Stichococcus bacillaris has been grown under conditions of varying ionic concentrations. Sodium chloride appears to be the dominant compound in determining growth of this euryhaline alga and from the reaction to increased sodium chloride concentration it is postulated that S. bacillaris is a freshwater organism which can tolerate high salinities. Some morphogenetic effects of high salinity are described.

Evidence for the presence of silica in the costae of Stephanoeca diplocostata Ellis has been provided by a combination of light and electron microscopy. The solubility of costae in hydrofluoric acid has been demonstrated. The presence of silicon in the costae has been strongly confirmed by means of the X-ray analytical electron microscope (EMMA) but tests for a crystalline substructure by means of electron diffraction were negative; it is concluded that silicon is present in a crystallographically amorphous form. Preliminary observations on other biological aspects of the organism include the presence of a sac-like membrane between the lorica and protoplast, the presence of immature costal strips within the cytoplasm and the nature of ingested food. The phyletic position of the group is briefly discussed with special reference to mitochondrial substructure.

The preliminary check-list of British marine diatoms first appeared in this Journal about 20 years ago (Hendey, 1954), and since that time many advances have been made in the study of these organisms. First, the known flora has been extended very considerably (Hendey, 1964, 1973) and much has been added to our knowledge of the structure of the valve by the use of the scanning electron microscope through the work of Hasle (1964, 1965a, b, 1972) and that of Ross & Sims (1970, 1971). This new information must inevitably lead to a reappraisal of views held on phylogeny within the group and consequently upon its systematic classification. While it would be premature at this stage to over-emphasize the importance of information gained in this way until a wider range of species has been examined, sufficient exists to support some minor changes and prepares the way for more radical changes that the new developments suggest. It should be pointed out, of course, that most of the ‘new information’ should more correctly be interpreted as confirmation of earlier views based solely on structure as seen in the light microscope of classical design and that some of the changes made in the classification as a result of these had been made many years previously, but the scanning electron microscope has enabled us to see more clearly the ultimate structure of the siliceous frustule of the diatom, thus permitting more positive decisions to be made regarding relationships and possible lines of descent.

At the First Symposium on Recent and Fossil Marine Diatoms held at Bremerhaven in 1970, Simonsen (1972) put forward some ideas for a more natural system of classification of the centric diatoms.

The thin-walled setae on the outer rami of the antennules of decapod Crustacea are considered to be chemoreceptors. It is not known whether stimulatory molecules enter each seta through the cuticular wall or via an apical pore. In this paper evidence is presented that the antennular chemoreceptors of the brown shrimp, Crangon crangon (L.), bear apical pores. In some field and laboratory populations, however, the pores are blocked by an epizooic, blue-green alga and this provides a direct means of testing the hypothesis that the apical pore is important in the sensory process.

The larvae of both Cardium edule, Linné, and Cardium glaucum, Bruguière, have been reared to metamorphosis under laboratory conditions.

Successful artificial fertilization has been shown possible, in both species, in the termperature range 10 to 20 °C. The larvae of C. edule show poor growth at 10 °C, good growth between 15 and 20 °C and erratic growth at 30 °C. C. glaucum larvae show negligible growth at 10 °C, but are able to grow well between 15 and 31 °C; limited numbers of larvae were reared to metamorphosis at 33 °C.

The optimal salinity for rearing the larvae of both cockle species was found to be between 30 and 35 ‰. Although C. glaucum larvae were slightly more tolerant of salinity extremes, both species were able to withstand a wider range of salinities than those satisfactory for growth.

Studies were made relating to the problem of how Calanus feeds during winter in the Clyde sea-area. Different diets were assessed in terms of sustaining the levels of body nitrogen and phosphorus in Calanus helgolandicus (Claus) over a period of several days. The test diets, all equivalent to the same level of particulate nitrogen in sea water, were: (1) suspended matter collected from the Clyde sea-area in winter; (2) particulate material produced in a foam-tower by bubbling sea water enriched with soluble extracts of plant cells; (3) living nauplii of the barnacle Elminius modestus Darwin; (4) dead nauplii of this species.

