The Saltash tuck-net is used in the estuaries of the Tamar and Lynher for seine netting on soft mud. The fishery is carried on during autumn and winter, from open boats with crews of two men.

Hauls were made with a tuck-net in every month between November 1935 and December 1937.

The fish population of the estuaries is essentially marine: its composition changes from month to month with the arrival from, or departure to, the sea of different species of fish. With the exceptions of salmon (Salmo salar), sea trout (Salmo trutta) and some of the Gobiidae, all the fishes of the estuaries go down to the sea to spawn.

Buoys differ from the intertidal area in that they are constantly immersed near the surface of the water and the slope and texture of their surface is constant. The horizontal and vertical distribution of the macrofauna and macroflora on a series of buoys stretching from the open sea up the Tamar estuary is given.

There are differences in estuarine penetration even among species belonging to the same genus. Distribution is likely to be affected by the time of laying the buoys and the period in the water. But the six buoys farthest from the sea were laid down and lifted at approximately the same time. For these, at least thirty species were available for colonization, but little more than half that number was found even on the most seaward; and the number decreased up-river.

Light-adapted mysids as exemplified by Hemimysis lamornae display phototelotaxis which regularly alternates in sign from positive to negative and vice versa. This reaction may be disturbed by other activities such as feeding; it only takes place in horizontal illumination.

Dark-adapted mysids display negative geotaxis. When a light stimulus is given this geotaxis is reversed in sign irrespective of the direction of the incident light.

When the statocysts of the mysids are removed their responses are much more like those of planktonic creatures. In the light normal orientation is maintained by the “dorsal light reflex”, and in darkness by the “general position reflex”. In the darkness a feeble negative geotaxis is sometimes seen. In light, phototaxis is seen in both light-adapted and dark-adapted conditions; in the majority of cases it is negative but on occasion has been seen to be positive.

In 1932 crosses were made at Plymouth between Psammechinus miliaris ♀, both Z-type (from the shore) and S-type (from Eddystone), and Echinus esculentus ♂. The larvae from the S eggs differed in size and shape from those from the Z eggs (cf. Figs. 1,2 with 3–6). None of the hybrid plutei possessed the green pigment of P. miliaris, nor the posterior epaulettes of E. esculentus. Some of the larvae (Figs. 3, 4) had a posterior pedicellaria, like E. esculentus, in others this organ was missing (Figs. 1, 2, 5, 6). Some of these plutei were preserved, others went through metamorphosis. Healthy larvae of these combinations (00+ and 000) have not hitherto been described. The results are compared with those of previous authors (see table, p. 100). Some possible causes of change of inheritance in different years are discussed.

A method is described for obtaining growths of phytoplankton in samples of crude sea water, similar in composition but several hundred times more dense than phytoplankton communities occurring in the sea.

The ratio of nitrogen to phosphorus utilized by such communities has been determined.

They use ammonium in preference to nitrate, although the latter may be many times more concentrated than the former.

They use urea and uric acid as sources of nitrogen.

Certain amino-acids when added as sources of nitrogen were attacked by the bacteria in the community and either the ammonium set free or both the ammonium and the amino-acid were used by the phytoplankton. Others, as d-leucine, were not utilized, or, as l-leucine, only slowly utilized.

Sodium nucleinate and caseinate were rapidly broken down when added to crude sea water by bacterial action, and the phosphate produced utilized by phytoplankton. There was no significant utilization of glycerophosphate.

The amount of iron and phosphorus in Sagitta setosa and S. elegans has been estimated. As the winter population decreased in numbers the iron content per animal also decreased, rising again in what may have been the next brood.

This paper gives an account of a survey of the invertebrate populations (omitting Protozoa) of eight species of seaweeds on Church Reef, Wembury Bay, extending over the entire intertidal range.

Above high-water neaps the faunas are poor, except for that in Lichina pygmaea which is the richest in individuals on the shore.

Between high-water neaps and low-water springs the most numerous groups are copepods, acarines, young littorinids and (in Ascophyllum only) ostracods.

In the holdfasts of Laminaria digitata polychaetes are very abundant and make up the majority of the population.

