The lophophore of Platidia, as illustrated in most memoirs and text-books, bears little resemblance to its appearance in life, no doubt because such illustrations and the accompanying descriptions were based on dried specimens. The lophophore of Platidia has been considered to be of a peculiar sigmoid type, differing from that of any other known lophophore. The dredging by R.V. ‘Sarsia’ of three species of the genus in recent years has afforded the opportunity of figuring the lophophore in its natural state, and the working out of its growth stages in P. davidsoni and P. anomioides: these were previously unknown for any species of Platidia. The third species, a new one, is described separately (Atkins, 1959).

Age and growth of Loligo vulgaris and L. forbesi were studied by the examination of growth increments in 96 and 135 selected (white zone <10%) statoliths, respectively. Squid were obtained by monthly sampling from the catches of commercial trawling and hand-jigs in Galician waters (north-west Spain) between February 1991 and October 1993. Mantle length (ML) of L. vulgaris ranged from 70 to 480 mm and varied between 70 and 685 mm in L. forbesi. A negative allometry between statolith length and ML or body weight (BW) was found in both species. Sexual dimorphism was apparent in both species, males grew faster and longer than females. The statolith analysis suggests that growth patterns of L. vulgaris and L. forbesi in Galician waters are different. The exploited population of L. vulgaris was composed of two groups: one formed by individuals hatched in winter–spring and another by specimens hatched in summer–autumn. Squid hatched in winter–spring reached larger sizes at the same age than those hatched in summer–autumn. These two groups were also observed in L. forbesi. However, squid of this species hatched in winter–spring were smaller than those hatched in summer–autumn at the same age. Reasons for this discrepancy are discussed. The life span of L. vulgaris was about one year whereas the life span of L. forbesi extended to 18 months.

Records of nearly 2000 dogfish collected from the Ilfracombe region suggest that the spawning season of this fish starts in November and continues at least until July. This area probably represents a spawning ground into which the females migrate during the spawning season; the males follow them much later in April and May.

Figures are given to show the time taken at different temperatures for the embryo to develop to a series of definite morphological stages; these suggest that the temperature characteristic of the development (µ = 20,000) is substantially the same as for several teleost species.

The geographic distributions of most surface-dwelling species of planktonic Foraminifera are now well-known (Bé, 1959, 1960, 1977; Bé & Hamlin, 1967; Bé, Vilks & Lott, 1971; Bé & Tolderlund, 1971; Tolderlund & Bé, 1971; Bé & Hutson, 1977). These distributions, established from species abundance in plankton net collections, have been used to correlate abundance with physical and chemical variables (primarily temperature and salinity) in an effort to establish the factors which control the geographic range of these shelled protists. Significant correlations have been derived from these comparisons and the temperature and salinity ‘limits’ and ‘optima’ of a number of species have been reported (e.g. Bé & Tolderlund, 1971).

Biodiversity of cnidarian and ctenophore forms in Toyama Bay, Japan Sea, was lower than that in Sagami Bay, north-western Pacific, according to all the indices investigated. Highest richness of forms occurred in the 400—600 m depth layer in Sagami Bay, while in Toyama Bay richness was low in most layers. New forms continued to occur with increasing depth in Sagami Bay but not in Toyama Bay and species composition differed remarkably between the two bays. Putative secondary deep-sea gelatinous forms were identified. Horizontal patchiness in normalized abundances was the rule rather than the exception and for accurate calculations of biodiversity indices incorporating evenness or equitability, the necessity for multiple submersible dives in a single area and survey period was noted. Vertical migration and predation were identified as possible factors contributing to the higher diversity in the 400—600 m depth layer in Sagami Bay.

There are few teleosts which depart from the ‘classical’ ichthyan body form to such an extent as the seahorse, Hippocampus. In this genus the caudal fin is absent and the tail has become prehensile, the usual function of the caudal fin is taken over by the dorsal and pectoral fins. The dorsal and pectoral fins both have a sculling action, the small anal fin moves ‘bodily’ through the water from side to side.

In the past, interest has generally centred on fast moving fish, which have evolved a limited number of body forms, as few variations are possible without a sacrifice of speed. The evolution of the swimming mechanisms of these fish has favoured an increase in the maximum speed and acceleration. In relinquishing the demands of speed the seahorse has released itself from restrictions which would limit its possible range of form.

