibly due to more transparent water, the Sagitta only appearing abundantly above 30 metres in the dark. They had again migrated to below 30 m. before there was any appreciable light.

In recent years attention has been given to the influence of electrical currents as fish deflectors or screens, and experiments have been made to determine the magnitude of the currents which are sufficient to paralyse or act as deterrents to fish which may enter the electrical field, but in such strong fields the perception of the mechanism by which fish respond to electric currents is masked by the paralysis produced. It seemed possible that experiments with very weak currents might give fuller information concerning the mechanism by which fish respond to electrical stimulus than those made in strong fields. There is also the possibility that weak electric currents may occur in nature to which fish respond, but before exploring that field of phenomena it is necessary to observe the behaviour of fish under the influence of very weak fields. McMillan found that the field (volts per inch) required to paralyse young salmon varied with the resistivity of the water; thus when the latter was 10,000 ohms per inch cube the paralysing voltage was about 1·5, so that a current density of ampere per square inch was sufficient to cause paralysis, whereas when the resistivity was twelve ohms per inch cube the current required was ·03 ampere. In the former case the conductivity of the fish was greater than that of the water, in the latter case less.

1. Among schooling fish, the younger stages of the bass (Morone labrax) provide an instance in which the schooling habit, though strong, is not stereotyped into fixed forms of behaviour.

2. Observations were made on individual fish in connection with their attraction for one another, a special point being made of observing their behaviour in front of a mirror.

3. The data so obtained are summarised in the light of their bearing on the problems of school formation.

In both the series of hauls made for the purpose of estimating the reliability of a single haul of the International Vertical Net, the possibility that the variation in the size of catch of successive hauls is due to errors of the methodique has been examined.

Errors due to variations in the speed of hauling, and to the effect of light and darkness on the catch of the net can be ruled out.

The enumeration error, even where the enumerated total rests on a single count, is insufficient to account for the major part of the variations found, and, having regard to the fact that such totals were derived from two, and sometimes more, separate “counts” from each sample, there is good reason to believe that the main cause of variation in the size of catch is to be sought elsewhere, the most likely being the lack of uniformity in the distribution of the organisms themselves.

(1) Cotton and linen fabrics were exposed horizontally on the Laboratory roof at Plymouth for two years. During this time the fabrics lost from one to two-thirds of their initial tensile strengths in both warp and weft.

(2) The application of copper oleate, mixed copper soaps, also of the latter with resin or tar as binding agents, had no effect or a slight effect only in lessening deterioration; such weakening must therefore be due to weathering, chiefly the action of light, since these substances have been shown to be useful antiseptics on nets immersed in salt or fresh water.

(3) No deleterious action may be expected when nets treated with these substances are exposed to light, since the treated fabrics were no weaker than the untreated; but where Cuprinol had been used, there appears to have been some weakening, though the antiseptic properties of Cuprinol are excellent.

Somewhere about 1914 D. J. Matthews maintained the sea-water in the Plymouth aquarium tanks at a pH value close to that of the outside sea-water by the addition of suitable quantities of sodium carbonate.

1. It is not always feasible to determine pH on board ship, owing to bad light and other conditions, although it may be possible to collect water samples.

2. By preserving the water samples on collection with mercuric chloride solution (four drops per 100 c.c. of water) and by taking care to leave only a small air-space in the bottles it is possible to keep the water practically unchanged for many days.

3. Test tubes containing such water (10 c.c.) plus 0·02% cresol red (0·5 c.c.) have been-kept unchanged for three weeks at 12–14° C. and for two days at 33° C, whereas unpreserved water showed a drop in pH of 0·05 unit in one day at 12° C.

4. McClendon buffer solutions may also be preserved by mercuric chloride, but in this case a small correction must be applied since complex formation leads to a removal of effective buffer salts from the solution and a small decrease in pH.

In the examination of a total of about twenty-four thousand mussels from various localities in Devon and Cornwall—estuaries of the Fal, Hamoaze, Yealm, Teign and Camel, and the Promenade Pier, Plymouth— it has been observed that those from various parts of the Fal Estuary included a high percentage of specimens with the gills in an abnormal condition, whereas such abnormalities were rare or absent in other localities.

In view of Pelseneer's work on “Les Variations et leur Hérédité chez les Mollusques,” it seems worth while to record briefly certain observed abnormalities of the labial palps and the foot of Mytilus edulis. Among some thousands of specimens examined, however, such conditions were rare, and it is probable that at least some of them arose through injury.

Experiments have shown that the gill of Mytilus is capable of regeneration, and that this may occur in less than eight months. It may be confined to the formation of a food grove at the cut edge of the gill, without appreciable regeneration in length of the gill filaments. Regeneration of a food groove appears always to occur at the cut edge, if the ends of the descending and ascending filaments are able to touch and so to fuse. On the other hand, regeneration of gill filaments does not seem to occur invariably, and when it does the rate is slow, at least under experimental conditions and in mussels of a length of about 7·0 to 8·0 cm., such as were used for the experiments: it is possible that regeneration would occur more surely and rapidly in young mussels, but owing to the thinness of the shell they would be more difficult to wedge open without fracturing. Coulthard (6, p. 136), however, says that “The rate of growth is independent of size in the mussel, being apparently influenced only by the environment.” Perhaps the lack of an abundant food supply under the conditions of the experiments should be taken into consideration, though it is well known that in general the amount of food available to an animal has little influence on regeneration (9, p. 27). The salinity of the water in general circulation is about 36–37°/oo, that is, higher than normal sea-water, which is about 35°/oo, and would be considerably higher than the optimum salinity for growth (see Flattely and Walton, 7, p. 81). This may also possibly have a retarding effect on the initiation of regeneration and the rate.

Bulla hydatis is a mollusc of relatively rare occurrence in the Plymouth district, although fairly common across the Channel at Roscoff. Intermittent dredging and collecting in the Salcombe estuary over a period of about five years, and some rearing experiments carried out in the department of zoology, University College, London, have afforded some insight into its apparently peculiar distribution and also a few facts of certain general interest.

During the researches on the vertical distribution of plankton and on the-seasonal abundance of young fish, a record was kept of all Cyanea lamarcki Péron and Lesueur occurring in the catches of the 2-metre stramin ring-trawl. This was primarily for correlation with the abundance of such fish as the young whiting, Gadus merlangus, which at certain stages in. their development shelter under the umbrella of the medusa. Since it is only with the larger Cyanea that this association of the young whiting exists it was necessary to keep a record of the sizes of the Cyanea occurring in the catches. These were only rough measurements and denote the diameter of the flattened disc of the medusa usually to the nearest half-inch.