Data are given on the abundance of post-larval stages of teleostean fish in half-hour oblique hauls with the 2-metre stramin ring-trawl taken at weekly intervals at a position two miles east of the Eddystone lighthouse during the years 1930 to 1934 inclusive.

The seasonal composition of the catches is considered and it is shown that there is a gradual change over from the young of northern species of fish to those of more southern species as the summer advances. The relation between the spawning times of closely related species appears usually to be a function of their geographic distribution.

The period of maximum abundance of post-larvæ of spring-spawning fish occurs at different times in different years and this difference may be as much as a month. An apparent correlation between the times of abundance of young whiting and the previous temperature of the water has been shown.

It has long been known that there is a considerable seal population on the North Cornwall coast. But precise information concerning the species present, the density of the population, and the positions of the rookeries has been almost entirely lacking. In order to obtain data on these points, a detailed survey of the North Cornwall coast was carried out during the fortnight August 7th-20th (1935) inclusive.

1. Experiments have been done to determine the oxygen utilisation by male, female and Stage V Calanus under different environmental conditions.

2. An initial fall in the respiration of adult Calanus was observed during the first few hours after capture. Stage V do not show this clearly. It is found more often in winter than in summer.

3. The lethal temperature varies from 24° C. in winter to 26° C. in summer. Stage V Calanus are more resistant to high temperatures than adults.

4. Respiration rises with increase of temperature from 0° C. to 20° C. The increase does not follow van't Hoff's law. The oxygen consumption of males and females is about the same, while that of Stage V is lower. Above 20° C. there is a harmful effect.

5. Within the limits studied (pH 7.4–pH 8.5) change in hydrogen-ion concentration has no effect on respiration.

6. Calanus are unaffected by an increase in the oxygen content of the water, but are sensitive to low oxygen tensions. Below a concentration of about 3 ml. per litre the respiration decreases. At concentrations between 1 and 2 ml. per litre they are killed. They are more resistant at 5° C. than at 15° C. and Stage V are more resistant than adults at both these temperatures.

7. Calanus can become acclimatised to salinities as low as 35–40% seawater (S=12‰–13.6‰), but their respiration is lowered at a salinity of 50%.

8. Light has a striking effect on Calanus. It may increase the respiration by 100% or more. This effect can be detected also in the sea, but not below 5 metres. Continuous exposure to light is harmful.

9. The bearing of these results on the distribution of Calanus is discussed.

10. From the amount of oxygen used in respiration, calculations of the food required are made and these are compared with the results given by Putter for Calanus and other copepods.

In July, 1935, a cruise was made in Col. E. T. Peel's yacht St. George to study the distribution of certain plankton animal indicators in the mouth of the English Channel.

Three bodies of water were clearly shown by their plankton content:

(1) water characterised by the presence of Sagitta elegans, Clione, Themisto graclipes, Euphausian larvæ, Stephanomia and Aglantha; (2) Biscay water, on this occasion characterised by Noctiluca and a paucity of zooplankton; and (3) Channel water characterised by the presence of Sagitta setosa and absence of other indicators.

It has been shown that the study of certain plankton animals should prove of help in understanding the hydrography of the Channel mouth region.

1. The nauplius stages of three species of Longipedia are described, and the segmentation and armature of the appendages of L. coronata are given in tabular form.

2. The main features in the external structure of the copepodite stages are summarised in a table.

3. Additional points of resemblance between the nauplii of Longipedia and the cirripedes are presented.

4. Notes are given on breeding and development under laboratory conditions ; there is no evidence of parthenogenesis.

5. Feeding in the copepodite stage of Longipedia is described.

6. A description is given of the hitherto unknown male form of L. scotti.

Studies are reported of the behaviour of stored sea-water with regard to oxygen, ammonia, and bacteria content in relation to the conditions of storage and to the effect of various filtration procedures.

When sea-water is sterilised by filtration and stored in the dark, the oxygen content remains constant or diminishes only by less than 0·07c.c. per litre in several hundred hours.