The structure of the thecae, as seen in the electron microscope, are described for two species of Prorocentrum and five of Exuviaella. For the first time it is possible to distinguish between true pores and the spines and thin areas of wall which have previously been described as pores or poroids. Several distinct features such as the spines covering the valves, the ridged valve margin and special flagella pore structures which are found in only two of the Exuviaella species suggest that it may be necessary to create a new genus.

Diversity is one of the most important parameters used in the description of a community; several theories relating diversity to other phenomena as predation, competition and stability have been proposed (Pianka, 1966). As a result of the increasing interest in diversity a number of studies have appeared during recent years, but the meiofauna has until recently been almost completely neglected, rather surprisingly when one considers the importance of this group of organisms in all marine benthic communities. Coull (1972) studied recently the diversity of harpacticoid copepods, with nematodes the major meiobenthic component, along the North Carolina shelf and in the deep sea. Warwick & Buchanan (1970) appear to be the only ones to have studied diversity in nematode communities, using α of the logarithmic series (Fisher, Corbett & Williams, 1943) as a diversity measure. The paucity of data seems primarily to be due to the taxonomic difficulties encountered in studying nematodes.

The sea urchin Psammechinus miliaris was sampled at monthly intervals from two replicate sites at contrasting locations (littoral and subtidal habitats) on the west coast of Scotland. Samples were collected from November 1995 to October 1997. A study of gonad development showed a clearly defined annual cycle of gametogenesis with a single spawning period. Gonad indices (GIs) varied between locations, between sites at the same location and between study years. Gonad indices were maximal prior to the onset of the spawning period in June and July. Ripe gametes were shed by dissected urchins from June to September in 1996 and June to August in 1997 coinciding with the time of year when the gonad colour was best in terms of what is desired in the market place. Over winter the GIs were very low and gonads became very dark in colour. Higher summer GIs in the urchins from one littoral site suggested that the urchins there had a seasonal influx of a more nutritious or more abundant food resource. Histological determination of the reproductive state showed that for these food-limited populations high GIs do equate with the spawning period. The gametogenic cycle fits the six stage pattern described for other echinoid species. In females oocytes of various developmental stages were present throughout the annual cycle. Recruitment to the littoral location was monitored over two seasons by quantifying the number of urchins with a test diameter <5 mm appearing in the population. Recruitment appeared variable between sites and between seasons suggesting that the collection of juveniles resulting from natural settlement may not be a reliable alternative to hatchery produced spat. Although P. miliaris has commercial potential when in cultivation, this study provided no evidence of an opportunity for a commercial fishery.

In Ireland the purple sea urchin Paracentrotus lividus (Echinoidea) typically inhabits intertidal bored holes. At Lough Hyne, Co. Cork, a population occurs associated with rock scree in the shallow subtidal zone. This study provides unequivocal quantitative evidence to demonstrate diurnal migration in a population of P. lividus at Lough Hyne, Ireland. Most size groups/age-classes did not to migrate, the youngest always and oldest never occurring under rocks. Those that did migrate between the lower and upper surface of rocks (2+, 3+ and 4+ age categories) did so in exactly the reverse circadian pattern to those described from the Mediterranean Sea.

Mature eggs were stripped from ripe adult specimens of Arctica islandica and exposed to a dilute solution of ammonium hydroxide for various lengths of time before addition of stripped sperm. Larval and early post-larval stages were cultured under experimental laboratory conditions using standard bivalve rearing techniques. Larval cultures were maintained at various controlled temperatures ranging from 8·5 to 14·5 °C. Minimum time to settlement was 32 days at a temperature of approximately 13 °C; at temperatures between 8·5 and 10·0 °C, settlement was not observed until approximately 55 days after fertilization. Larval growth rates were significantly faster at temperatures between 11·0 and 145 °C than at temperatures between 8°C. Morphometry of the larval shell and morphology of the larval hinge apparatus were independent of larval growth rates and experimental culture conditions.