The intertidal faunas are compared with those in the soil on land, and prove to be far more abundant. Even the most plentiful group in the soil, the insects, is rarely as numerous as it is in Ascophyllum around mean sea-level.

Altogether 177 species are recorded, of which 35 are not in the Plymouth Marine Fauna (1931).

Ten stations, from high water to low water, were investigated along a mud-flat in the Bristol Channel.

The mud was analysed for water content and grade. The values suggested, with other observations, that the stations were distributed over two different areas.

Quantitative analysis of both macrofauna and microfauna revealed a dense mud population.

The operative ecological factors, including the food cycle, are defined.

It has long been presumed that the gametes of certain Foraminifera are flagellated; however, the lack of conclusive evidence as to the origin and fate of these flagellated gametes has made their existence problematical.

In syzygous species of Discorbis the gametes are flagellated and the genetic relationship of these gametes is easily demonstrated, since gametogenesis, fertilization, and the development of two- and three-chambered multinucleate microspheric agamonts takes place within the excavated tests of two or more mononucleate megalospheric gamonts associated in syzygy.

The life cycle of Discorbis herein described is in general agreement with the life cycle of Polystomella crispa proposed by J. J. Lister, and completes an interesting series of life cycles in which a progressive modification in behaviour and test morphology can be traced.

Behaviour, ecology, and distribution of four syzygous species of Discorbis are discussed.

Multiple tests of these syzygous species of Foraminifera can be found in most rock-bottomed tide pools that supports a growth of coralline algae. These sexual groups provide a sure source of material for the demonstration of flagellated gametes in the Foraminifera.

The survey, the results of which are described in this paper, was primarily intended to investigate the zonation of Littorina littorea, but notes have also been included of the zonation of such other gastropod species as occurred with it. The material was collected from the following localities: Torpoint. 2. ×. 36. Just west of the ballast dock at Torpoint, Cornwall. The shore consists of stones, many of them bedded in mud, and thickly overgrown with fucoids. There is little wave-action, but at times a considerable drop in salinity (Hartley & Spooner, 1938; Mime, 1938).

Little is known of the larvac of the Pandalidac as is shown by Gurney (1939) in his Bibliography of the Larvae of Decapod Crustacea. Berkeley (1930,1938) describes the life histories of several species of Pandalus and of Pandalopsis dtspar from British Columbia, and Gurney (1937) the larvae and post-larvae of Chlorotocella, but beyond these the information is fragmentary. Sars’ (1900) work on Pandalus borealis and P. bonnieri was formerly regarded as typical of pandalid larvae but these were proved to be Caridion (Lebour, 1930). Sars (1900), however, described in part in an excellent manner the larvae of Pandalus montagui and Pandalina brevirostris and Stephensen (1935) the early larvae of Pandalus propinquus.

The life history of Sacculina carcini parasitic on Carcinus maenas in the Clyde sea area is discussed and the breeding period and the time of the emergence of the young externa are indicated. The time and duration of the breeding season are compared both with what has been found at Plymouth and Roscoff for the same species of parasite on the same host crab, and also with what was found by Day (1935) who worked in the Mersey area on Sacculina carcini but parasitizing Portunus holsatus.

The length of life of the Sacculina externa and their ultimate fate are discussed. It is shown that in male crabs which act as hosts the liability of the secondary sexual characters to modification is correlated with size.

In a number of previous reports observations on the seasonal abundance of the pelagic young of teleostean fish in the plankton off Plymouth have been recorded for the years 1924 to 1938 inclusive. Owing to the outbreak of war the series for the year 1939 is unfortunately not complete. Collections were, however, made until the last week in August. Previous records have always shown that the numbers of young fish caught in the last four months of the year, September to December, are insignificant and in consequence it is desirable that the results for 1939 should be published since they cover fully the period of production of almost all species of fish. It is, also, essential that these records should not be lost as the year 1939 has been the worst yet recorded and sets a new low limit to the production of fish. It is much to be deplored that the sequence of observations may be broken, so that we may never know what point the trough of the decline may reach.

