In recent years the external morphology of marine choanoflagellates has been the subject of close scrutiny. This is a result of the attention given to marine nanoplankton, of which choanoflagellates are a part, and the relative ease with which choanoflagellates with loricae of costal construction can be observed in shadowcast whole mounts with an electron microscope. However, detailed ultrastructural studies of choanoflagellate protoplasts have been limited to one freshwater species Codosiga botrytis (Ehr.) Saville-Kent (Petersen & Hansen, 1954; Fjerdingstad, 1961; Hibberd, 1975) and four marine species Salpingoeca pelagica Laval (Laval, 1971), Stephanoeca diplocostata Ellis (Leadbeater & Manton, 1974), Savillea micropora (Norris) Leadbeater (Leadbeater, 1974) and Codosiga gracilis James-Clark (Leadbeater & Morton, 1974b). Of these only the recent studies by Hibberd (1975), Laval (1971), Leadbeater & Manton (1974), Leadbeater (1974) and Leadbeater & Morton (1974b) contain micrographs of material processed by modern methods.

Nutritionally, there are three basic types of Dinophyceae: (1) free-living photosynthetic autotrophs; (2) parasitic heterotrophs living on or in other organanisms and (3) free-living phagocytic or chemosynthetic heterotrophs. Representatives of the first type, the free-living photosynthetic autotrophic species, have been extensively investigated at the fine-structural level (for a review see Dodge, 1971). There are fewer species of the second type, the parasitic Dinophyceae, but many of these have been investigated in the electron microscope (Cachon & Cachon, 1966, 1970, 1971a, b; Cachon et al. 1968; Soyer, 1969 c; Manier, Fize & Grizel, 1971; Siebert & West, 1974). The third type, the free-living heterotrophic Dinophyceae, probably comprises the greatest number of species in the class; as Kofoid & Swezy (1921) state ‘One cannot work with the marine unarmored Dinoflagellata for even a short time without being struck by the fact that the majority of the individuals observed show evidence of holozoic nutrition and that the number actually containing chromatophores is relatively small throughout the entire Dinoflagella’. While the free-living heterotrophic Dinophyceae comprise the largest proportion of the class they have been, by far, the most poorly studied at the fine structural level. Investigations on these organisms have been limited to a comprehensive study of Oxyrrhis marina (Dodge & Crawford, 1971a, b, 1974) plus studies on specific parts of Cryptothecodinium cohnii (Kubai & Ris, 1969; Pokorny & Gold, 1973) and Noctiluca miliaris (Afzelius, 1963; Soyer, 1968, 1969a, b; Zingmark, 1970).

Southward & Butler (1972) discussed changes in sea and air temperature in the Plymouth area this century, and showed that there was an increase from about 1900 to 1945 followed by a decrease. In the present analysis the data, updated to 1974, have been subjected to a more rigorous statistical treatment, made possible by the availability of a computer; inshore and offshore sea temperatures have been compared in greater detail, and sea-bed temperatures included. The results are described and discussed in relation to the biological changes that have been observed in the western English Channel during the same period. Data on rainfall and westerly weather have also been examined, and correlated with the temperature values.

The amplitude and phase of tidal characteristics in the English Channel have been described both using numerical models (Grijalva, 1962; Hyacinthe & Kravtchenko, 1967) and a hydraulic model on a rotating table (Chabert d'Hières & le Provost, 1970). The aim behind the development of the numerical model described here is first to derive an accurate representation of the principal lunar semi-diurnal (M2) tide in the English Channel and then to use the currents generated by the tidal input to determine the tidal circulation patterns and residual flow through the English Channel. A test of the model must be its ability to reproduce the known clockwise eddy in Lyme Bay and the south-ward flow either side of Portland Bill. If these known tidal residuals can be reproduced then the model may help to elucidate residuals in other regions where the flow is unknown. In addition to deriving the mean tidal velocities, horizontal distributions for the mean squared and cubed values are calculated and the importance of these distributions in determining the nature of the bottom and the degree of stratification of the water column in summer is demonstrated.

Although the nitrogenous excretory products of a number of marine bivalve molluscs have been identified (Hammen, Miller & Geer, 1966; Hammen, 1968; Emerson, 1969; Allen & Garrett, 1971; Bayne, 1973 a) and average values for rates of nitrogen excretion recorded for some species (Lum & Hammen, 1964; Hammen et al. 1966; Bayne, 1973a), there is little information available on the ways in which environmental factors may affect either the balance between the various nitrogenous end-products, or their rates of excretion. The most thorough investigations have dealt with the effects of reduced salinity, which causes an increase in the rates of excretion of ammonia by Macoma inconspicua (Emerson, 1969), Mya arenaria (Allen & Garrett, 1971) and Mytilus edulis (Bayne, 1975). Dilution of the medium is also known to accelerate the loss of amino acids from the body, as part of the mechanism of volume regulation (Pierce & Greenberg, 1972, 1973). There is some evidence of altered rates of excretion during starvation (Hammen, 1968; Emerson, 1969; Bayne, 1973 a, b) and differences in excretion rate due to differences in animal size have been documented for Donax vittatus by Ansell & Sivadas (1973) and for Mytilus californianus by Bayne, Bayne, Carefoot & Thompson (1976 a, b).

