Stafford (1913) rejected the view of many early workers (see Ryder, 1883, 1884; Huxley, 1883; Horst, 1886) that oyster larvae cemented themselves to the substratum with secretions of the mantle edge. He thought that the mantle margin could not be extended sufficiently to form the extensive area of cement that he found on the left valve of cemented larvae. Furthermore, he argued that the mantle could not secrete so much material in the short period that larvae took to cement. He deduced from the much reduced state of the ‘byssus gland’ in settled larvae that this gland was the source of the cement and suggested that the cement was spread over the shell by the foot. Nelson (1924), Prytherch (1934), Cole & Knight-Jones (1939) and Cranfield (19736, c) have clarified the role of the foot in cementing. Nelson (1924) also noted that cementing oyster larvae extended the mantle margin over the substratum but considered that this action spread the cement discharged by the foot and that the folds themselves did not secrete more material. The other authors, like Stafford, have dismissed or ignored any part the mantle folds might play in cementing.

Three deep-water species of the north-eastern Atlantic have been studied: Caryophyllia abyssorum Duncan, 1873, C. calveri Duncan, 1873, C. sarsiae n.sp. Of these only C. abyssorum has not been found in the Mediterranean. In the north-eastern Atlantic these species appear characteristic of somewhat different depths, but occasionally can be found together. Obtained by early deep-sea expeditions (“Porcupine” cruise of 1870, cruises of Prince Albert I of Monaco), all three species have been previously confused and assigned, chiefly, to the little-known fossil species C. arcuata and C. cylindracea. In order to show the world-wide confusion about C. arcuata, some other records, from Cape Verde Islands to Japan through Antarctica, are quoted.

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.

The life history and taxonomic position of Rhodymenia palmata (Linnaeus) Greville, one of the commonest red algae in the northern hemisphere, have been a source of considerable speculation. Carpogonial plants and carposporangial plants are unknown although tetrasporangial plants are common and spermatangial plants have been reported on numerous occasions. A parallel situation occurs in the genus Halosaccion Kützing for which carpogonial and carposporangial plants have never been recorded and spermatangial plants are well known only in the species Halosaccion ramentaceum (Linnaeus) J. G. Agardh. It is proposed in this paper to consider the relationship of Rhodymenia palmata to the other genera of the Rhodymeniaceae (Rhodymeniales) particularly Halosaccion and Leptosarca Gepp & Gepp.

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.

Muscle receptor organs (MRO) are present in the abdomen in a wide variety of higher Crustacea (see review by Alexandrowicz, 1967), though most experimental work on these organs has been carried out on representatives of only the Astacura and Palinura, in which the anatomy is relatively uniform. In the very varied group Anomura, they have been reported from among the Galatheidea, Thalassinidea and Paguridea (Alexandrowicz 1952b; Pilgrim, 1960); in the latter paper, they were shown to have properties physio-logically similar to those of the Astacura and Palinura, with slowly- and fast-adapting components. Stretch sensitive organs also occur in the thorax of many forms, but are of two distinct types there. In the posterior thorax are MRO comparable with those of the abdomen, i.e. comprising receptor cell, specialized muscle and a complex innervation of excitatory and inhibitory nerves as well as sensory fibres. In the more anterior thorax are the relatively very simple N-cells, whose dendrites spread among the fibres of non-specialized muscle and which are not known to possess any accessory innervation (Alexandrowicz, 1952a).

Heteromorphic life histories are now known for a number of species of Bryopsis, B. halymeniae Berth. (Hustede, 1964), B. monoica Funk (Rietema, 1971a), B. plumosa (Huds.) C.Ag. (Rietema, 1969, 1970) and B. hypnoides Lamour. (Rietema, 1971; Bartlett & South, 1973). Further it has been shown by Rietema (1970, 19716) that for both B. plumosa and B. hypnoides the life history changes with latitude.

The changes in the number of species, the number of individuals and the production of a benthic mud association have been studied for a 4-year period. The numbers of species and the total estimated production appear to have remained substantially stable, but the number of individuals has more than doubled over the period. When considering the high ranking producers, it is clear that not all of these have contributed to the general rise in numbers of individuals. Two species, Ammotrypane aulogaster and Abra nitida have shown an abrupt fall in population numbers and biomass. At the beginning of the investigation in 1971, these species figured importantly in the production estimates with 20 and 6% respectively of the total production. After 1971, both were effectively eliminated from the production of the association.

In many of the more general studies on marine zooplankton the part played by siphonophores is frequently ignored or only given a cursory mention. However, their ecological importance is far from insignificant. In this context we are indebted to the late Mr A. K. Totton whose publications have done much to draw attention to the siphonophores and the part which they play in the zooplankton community. His synopsis of the siphonophores (Totton, 1965) is a masterly work from which any student of this fascinating group can derive much benefit.

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.

Within the Chromophyta (sensu Christensen, 1962) a number of genera having benthic phases in which the vegetative cells are embedded in masses of thick, sometimes stratified mucilage, have been described from both marine and freshwater habitats. Examples include Gloeochrysis Pasch. (Pascher, 1925), Geochrysis Pasch. (Pascher, 1931), Sarcinochrysis Geitl. (Geitler, 1930), Chrysotila Anand (Anand, 1937) and Ruttnera Geitl. (Geitler, 1942). In many cases the vegetative stages are so similar morphologically as to be almost indistinguishable, especially in the juvenile condition in which the cells are often arranged in regular blocks (the ‘Sarcinochrysis’ condition) and under such circumstances it is difficult to ascertain their true systematic relationships.

