Patella vulgata were excluded from barnacle dominated areas at Port St Mary, Isle of Man by wire fences attached to the rock in September 1977, December 1977, April 1978 and July 1978. The sequences of algal colonization of these exclusion areas differed markedly with season: in autumn diatoms were followed directly by Fucus, in winter and spring diatoms were followed by green algae and then Fucus, and in late summer Fucus sporelings arose directly on the barnacles. There was no evidence that the initial stages were necessary for the subsequent recruitment of Fucus.

A new species of Chrysochromulina Lackey with exceptionally long cylinder-scales distributed evenly over the cell is described and illustrated with electron micrographs of shadowcast whole mounts of wild material from the Galapagos Islands, South Africa and the English Channel. In all cells, the cylinder-scales are underlain and outnumbered by highly characteristic plate-scales, each with a conspicuous infra-marginal ridge on the distal face. Some consistent dimensional and other differences between periplasts from Africa and the Galapagos Islands are noted, with the British equivalents approximating more closely to the former though with minor differences from both. The observations are interpreted in a preliminary way, but further comment including comparisons with other taxa will follow.

As aids to the phyletic interpretation of the newly described Chrysochromulina pachycylindra Manton et al., some hitherto unrecorded gatherings of C. microcylindra Leadbeater and C. cyathophora Thomsen, from South Africa and South Alaska respectively, are introduced, thereby amplifying the type descriptions of both species, which were previously known only from Europe. Characters shared between C. pachycylindra and C. microcylindra are numerous, including a capacity for transverse fracture of their cylinders not previously noted in the latter. This suggests an exceptional degree of affinity between these two species in spite of gross differences in relative dimensions of different parts of their respective cylinder scales. On the other hand the general resemblance between C. microcylindra and C. megacylindra (Leadbeater, 1972), previously noted, is unaffected by these findings and it is concluded that all three species could be treated as a closely related subgroup within the genus Chrysochromulina. In contrast, C. cyathophora is shown to be so different as to be interpretable only in terms of parallel evolution from a separate prototype source, the plate-scales in particular being so far unique in the genus in being thin, rimless, peculiarly patterned and convex when seen in section. The mere presence of cylinder-scales is thus seen to be insufficient evidence of phyletic affinity unless confirmed by other characters, among which the details of the plate-scales are probably the most important.

It is suggested that the cumulative view of growth in which some index of biomass is plotted against time tends to obscure temporal variations in the growth process that might provide evidence of how it is controlled. Experiments with the colonial hydroid Campanularia flexuosa show that the action of a growth control mechanism can be demonstrated by considering changes in specific rates of growth determined at frequent intervals in time. However, it is also necessary to disturb the growth process slightly in order to initiate the action of the control mechanism, and having done so, to isolate the effect of the disturbance on growth and thus the action of the control mechanism. This is done by expressing the specific growth rate of organisms whose growth is disturbed as a percentage of that of control organisms of the same age.

Valve structure was investigated using light and scanning electron microscopy and each valve was found to comprise four layers; periostracum (dorsal), tegmentum, articulamentum and hypostracum (ventral). The penetration of the valves by the aesthetes within channels is described and three distinct types of aesthete channels are identified, namely, multiple branch aesthete channels, slit ray aesthete channels and jugal sinus aesthete channels. The distribution of the different aesthete channels within the various valves is defined and their relationship with the valve external sculpturing is described. The process of valve growth by marginal increment is discussed in relation to the formation of the aesthetes.

The intertidal distributions of the two varieties of Actinia equina L. defined by Stephenson (1935), var mesembryanthemum and vai.fragacea, have been studied on several shores of the English Channel. The reproductive physiology and iso-enzyme genetics of sympatric populations of the two taxa have been investigated in greater detail on one shore. The genetic results show that the two taxa are reproductively isolated and, overall, the evidence indicates that they are separate species.

The ciliated epithelial sensory cells of the tentacle papillae and of the concave epipodial sense organ (e.s.o.) surface of the trochids Margaretes helicinus, Gibbula cineraria, G. umbilicalis, Monodonta lineata, Diloma nigerrima and D. zealandica are primary sensory cells with intra-epithelial nuclei. The 5–7 cells of a single papilla bear many cilia. Each e.s.o. cell has one cilium surrounded by 8–9 specialized microvilli. Both kinds of sensory cell show structural similarities with known mechanoreceptors.