In non-sterile experiments there is always an oxygen consumption roughly parallel to a bacterial multiplication which begins very suddenly after collection of the water. These effects are greatest in “raw” water, less in paper-filtered water and least in water which is doubly filtered.

The peculiar and exacting environment of Tigriopus fulvus is discussed and a census of Tigriopus from a series of pools in the Isle of Man is given.

Experiments have been made determining the resistance of Tigriopus to desiccation and its revival in favourable circumstances.

The life history has been worked out, times taken in development noted, and the various stages compared and contrasted with those described by Guiglia.

Sex can be determined at the fourth copepodid stage. Females are normally fertilised as fifth copepodids, but the males are not functional until the adult stage. A single female may produce several egg sacs giving rise to living nauplii from a single fertilisation.

There is no evidence for parthenogenesis.

Samples of animal and plant plankton were added to sea water in glass vessels and the subsequent changes in the phosphate content of the water were followed.

The breakdown of the zooplankton was very rapid and more phosphate was set free than had originally been added as plankton. The balance was produced from dissolved organic phosphorus compounds in the water. The breakdown of phytoplankton showed a short time lag and only a part of the phosphorus added was set free as phosphate.

In work on the biology of Balanus balanoides, use has been made of the method of differentiating the successive year groups by the colour of their shells. The present paper describes the method of doing this, and gives a brief account of the infective penetrative algæ which cause the colouration. The first author (M.W.P.) is responsible for the algological observations, and the second (H.B.M.) for the zoological observations.

In 1933 an examination of Peringia ulvœ for larval trematodes was under-taken at Plymouth (Rothschild, 1936). No actual measurements were made at the time, but there appeared to be a relation between the species of trematode and the size of the individual infected snails. Thus the commonest species, Cercaria oocysta Lebour, 1907 (14% infection), and C. ubiquita Lebour, 1907 (4% infection), were found in 75% of the largest snails, while the rarer species, such as C. ephemera Lebour, 1907 (non Nitsch) (2% infection), and C. pirum Lebour, 1907 (0–1% infection), occurred most frequently in medium sized individuals.

Although to many organisms manganese is known to be of great importance (Berkeley, 1922; Brenchley, 1927; Hopkins, 1930) its part in the economy of the sea is unknown. Some attempts were therefore made in 1934 to estimate the manganese in marine plankton using the residues from the determinations of phosphorus (Cooper, 1934; Harvey et alia, 1935). The residues from the triplicate digests from each cruise were combined and concentrated from about 200 to 70 ml. The concentrates were then examined quantitatively for manganese by the periodate method of Willard and Greathouse as described by Yoe (1928). In all cases but one the concentration of manganese was less than could be detected with certainty (Table I). In the absence of confirmatory data the figure of 5γ per litre of the diatom catch of May 15th must be regarded as suspect and attributable to chance contamination. Thus in these catches at L4 (5 miles off shore) during the spring outburst in 1934 manganese amounted to less than three parts per million million parts of water filtered, equivalent to one-thousandth or less of the phosphorus content.

1. Sixty specimens of B. haineri, of five successive year groups, were obtained in December, 1933, and a further 33 preserved specimens taken in the winter of 1925 were examined.

2. The mean ages contained for successive year groups from the size distribution and from individuals settled on those of the preceding year, yielded results in good agreement with one another.

3. First-year individuals do not spawn. All older individuals had ripe genital products in the 1933 material, and early embryos in the 1925 material.

The salt-marsh under investigation is situated at Aberlady Bay on the south shore of the Firth of Forth, fifteen miles east of Edinburgh.

The marsh is small and occurs at the mouth of a stream. The character of the soil on the two banks differs, being on the one side muddy with permanent pools, and on the other sandy, so that the pools tend to drain dry. The vegetation of the pools is variable, some containing species of Zostera, Ulva, Enteromorpha and Vaucheria, others having only diatoms.