It was found that neither body nitrogen nor body phosphorus was sustained by diet 1; that body nitrogen, but not body phosphorus, was sustained by diet 2; that both were sustained by either of diets 3 and 4.

With living Elminius nauplii as the food, each Calanus captured the equivalent of 25 % of its body nitrogen and 47·3 % of its body phosphorus daily: with dead nauplii as the food the corresponding values were 34·4 and 44·5%. These rations are much higher than those found in an earlier study of Calanus grazing on a spring diatom increase in the Clyde (Butler, Corner & Marshall, 1970) and demonstrate that animal diets are readily captured.

In general, the results indicate that Calanus could survive the winter in the Clyde sea-area by feeding carnivorously.

Pilchard eggs were collected over a grid of 30 stations visited on 14 cruises from August 1969 to November 1970. The samples were taken with oblique tows of a 1 m terylene net at 4 knots, the average volume of water filtered being 750 m3. The formalin preserved eggs were graded into the series of stages described by Gamulin & Hure. No very early eggs were found, but from the occurrence of stage 2 eggs it is deduced that most spawning takes place in the early hours of darkness, between 20.00 and 24.00 h B.S.T.: some spawning must also occur all round the clock.

There were two main peaks of spawning, June-July and October-November, when large numbers of eggs were found inshore; the average numbers reached 196 per m2 water column in July and 30 per m2 water column in October. Smaller numbers of eggs were taken in the other months of the year, mostly offshore, and with a minimum in December–February. In the spring (March-May) the area sampled was well clear of the main area of spawning of pilchard in the approaches to the Channel, north or northwest of Ushant.

During the peak months no particular part of the sampling area appeared to be especially favoured for spawning.

The significance of the two main peaks of spawning is discussed in relation to the problem of recruitment of fish to the population. As an alternative to the accepted hypothesis that young pilchard move back to the Bay of Biscay for maturation it is suggested that some of them, at least, may survive and mature in the Channel.

A range of 62 species of marine fishes representing 34 families was examined for the presence of parasitic copepods. Forty-one species were found to harbour 39 species of copepod belonging to 9 families. The remaining 21 species of fishes were not infected. The incidence and intensity of infection were recorded and these provided material data on the host-parasite relationships. The site of infection and the developmental stage of the parasite were also recorded. The frequency distributions of number of copepods per host were calculated for Clavella adunca and Bomolochus confusus. The age of the host was shown to influence the frequency distribution of Bomolochus confusus. The host specificity of the copepod species was analysed and 70 % of the species were found to be specific for one host species or for different species of the same genus.

In this investigation of the wounds occurring on blue sharks, tooth cuts were found only on females over 180 cm long, supporting the view that they are courtship scars incurred during breeding. However, it seems unlikely that these sharks normally mate in British waters. It is suggested that tooth cuts can provide information on the size at sexual maturity of the blue shark in European seas.

Data collected over a period of 15 years for lobsters maintained at 10 °C and weighingfrom < 1·0 to 1200 g have been analysed. Equations have been produced defining the relationships of the cast shell weight, the growth increment at the moult, the inter-moult period and the food intake per moult with the weight of the lobster, and of the growth increment with the food intake. In particular, a growth curve has been derived showing the weight of lobsters, kept at 10 °C, with age. It is suggested that when there is an adequate food supply, the growth increment is a constant proportion of the lobster weight, and that variations in growth rate are achieved by changes in the length of the inter-moult period which, in turn, is mainly dependent upon the temperature of the environment.

The exceptionally heavy settlement of larvae in the autumn of 1970 made it imperative to continue the observations of the previous ten years. This two-year extension has yielded much new knowledge about the growth of Sabellaria colonies at Duckpool, and about other aspects of their life. It revealed that the more densely packed the young were the faster their colony grew, provided conditions were favourable. In unfavourable circumstances close packing of young delayed growth. The rapid elongation of young tubes surrounding older tubes sometimes resulted in holes and fissures forming when the older worms failed to maintain all-round contact with surrounding young as the surface area of a colony increased. Such holes and fissures gave a false appearance of physical damage, and in colonies where they formed weakened the whole structure, becoming a factor in its ultimate destruction by wave action. Such fast-growing colonies have shorter lives than others growing more slowly and remaining more compact.