Closed circuit underwater television observations showed that, in summer, large numbers of Carcinus maenas performed daytime tidal migrations up and down a small mudflat in the Menai Strait, North Wales. At the observation point, 25 m above mean low water mark of spring tides, numbers of crabs moving upshore on flood tides averaged 84 m—1 of tideline, ranging from 48 to 126 m—1. Most crabs were of 20–50 mm carapace width (1 and 11 groups); none smaller than 15 mm was seen. Peak movements occurred in at least 0.5 m depth of water. Over the high tide period, most crabs were dispersed over the upper half of the mudflat where crab population densities of 1·8–2·5 m—2 were indicated by diving observations.

In shallow hypoxic sea water female shore crabs (Carcinus maenas (L.)) incubating eggs on their abdominal pleopods reverse the direction of normal ventilation, taking air in at the normally exhalant opening and bubbling it out via apertures at the base of the posteriormost pair of walking legs and hence over the developing egg mass. The ambient oxygen tension at which the behaviour is elicited and the percentage of total time it is performed are both dependent upon acclimation temperature. The oxygen tension at which the behaviour is first observed coincided at different acclimation temperatures with the critical oxygen tension below which oxygen consumption of the developing eggs became dependent on further reduction in . The bubbling of air during the emersion response is sufficient to raise the oxygen tension of the water surrounding the eggs and is thus an attempt by the parent animal to maintain the oxygen uptake of the developing young. If left in a standing body of hypoxic sea water release of larvae is deferred until well-aerated conditions next prevail. Thus if the berried female is trapped in a rock pool the encroaching tide may act as a releasing stimulus which is of adaptive significance to the dispersal and survival of the larvae. When female crabs submerged in warm water (25 °C) bubbled cool air past the egg mass this had no significant cooling effect. The thermal tolerance of the developing eggs was low, rate of oxygen uptake being limited by temperature rises above 25 °C.

Whole body cooling of dogfish initially anaesthetized with MS 222 produced total immobility and permitted prolonged surgical procedures. Additional anaesthesia was not required, and on rewarming recovery was rapid.

Electromyographic recordings of jaw-closing and fin-elevating reflexes of the dogfish during body cooling indicated that processes within the central nervous system were being blocked and that the effect was most pronounced on polysynaptic reflexes.

Aricidea laubieri sp.nov. and six other species of the Paraonidae new to the British Isles were found during benthic surveys in the Celtic and North Seas. These increase the number of British representatives of the family to 15. New records of a further seven species are given, which in several cases extend the known geographical or bathymetric range. The identity of some previous records attributed to Aricidea Jeffreysii (McIntosh, 1879) and to Aricidea suecica Eliason, 1920, is discussed. A dichotomous key to British species is presented.

Turbulence measurements taken at the water's edge at Derbyhaven beach, Isle of Man, indicated that maximum turbulence on any particular tide predictably occurred at the time of high water. However, long term monitoring failed to record any predictable semi-lunar modulation of the intensity of turbulence. Laboratory experiments showed that cycles of mechanical agitation applied for 2 h every 12 h for 4 days could entrain the endogenous circa-tidal activity rhythm of adult Eurydice pulchra. The effect was the same with shaking in constant light or constant darkness. However, when applied at different phases of an imposed L/D cycle, the synchronizer had a varying effect. The strongest entrainment occurred when shaking was phased to ‘midday’ and ‘midnight’ - a phase relationship paralleled by the high water of spring tides. Minimal synchronizer effect occurred when shaking was applied at ‘dawn’ and ‘evening’, the phase relationship of neap tide high water to the solar day. The varying response is suggested to be the origin of the semi-lunar modulation of activity seen in Eurydice pulchra.

The luminescence of a number of amphipods of the genera Scina, Parapronoe, Cyphocaris, Megalanceola, Thoriella and Chevreuxiella/Danaella is described. The flashes of Scina spp. are rapid, 80–300 ms in duration, and may be elicited repetitively by electrical stimuli. Cholinesterase inhibitors are potent inducers of luminescence both in whole animals and in isolated appendages. A characteristic postural response is usually associated with mechanically induced luminescence of the larger species of Scina. Cyphocaris and Chevreuxiella/Danaella species also respond to electrical stimuli but the luminous responses are of longer duration than those of Scina and are not stimulated by eserine sulphate. In Parapronoe luminescence can be most easily induced with dilute hydrogen peroxide and the photogenic cells are associated with a brown pigmented area restricting the light output to a ventral direction. Secretory luminescence has been observed only in Megalanceola.

Skin structures of nine different species of dorid nudibranchs were examined at the scanning electron microscope and the light microscope levels. From these observations the animals are grouped into three categories.