The results of experiments recorded by Bayne & Scullard (1977) confirmed earlier studies (Bayne, 1973) in describing a decline in the rate of oxygen uptake (Vo2) by Mytilus edulis during starvation, eventually reaching a steady-state value, called the standard rate of oxygen consumption. Earlier experiments had also shown that if such starved mussels were fed, oxygen uptake increased rapidly to a high level called the active rate of oxygen consumption (Thompson & Bayne, 1972; Bayne, Thompson & Widdows, 1973). Some of this increase in metabolic rate is undoubtedly due to an increased filtration rate that is stimulated by the presence of food (the ‘mechanical cost of feeding’ discussed by Bayne et al. 1976), and part is due to the ‘physiological costs of feeding’, which includes energy utilized in digestion and assimilation of the food, and energy that is lost during deamination and other catabolic processes that accompany digestion (Warren & Davis, 1967). Increases in metabolic rate associated with feeding have been called the specific dynamic action (SDA) of the ration (see Harper, 1971, for a discussion) or the apparent SDA (Beamish, 1974)5 and they have been related to aspects of protein metabolism (Krebs, 1964). This paper describes the results of some experiments designed to examine the relationships between SDA and ammonia excretion in Mytilus edulis L.

Species of Haliotis are of economic importance in several countries around the world and the ormer Haliotis tuberculata (L.) is of importance in the Channel Islands off the north coast of France.

Wide-ranging surveys of the sea-bed and of its fauna may be made either from sledges or similar vehicles towed along the bottom, or from free-floating manned or unmanned submersibles. In general, towed sledges involve less sophisticated equipment because the needs for units for forward propulsion and for maintenance of a floating body at a specified distance above bottom are absent. However, sledges lack the manoeuvrability of submersibles, and are more likely to be fouled by obstructions on the sea-bed.

A number of species of ophiuroid are known to occur in dense clusters on the sea-bed. Aggregations of Ophiothrix fragilis (Abildgaard) have been recorded from the English Channel by Allen (1899), Vevers (1951, 1952), Barnes (1955), Ancellin (1957), Cabioch (1961, 1967, 1968), Holme (1966), Warner (1969, 1971), and by Allain (1974). Beds of the same species have been found in the Irish Sea by Jones (1951) and by Brun (1969), on the west coast of Ireland by Könnecker & Keegan (1973) and Keegan (1974), and on the west coast of Scotland, where it is widespread in sea lochs and elsewhere around the coast (McIntyre, 1956, and personal communication, 1975). Records of Ophiothrix fragilis from the North Sea have been summarized by Ursin (1960). In the Mediterranean, aggregations of Ophiothrix quinquemaculata (D.Ch.) have been described by Guille (1964, 1965) from off the south coast of France, and by Czihak (1959) from the Adriatic. Hurley (1959) gives underwater photographs of Ophiocomina bollonsi Farquhar from the Cook Strait, New Zealand. Further examples of aggregation in ophiuroids and other echinoderms are cited by Reese (1966), Mileykovskiy (1967) and by Warner (1978).

The small hermit crabs of the genus Clibanarius are mainly found in tropical regions but one of them, C. erythropus (Latrielle), is common along Mediterranean shores (Holthuis & Gottlieb, 1958); this species was formerly known as C. misanthropus (Risso), but the name C. erythropus has priority (Forest, 1958) and is now in general use. Outside the Mediterranean the species ranges from Brittany to southern Morocco and the Azores (Holthuis & Gottlieb, 1958; Zariquiey Alvarez, 1968). In 1955–7 the extreme northern limit in Brittany was placed at Melon, between Brest and Trémazan (Crisp & Fischer-Piette, 1959); these workers, and also Carlisle & Tregenza (1961), were apparently unaware that the crab had been discovered at Roscoff, on the north coast of Brittany in 1955 (Rullier, 1959; Thiriot, 1965; Bourdon, 1965).

Pillai (1970) proposed that the Spirorbidae form a distinct family and, though closely related to serpulids, they are indeed more surely separate than many families of birds and insects. Their study in Britain was well begun by Montagu (1803), with so much ecological detail that most of the species in his account (about ten) can be recognized by anyone who is really familiar with the marine fauna of Devon. All the names which he used, however, have lapsed or been applied otherwise, except Spirorbis spirorbis L. and even that has often been called S. borealis. Some of the nomenclature of McIntosh (1923) has similarly lapsed, because it conflicted with clear descriptions by French and Scandinavian authors, including Fauvel (1927).