Preliminary observations have been made in the English Channel off Plymouth on the average obliquity of illumination under water, and on the relative intensity of light reflected upwards at various depths, the readings being made with a cubical photometer containing six “Electrocell” selenium rectifier cells mounted behind opal glasses and Jena VG 9 (green) filters. The cells measured the light of wave-lengths about 480–580 mμ falling on upward-and on downward-turned horizontal surfaces, and on four vertical surfaces i n rectangular azimuths.

The average angle with the vertical or of obliquity was from 36 to 40°, and no significant difference could be detected between that for smooth sea and overcast sky, and that for rough sea and either high or low sun. Figures for smooth sea and sunlight are more difficult to obtain, as in the absence of drift due to wind the photometer may rotate.

No decrease in average obliquity with depth was found, in some cases there was evidence of a slight increase. This is in accordance with our previous results, and accords well with the constancy of extinction coefficient so often found throughout a series. It is not, however, in agreement with the careful work of Johnson & Liljequist, so further determinations would seem to be desirable.

The percentage of the light which was scattered back so as to fall on a downward-turned surface varied from 5.5 for comparatively opaque water (extinction coefficient 0.20) inside Plymouth breakwater, to 2.1 for very clear water (extinction coefficient 0.076) some miles off at sea. The presence or absence of sunlight had little effect, values close to 3.0 being obtained with and without sun for water having a coefficient close to 0.110.

The macrofauna of the intertidal mud-flats of the River Tamar have been investigated. Quantitative samples were taken by sieving the mud through a o·8 mm. sieve. Traverses of series of stations were worked at successive intervals up the river, and the tidal level of each station ascertained.

The characteristic species which inhabit the mud-flats are listed and the data secured regarding (1) population density, (2) up-river penetration, and (3) vertical distribution, are summarized and related to previous information on these points.

While some species are more or less uniformly distributed intertidally, others show marked zonation, with maxima in one part or another of the intertidal zone. Marine species which penetrate into the estuary tend to show the same intertidal distribution as in marine habitats. All five of the more strictly estuarine species are concentrated in the upper tidal levels.

In considering the limiting factors which cause a decrease of population at lower tidal levels, emphasis is placed on the probable importance of the increase in strength of water currents towards low water.

A survey of the Fal Estuary Beds in February 1939 gave evidence that the stocks of oysters were only slightly better than in the slump period of 1926.

The failure of the beds to show the recovery expected in recent years is attributed largely to the absence of sufficient clean culch on the banks.

It is suggested that means be taken to scatter clean culch over the banks in June yearly to prevent further decline of the beds and assist in their more rapid recovery to a flourishing condition.

The American slipper limpet, Crepidula fornicate, was not found and appears to be unknown on the beds.

The work described in this paper is a contribution to the general problems of rearing the larvae, and growing the spat of the European flat oyster, Ostrea edulis L.

The specific aspect of the problem dealt with in detail is the place taken by minute motile organisms (naked dinoflagellates and other unicellular algae) in the food requirements of the developing veliger larvae.

Six such flagellate organisms, ranging in size from 1·5 to 7 μ in diameter, have been isolated from sea water, and are maintained in pure culture, under conditions described. Pending specific identification, these are denoted by letter-labels only. These organisms have been used, over a period of years, in feeding experiments with oyster larvae.

The resting spores of Ditylum are formed as a result of a peculiar kind of plasmolysis of the protoplast (Gross, 1939); they are small spherical bodies lying inside the old cell wall. Since one-half of the cell wall is only slipped over the other half it is likely that in the sea they might become separated and the resting spore proper would drop out of the shell. In a previous paper (Gross, 1937) it was stated that in old cultures a considerable number of resting spores could be found outside the parental shells, and when transferred into fresh culture medium they only expanded in volume. Since then more attention has been paid to such isolated resting spores and the formation of new cell walls has been frequently observed.

During resting spore formation Ditylum loses the cell sap and the volume of the resulting resting spore is one-third to one-twentieth of the cell volume.

Ditylum plasmolyses in 3·5–I.7% NaCl solutions, and in a few seconds the protoplast is reduced to the size and structure of a resting spore. In 0·5% NaCl there also occurs a considerable reduction in volume. The plasmolysed cells recover completely when removed into sea water. Rapid plasmolysis was also observed in isotonic and hypotonic dextrose and sucrose solutions and in solutions of CaCl2.