1. Dorids with spicule-supported tubercles carrying a sensory knob (Rostanga rubra, Jorunna tomentosa, Onchidoris sparsa, Onchidoris pusilla).

2. Dorids with small sensory papillae set in pits and distributed randomly between projecting spicules (Aegires punctilucens).

3. Dorids with tubercles differing in shape from one species to another, invested with numerous spicules but without conspicuous sensory structures. The tips of the tubercles do, however, contain single sensory epithelium cells (Archidoris pseudoargus, Acanthodoris pilosa, Onchidoris muricata, Onchidoris bilamellata).

The development of the oocytes of Nereis (Hediste) diversicolor and Nereis (Nereis) pelagica takes up to 18 months from their first appearance in the coelom to maturity, and in the natural conditions experienced by the population studied in north-east England the females are in their second year before the oocytes begin to appear. The duration of spermatogenesis is less than that of oogenesis, taking up to 6 months for completion. This information permits a more rigorous interpretation of the size frequency data which have been obtained from a biometrical study of the jaws. In the populations of both species the majority of individuals seem to reach maturity when 3 years old.

An account is given of the variations of shape, colour and patterns of surface sculpture of the shells of ovoviviparous, upper-shore periwinkles of the Littorina ‘saxatilis’ speciescomplex from the sea-coasts and estuaries of south-west England. Variations of shell shape derive from the differing geometries of the helically coiled shell cone. The rate of expansion of the cone is constant in each individual shell, but varies in the component shells of a population and (more widely) between one population and another. The area of the shell aperture is a measure of the expansion rate. Samples of ‘saxatilis’ were taken from some 65 localities covering a wide range of shore environments and, whenever possible, at closely comparable tidal levels (the Pelvetia (P) belt/approx. to M.H.W.S.) and aperture measurements made of shells of all lengths from 1–10 mm (age ca. 0·1–2 years). The apertures of pre-emergent shells teased from the brood pouches of mature females, and of ca. 0·4–0·6 mm length, were also measured. Population aperture-size comparisons were founded primarily on subsamples of shells 10 ± 0.5 mm long - the P-10 aperture-size statistic; and the possible adaptive value of aperture (and foot) size variations were sought through matching relationships with varying conditions of wave attack, shore gradient, platform structure and other features, of which assessments were made in the field. Logarithmic plots of the sequences of aperture-size/shell-length measurements of pre-emergent and post-emergent shells show that the cone geometries are genetically determined, and there is some evidence of the adaptive selection of some geometries and ranges of aperture size in preference to others, mostly in the early post-emergent stages of growth

An experiment was performed to assess the productivity, food chain efficiency and nitrogen conversion efficiency of a semi-closed nursery system for bivalve spat held in upwelling columns. Algal blooms were encouraged by nutrient enrichment of onshore tanks and maintained for short periods under grazing pressure from bivalves.

Globigerinoides sacculifer (Brady), a common planktonic foraminifer collected by SCUBA off Barbados, was maintained under six feeding regimes at constant light and temperature conditions. Five groups of 63 specimens each were fed 1-day-old Anemia at the rate of one nauplius per specimen every 1, 2, 3, 4 or 7 days. A starved control group received no Anemia. The rate of chamber formation and shell size increased proportional to the feeding frequency. However, an inverse correlation existed between survival time and feeding frequency. Normally, survival time ends with gametogenesis which terminates the life of the mother cell. Organisms fed more frequently reached maturity and underwent gametogenesis more rapidly than those fed less frequently. The average survival time of G. sacculifer in culture ranged from 7 days for the daily-fed group to 11 days for the group fed every 7 days. While the latter grew more slowly they eventually reached maturity. Starved individuals rarely formed chambers and often died without undergoing gametogenesis. Symbiotic zooxanthellae presumably prolonged survival of starved organisms. Extrapolation of survival data suggests G. sacculifer has a variable life span of 2 to 4 weeks depending on food availability.

In the course of benthic surveys carried out around the U.K. by the Oil Pollution Research Unit, a number of species of polychaete not previously recorded from British waters were found. A new species of Aricidea and six other species of the Paraonidae new for Britain have been described by Hartley (1981), and this note records a further five species taken either in the Firth of Forth (56° 19′ N, 3° 34.8′ W, 2–5–5 m depth, fine sand) or in the Forties oilfield (57° 44.0′ N, o° 54°0′ E, 100–130 m depth, fine to muddy sand) with 0.1 m2 Van Veen/Day grabs in September 1979 and June 1978 respectively. The sieve mesh used was 0.1 mm diameter.