The present study investigates the species distribution patterns and macrofaunal assemblages along the English Channel and the environmental factors contributing to observed patterns. Seven distinct macrofaunal assemblages were identified based on Hamon grab samples. In the western Channel, an Echinocyamus/Nemertea assemblage dominated, giving way to an Abra/Scalibregma assemblage in inshore waters. A Verruca/Sabellaria assemblage was identified to occupy large regions of the mid-Channel while those of the east Channel were more spatially variable. While variations in depth, sediment particle size and wave and tidal stress were significantly related to variations in assemblage structure, temperature did not appear to be greatly influential. In addition, acoustic data obtained for each station sampled allowed us to determine how representative the observed biological communities are over spatial scales somewhat larger than the sampling points. In contrast to earlier comparable studies using anchor dredges, the biological communities sampled in this study did not exhibit a large east–west distinction; the most abundant species and key assemblages were found to be present along the length of the Channel. The possible reasons for these differences with earlier studies are discussed.

A seasonal survey of particulate and dissolved organic material was made at E1 in the English Channel during 1968. The average integral mean values were: dissolved organic carbon 65 μg-at C/l (780 μg C/l); dissolved organic nitrogen 4·6 μg-at N/l (64 μg N/l); dissolved organic phosphorus 0·12 μg-at P/l (3·8 μg P/l); particulate organic carbon 190 μg C/l and particulate organic nitrogen 21 μg N/l. Dissolved organic carbon and the particulate organic carbon and nitrogen showed increases subsequent to the spring bloom; such increases were less evident in the dissolved organic nitrogen results and not apparent in those of dissolved organic phosphorus.

Analyses were also made in March and June in 1969 at two other stations in the English Channel, in addition to E1. The results from the three stations were basically similar.

1. The larva of a Terebellid which is very common in plankton from the Plymouth district during spring has been reared and proved to be the young of Loimia medusa Sav. This larva is characterised by its very large gelatinous tube.

2. The development of the external structures is described from a stage in which the first tentacle was just appearing to a juvenile stage in which all the main characters of the adult had been assumed.

3. The building of the first sandy tube on the bottom is described.

4. The development of the bristles and uncini are dealt with in some detail and a comparison made with the corresponding development in Nicolea zostericola. Evidence of the suppression of a pair of larval bristle-bundles in Loimia is indicated.

5. Previous records of Loimia larvse are discussed.

6. McIntosh's separation of our British Loimia to a new species, L. montagui, is shown to be probably unjustified.

The germ cells of Polydora ciliata arise from cells lying just inside the ventral epithelium and later migrate into the gonads. They are released into the coelom when they are 30 μ in diameter and are transported posteriorly to the region of maturation. The eggs and sperm are shed through the modified nephridia of the region of maturation. The eggs are laid into a string of capsules apparently secreted by the nephridia and attached to the wall of the tube. The larvae take about a week to hatch and are released into the plankton at the three chaetiger stage. They spend some 6 weeks in the plankton before metamorphosis, and have grown to 17 or 18 segments. Monthly samples of the worms living in the London clay at Whitstable in 1956 showed that the population was bimodal with respect to size and the two groups of adults gave rise to two larval settlements in late March and May. The two groups of juvenile worms that developed from these larvae retained their identities through the summer and the following winter. There is no apparent morphological character by which the adults of each type may be recognized, the time of spawning and the lower fecundity of the early breeding worms being the only distinguishing features. It is suggested that these groups are the consequence of an overlap of two populations of P. ciliata from different centres of distribution, each being adapted in its breeding requirements to a different part of the temperature range.

The geographical distributions and seasonal cycles of pelagic larvae and post-larval stages of decapod Crustacea in the north-eastern Atlantic and the North Sea during 1981–3 are described from samples taken with the Continuous Plankton Recorder (CPR). Analyses of the distributions of 36 common taxa identified groupings which could be related to depth and temperature. The seasonal occurrences of planktonic larvae of benthic taxa were found to be correlated with sea-bottom temperature in the winter as well as parameters of the sea-surface temperature. Possible interpretations of these data are discussed.

