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.

This paper presents results of an ecological study towards high-tide level near the mouth of the Dovey estuary, carried out in 1925–6. The area was treated as an extension of the sea floor, the only comparable work at that time being submarine. Petersen (1918) showed that on the bed of shallow seas the fauna could be grouped into “animal communities”, whose constitution was determined by depth, distance from shore, shelter and salinity. Analysed with regard to distance from high-water mark, and degree of shelter, the fauna of this part of the estuary shows Petersen's Macoma community over most of the area, with a Corophium community at high tide in the more sheltered part. Davis (1925), in the North Sea, substituted “soil associations” as an alternative ecological unit, a certain grade of soil carrying its typical fauna wherever it might be found. The two groupings already found in the Dovey estuary clearly emerged as soil associations, after adoption of a reliable method for analysis of fine-grade soils. Up to the present, oceanographers have used sieves or elutriation for soil analysis. Up to the present, oceanographers have used sieves or elutriation for soil analysis. These methods are unsatisfactory for examinations of estuarine soils, with their large proportion of fine material.

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.

The advantage of using laboratory-reared animals in the elucidation of trematode life histories is now generally recognized (Palombi, 1938; Stunkard, 1938, etc.). Further researches seem to emphasize this point. No matter how carefully controls are examined and no matter how precise is the morphological comparison between cercaria, metacercaria and adult fluke, the fact that the intermediate and final hosts have been exposed to previous infection in the wild—particularly by closely related species of worms—immediately detracts from the value of the experiments.

The number of eggs produced by the herrings of the East Anglian shoals increases with the length of the fish at a rate equal to the 3·465 power of the length, and with the age of the fish to the 0·66 power of the age. This fecundity is compared with that found in other races of herrings.

The number of eggs produced is closely correlated with the mean weight of the ovary, and it is found that the weight of the ovary increases with length at a rate equal to the fourth power of the length, and that a slightly higher rate applies to the testis.

The weight of the gutted fish, however, increases in relation to the length at a much slower rate, namely, as the 2·3 power of the length in the males, and the 1·5 power of the length in the females.

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.

The genus Gammarus, instituted by Fabricius in 1775, has come to include a large number of species—so many and so varied, in fact, that the necessity for a revision of the genus is well recognized. An extensive examination of the taxonomic literature has inevitably led to the conclusion that several more or less well-defined groups of species can be recognized among the total assemblage, and that some of these at least should be separated off as distinct genera.

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.