The following short descriptions of several of the eggs and larvæ of Plymouth prosobranchs, hitherto unknown or imperfectly known, are brought together, although many of them are not fully worked out. It is hoped in the near future to publish a general account of the British species with reference to all known forms, including those which have been specially described from Plymouth.

Some of those described below have not yet been identified, but it is thought that it is worth while noting them for the benefit of future workers, especially some striking forms, important in the plankton on account of their size. This is notably the case with the three larvæ probably belonging to the Turridæ.

(1) Adults of Audouinia tentaculata Montagu were induced to spawn in the laboratory; the eggs were fertilized and the larvæ reared to metamorphosis and early bottom stages for the first time.

(2) The larvæ are yolky and do not feed. They have a broad prototroch and telotroch and a broad neurotroch. The ciliation of the head is rather complex. There are no bristles. When about ten days old they metamorphose.

(3) During metamorphosis most of the cilia, except those of the neurotroch, disappear and their cells are absorbed internally.

(4) Bristles appear for the first time a few days after metamorphosis. After a while branchiæ appear, followed by what are apparently tentacular filaments situated on segments anterior to those on which they occur in the adult.

(5) Discussion centres on the position of the tentacular filaments and the first pair of branchial filaments in the young worm as compared with the adult. The segmentation of the anterior achaetigerous region also receives attention.

The young stages of the members of the family Eulimidæ are little known, the only reference to any species apparently being that of Loven (1844) who briefly notes and figures a veliger which he attributes to Eulima distorta (=Balcis devians). This has a very oblique shell and was probably a week or two old. A comparison of this figure with the apex of Balcis devians from Plymouth and its larvæ in the plankton makes one rather uncertain of its identity but shows that even in those early times it was known that a Eulima could remain some time in the plankton as a veliger.

1. The relation between the dry weight of the decalcified barnacle and its shell volume has been determined in its relation to age, season and tidal level, at Port Erin, with the following results: (a) In immature barnacles, tissue growth continues throughout the year, but is most rapid in the spring and autumn, (b) In mature barnacles which produce a considerable amount of larvæ there is a heavy drop in tissue weight during the summer period of high temperature, and another slighter drop during the winter, the latter being apparently associated with the presence of developing larvæ in the mantle cavity.

2. Gonad samples were examined seasonally. At low levels on the shore the barnacles mature in their first year. Above this level they do not commence to mature until over a year old. The sequence of changes in the gonads is described. A condition of senility is found in many of the largest high-water barnacles.

3. The naupliar content was estimated in relation to size and tidal level, counts of up to 13,000 larvæ per individual being obtained. The dry weight of a fully developed nauplius was determined to be 7·5×10-4 mgm.

The post-larval stages of the bass, Morone labrax (L.), have never been recorded from these waters. From time to time occasional specimens of young fish have been caught in the plankton which had been tentatively assigned to this species on account of their similarity to the drawing given by Raffaele (1888). Now that the post-larval stages of this species have been described and figured by Bertolini (1933, p. 310 and Plate XIX) the Plymouth specimens can be definitely identified as Morone labrax, and the instances of their occurrence put on record.

1. Vertical traverses down the shore were worked at four localities in the Isle of Man, with varying degrees of wave-exposure, for which factor a coefficient is given.

2. The upper limit of distribution is high water neaps in a sheltered place, and up to high water of extreme spring tides at greater waveexposure. The lower limit similarly drops with increasing exposure.

3. Barnacles are largest and most abundant in a wave-exposed locality. The effect of wave-exposure may be reproduced by a current.

4. In sheltered localities the optimum level for growth, mean size, etc., is at low water for newly settled barnacles, but moves progressively up to high water as they grow older. In a very exposed situation, however, the optimum is always at low water.

5. In an exposed situation the gonads mature in their first year below about half-tide level, and in their second year above this level. With decreased wave-exposure the age of maturation rises, especially at high water until in a very sheltered place few barnacles mature at all.