Young Homarus vulgaris were reared in the laboratory up to stage V. All settled during stage IV by burrowing under stones placed on a sand or mud substrate. Half of the 100 animals studied burrowed within 6 days of reaching stage IV and did not subsequently vacate the burrow. The burrows were made with two openings on opposite sides of the stone which, in the case of the sand burrows, served as a roof. The burrows were made by the same methods as previously described for young and adult H. americanus

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.

Nine hundred and fifty-four bass were tagged, mainly by anglers, in the river estuaries and off the coasts of Cornwall, Devonshire, Dorset and Hampshire, England, in 1970 and 1971. To date 59 bass have been recaptured, 86 % by anglers, 12 % by commercial fishermen and 2 % by research vessels. Forty-seven bass were recaptured within 16 km of their release point. Of the 12 bass recaptured at a greater distance, four were taken within 90 days and had moved by an average of 1.4 km/day. From the tag returns and the length distributions of the bass tagged by areas it is concluded that bass form permanent populations in estuaries until they are 2–3 years old, when they move offshore, eventually becoming very mobile as evidenced by the long-distance movements observed.

Moult increments, annual moult frequency and hence annual growth were determined from suture-tagged edible crabs (Cancer pagurus L.) released and recaptured off Devon, Cornwall, and Dorset.

The average moult increments of males and females at a premoult carapace width of 100 mm were similar; at larger sizes the average moult increment of females was considerably less than that of males. Annual moult frequency of C. pagurus in south-west England decreased with increase in size, females more so than males.

As a result of the smaller moult increments and lower moult frequency of females, their annual growth is considerably less than that of males. This appears to be the result of three aspects of sex and reproduction: (1) reduction in moult increments, probably as a result of competition for nutritive resources between egg production and body growth; (2) the interruption of the moulting cycle by successive annual spawnings from a single impregnation at the previous moult; and (3) accentuation of the larger increments in weight at moulting of male crabs due to the allometric growth of their chelae. A consequence of the higher growth rate of males is the presence of very large male crabs – a distinctive feature of the population structure of the stock off south-west England.

The growth of C. pagurus in south-west England was compared with published data for stocks off the east and north-east coast. Moult increments were similar for both areas, but there were considerable differences in the moult frequencies. In the south-west, males moult more frequently than females; the opposite is the case for the east and north-east crab stocks. A valid reason for this difference has not yet been established.

In 1930, Colman (1933) made a study of the zonation of common intertidal animals and plants on Blackstone or Church Reef, Wembury. Four lines were marked out across the reef, and three of these, which radiated from his so-called ‘Central Rock’, were resurveyed during the summer and autumn of 1973. Besides the authors, help was given in the 1973 survey by Mr P. G. Corbin, Dr P. E. Gibbs, Dr P. K. Probert, Dr A. J. Southward, Mr R. L. Barrett and Mr T. J. Perry. Mr G. A. W. Battin was responsible for surveying and levelling, and Mr D. Nicholson for the photography.

Chemostats were used to study the relation between growth rate, the rate of nutrient uptake and internal and external nutrient concentrations of two nutrients simultaneously. (Monochrysis lutheri: phosphorus and vitamin B12.)

Growth rate and internal concentrations of both limiting and excess nutrients are related by simple rectangular hyperbolas.

Control was shown to follow a threshold rather than multiplicative pattern; that is, non-limiting nutrients exert no control at all over the pattern of growth. The limiting nutrient was the one that showed the smallest cell quota: subsistence quota ratio.

Monochrysis populations exhibited two modes of growth. ‘Slow adapted cells’ differed from ‘fast adapted cells’ in the values of the constants for the above relation.

Uptake of both limiting and non-limiting nutrients was found to be controlled by internal as well as external substrate concentrations. There was thus a limit to luxury consumption of one nutrient when growth was limited by another.

The mathematical model formulated for growth in a chemostat (equations (23)–(29)) allowed prediction of external and internal substrate concentrations and rates of uptake of two nutrients and of biomass, given only the input concentrations of the two nutrients and the dilution rate. This model should apply equally well to growth in batch cultures; its possible application to natural populations was discussed.

The turbot Scophthalmus maximus L. is a large teleost flatfish of the family Bothidae. Its range extends from the Adriatic (Faber, 1883) and Mediterranean (Morgan, 1956) northwards to the Norwegian coast, and includes the Baltic Sea and waters surrounding the British Isles. It has been recorded as far north as the Lofoten Islands (Fulton, 1905), and is taken occasionally at Faroe, Iceland and Rockall.

The use of diversity and evenness indices is well established in recent ecological literature. Many indices have been proposed, to such an extent that the choice of a suitable index became somewhat of a problem. Recently, however, Hill (1973) introduced a unifying notation where diversity numbers are denned in relation to Rényi's definition of a generalized entropy. Hill showed that his diversity numbers Na of the oth, 1st and 2nd order coincide with three important diversity measures which have been frequently used, No = S, N1 = eH and N2 = 1/SI, where S is the number of species, H is the shannon-Wiener information function –Σpi In pi and SI is Simpson's index . According to this notation, evenness should be calculated by dividing two of Hill's diversity numbers, e.g. N2/N1 = eH/S. This index was proposed by Sheldon (1969), but its use in ecological literature has been negligible. The most commonly used evenness index has been the one proposed by Pielou (1966), e = H/Hmax, with Hmax = lnS. Contrary to Hill's (1973) statement, it shares with Hill's continuum of evenness measures the property of remaining constant when the number of individuals of all species is multiplied with a constant factor. Intuitively, this seems to be a necessary property of an evenness index.

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.