Allozymes and restriction fragment length polymorphisms (RFLP's) in genes of the NADH dehydrogenase complex (ND 5/6 genes) of mitochondrial DNA (mtDNA) were used to investigate the spatial genetic structure of Atlanto-Scandian herring (Clupea harengus). Samples (sample size=46–50/site) comprised Icelandic summer spawners, Norwegian spring spawners, and two fjord populations, Balsfjord and Trondheimsfjord, on the Norwegian coast. Fifty enzymes were assayed, and samples were routinely examined at 18 enzymes comprising 28 putative allozyme loci. Significant genetic differentiation (P < 0.001) was detected between Trondheimsfjord herring and all other samples, with apparent genetic homogeneity among remaining samples, including the Balsfjord; a region shown previously to contain an allozymically distinct population. Herring from the Balsfjord were shown allozymically to represent the Norwegian spring spawning group, suggesting the presence of two stocks, a deeper resident spawning (Balsfjord) and a shallower, non-native feeding population (Norwegian spring spawning). Variation at the ND5/6 genes using six restriction enzymes revealed 96 composite haplotypes in 196 fish. Mean haplotype diversity was high (0.92), though nucleotide divergence between samples was small (highest=0.00029, between Trondheimsfjord and Balsfjord samples; lowest=0.00003, between Icelandic summer and Balsfjord samples). Monte-Carlo %2 analysis of haplotype frequencies revealed no significant geographic heterogeneity among samples, thus revealing a discordant pattern of genetic differentiation produced by allozymes and mtDNA markers. The detection of a genetically divergent population in deeper waters of the Trondheimsfjord supports the existence of distinct deep-water resident populations in the Norwegian fjords.

INTRODUCTION

This paper forms the second and last part of a study of the vertical distribution and migration of pelagic Amphipoda based on material collected off Fuertaventura, Canary Islands, during the SOND Cruise in 1965. The first part (Thurston, 1976b) dealt with the Gammaridea. The data presented herein deal with the Hyperiidea, to which is added a general discussion.

The background to the cruise has been given by Currie, Boden & Kampa (1969), and Foxton (1969) has described the gear and methods used. This analysis is based primarily on samples obtained from a series of 1 m2 ring-net (N 113) hauls, but has been supplemented by selected materials from modified 3 m Isaacs-Kidd Mid-water Trawl (IKMT), neuston net and 1 m2 Rectangular Mid-water Trawl (RMT 1) hauls. Thurston (1976b) has discussed the limitations of the sampling techniques as they affect the present results.

A tagging investigation on the ormer (Haliotis tuberculata L.) has been carried out for the Guernsey States Sea Fisheries Committee. Cementing plastic discs to the shell has proved a satisfactory technique since substantial numbers of 40—50% were recovered after 1 and 2 years in the open sea off the west coast of Guernsey. From the increase in shell size of the recovered specimens the mean growth rate has been shown to be about 15 mm of shell length per year up to a shell size of 50 mm, and thereafter decreasing until at 100 mm length growth is negligible. The growth parameters K and L∞ have been calculated. Annual rings were frequently, though not invariably, found on the shell. From the frequencies of the shell-ring lengths in the smaller ormers estimates of the shell size reached 1 and 2 years after settlement have been made. A single annual ring was also found with the majority of the larger shells (> 50 mm), though when growth did not exceed 4 mm in a year the rings were not included owing to the difficulty of separating annual rings from possible disturbance rings caused by the process of tagging. The position of the annual ring varied, being closer to the outer edge of the shell with increasing size. Measurements of the length increase from one annual ring to the next indicated rates of growth closely comparable to those obtained from tagging measurements. Damage to the shells by the boring sponge Cliona lobata Hancock is very widespread, particularly in the larger ormers living below the tide marks.

Records of cirral activity have been made over periods of 24–48 h for individual specimens of eight species of barnacles from three different localities. The effects of movement, gas content, and hydrogen-ion concentration of the water have been studied.

In still water most species eventually settle down to a more or less steady rhythm (activity rhythm) of short bursts of cirral beating interspersed with inactive periods. Two exceptions are the surf- or current-loving species Balanus cariosus and Tetraclita squamosa which remain inactive or eventually cease activity. In moving water all species show practically continuous activity, the velocity of the flow needed to produce this response varying according to the species, habitat, and previous history of the specimen. Increased oxygen content has less effect on activity than other factors studied, but eventually appears to reduce activity. A gradual reduction in oxygen content first leads to increased activity and then signs of distress attributable to anoxia.