Two new deep-sea barnacles (Cirripedia) are described. The first, from approximately 5200 m in the Southwest Atlantic, belongs to the most generalized genus of the order Ascothoracica, Synagoga. The two previously known species, S. mira from the Mediterranean and S. metacrinicola from Japan, are from relatively shallow water. The new species is not only more generalized than either of these, but it exceeds previous depth records for any ascothoracican by more than 1000 m. It is apparently a sequentially protandric hermaphroditic ectoparasite, knowledge of which helps clarify difficulties in interpreting the life histories of certain more highly evolved endoparasitic forms. On the other hand, its markedly generalized features bear heavily on considerations of the origin of the Maxillopoda.

The second new species, from approximately 1500 m in the Bay of Biscay, belongs to the most generalized genus of the order Acrothoracica, Weltneria. It is closely related to W. hessleri known from 1000 m off Bermuda and the two are unique in being the only true deep water members of the order. The new species is remarkable in inhabiting a friable, clayey substrate - all other acrothoracicins are known to burrow only in relatively solid forms of calcium carbonate. However, both have a calcified rostral plate, and this indicates that the Acrothoracica stem from scalpellid rather than cyprilepadid or iblid Lepadomorpha.

Measurements have been made, by neutron activation analysis, of arsenic, cadmium, antimony, mercury and zinc in organisms and bottom muds, mainly from Southampton Water and the Solent. The values are on a dry weight basis and refer to whole organism soft tissues unless otherwise stated.

Concentrations of mercury in algae ranged from 0·07 to 0·22 ppm and those in animal tissues from 0·06 to 1·9 ppm. The distribution of the element in various tissues of Mercenaria mercenaria was rather uniform, except that the concentration in the gills was about 2·5 times that in the whole organism. Variations amongst organisms from different parts of the Solent area and comparisons with other regions suggested some possible influences of local waste discharge, but there was no evidence of major effects. Anoxic muds contained higher concentrations of mercury than occurred in unreduced surface layers, suggesting mobility in interstitial waters of the uppermost zone and fixation under reducing conditions.

A high concentration of certain planktonic animals was found in a frontal region in the English Channel. Temperature, salinity and current measurements and direct visual observations (underwater) describe the nature of the front. It is shown that water depth, season, strong tidal mixing and residence time are important factors leading to the formation and maintenance of a turbulent convergent tidal front.

The distinguishing features of the common squid of British waters, Loligo forbesi, are summarized, and contrasted with those of L. vulgaris. The life-cycle and growth of L. forbesi are described, based on samples from trawl catches off Plymouth. This species seems to be an annual - young squid first appear in the trawl in late May, when their length is about 10 or 11 cm. Subsequent growth is rapid, and the males reach 30 cm and the females 25 cm by November. Spawning takes place mainly in December-January, but may continue into the spring. Neither sex survives beyond a single spawning season. Hatching of the spawn probably takes 30–40 days, and if the young squid taken in the trawl in late May hatched in the early part of the same year, a growth rate of about 25 mm/month would be required. Known growth rates for other species of Loligo are about 20 mm/month, so that indicated for L. forbesi does not seem to be impossibly high. The life-cycle is summarized in Fig. 8. There is also a summer spawning population, which grows to a rather smaller size at maturity, and which also seems to be annual.

During the summer L. forbesi ranges throughout the English Channel and southern North Sea, particularly in inshore areas. In October the squid migrate farther offshore and tend to occupy the western part of the Channel.

Values for total weight of squid/2 h trawl are given, on a monthly basis, for 1966–9. The largest quantities are usually taken in October and November, the highest single figure being 30.54 kg/2 h trawl, in November 1967.