It is our aim in this paper to answer three questions. All of them relate to the well-known ability of lugworms to act as isosmotic osmo-conformers over a wide range of salinities. When exposed to diluted sea water, the body fluids come into osmotic equilibrium with the lowered external concentration, and considerable amounts of water enter the body of the worm. There is no evidence of weight or volume regulation in dilute media, as assessed by a return of the body weight towards its original value. The processes of osmotic adaptation down to the lowest salinity limits for survival include, therefore, tolerance of a lowered osmotic concentration of the body fluids, and of the retention of increased amounts of water in the body. The evidence on which this view of osmotic adaptation in lugworms is based is reviewed by Oglesby (1969, 1973). Additional information on Arenicola marina is provided by Freeman & Shuttleworth (1977).

There has been some confusion over the past 150 years or so concerning the correct combination to be applied to the single species of hydroid variously known as Arum cocksi, Myriothela phrygia and M. cocksi. The correct binominal would seem to be Candelabrum phrygium, a combination first used by de Blainville (1830) but hardly used since. An attempt by Stechow (1921, 1922, 1923) to re-introduce this combination has apparently been unsuccessful. The synonymy relevant to the genus name is as follows. To avoid repetition some information more relevant to the nomenclature of the species name is also included here.

Many of the calanoid copepods contain large amounts of neutral lipid that is predominantly wax esters (Lee, Hirota & Barnett, 1971; Lee & Hirota, 1973; Sargent & Garten, 1976). The role of these compounds in the life-history of copepods is particularly well documented for the large Northern Pacific calanoid Euchaeta japonica Marukawa. These animals have their highest levels of total lipid (50% of the dry weight) at stage V, up to 80% being wax esters (Lee, Nevenzel & Lewis, 1974). Wax ester levels are lower in adult females but are high in the eggs, the contents of which are subsequently used during the naupliar stages (Lee et al. 1974). Thus, wax esters accumulated during the later developmental stages provide a fuel for the developing eggs and embryos; from which it follows that the amounts of these lipids present in mature animals are likely to be critical in determining the brood size and survival of the ensuing generation. So far, however, the factors controlling lipid levels in copepods have been poorly understood.

This paper is concerned with a re-examination of the pattern of nerve activity from receptors in ray fin muscles in response to stretch applied to the muscles. In earlier work receptors have been found in the fin muscles of elasmobranchs, those in rays being described in a recent paper by Bone & Chubb (1975 - which see for references to earlier anatomical work) and physiologically by Fessard & Sand (1937). The receptors are supplied by myelinated axons, and the endings take the form of beaded nerve strands associated with congregations of connective tissue lying between muscle fibres. In the pectoral fin muscles these structures lie between small-diameter muscle fibres, with multiple motor nerve endings, which occur superficially in the muscle. Most of these muscle fibres show a positive staining reaction for succinic dehydrogenase (SDH) and lipid, though some are negative for SDH. They contrast with the larger fibres, which show negative staining reactions for SDH and lipid, andhave focal motor innervation. The latter make up the bulk of the muscle (Bone & Chubb, 1975). It seems very likely that most of the small fibres are slow contracting (possibly with no propagated action potential in the muscle fibre), and the large fibres are of a twitch type. This would parallel the arrangement in dogfish myotomes (Bone, 1966). Bone & Chubb consider the coupling between the endings and the muscle fibres to be generally loose, although they also describe occasional sites of much tighter coupling. Such small muscle fibres are particularly concentrated in a superficial and rather discrete part of the muscle, here called the tonic bundle and used in the present experiments as an isolated preparation.

In November 1969 on ‘Discovery’ Cruise 30 a day and a night series of hauls were taken with the RMT 1 + 8 net system (Baker, Clarke & Harris, 1973) in the region of the Cape Verde Islands. The cyclopoid copepods from the two series have been examined and this account describes their depth distributions, vertical migration patterns and community organization. Some taxonomic observations on one family, the Oncaeidae, have already been published (Boxshall, 1977).

The freshwater medusa, Craspedacusta, has been taken again in its classic semi-natural locality, the Exeter Canal. While tow-netting for freshwater plankton on 15 September 1976, in connexion with a study of the food of endemic fish populations, one male specimen of the olindiadid limnomedusan Craspedacusta sowerbyi Lankester (1880) was found. The locality was 300 m on the Exeter side of the Turf Lock (map reference SX 963863) and the net, mesh size 50 mpi, was being towed from a small rowing boat at a depth of approximately 1 m at noon in weather of occasional sunshine, the water temperature being 20 °C.