The muscle fibres of the radial muscles of the unpaired fins of dogfish can be divided into two populations—an outer group of red muscle fibres which are smaller and fewer than the inner white muscle fibres and which differ in structure, number of nuclei and pattern of innervation. Two types of potential were detected in the two muscle systems when recordings were made with implanted electrodes during movements of the fins. The red muscle fibres were associated with small, slow junctional potentials which changed in amplitude when the activity of the system was altered.

A range of 27 marine phytoplankton species, representative of several of the principal classes, has been grown under similar conditions in Erd-Schreiber medium with abundant nutrients. Harvesting was carried out 20 days after inoculation while vigorous growth was proceeding. The component fatty acids of the lipids extractable with chloroform-methanol were determined by gas-liquid chromatography. In all, 40 fatty acids were determined. It is likely that the component fatty-acid distribution may be valuable for taxonomic purposes. Thus, specific fatty-acid assemblages may characterize particular Phyla or even classes. For example, the Bacillariophyceae are differentiated from the other organisms examined by the virtual absence of 18:2, 18:3 and 1814; the Cryptophyta are distinguished by their high content of 20:1. The fatty-acid arrays of species belonging to the same genus are frequently very similar, e.g. Dunaliella primolecta and D. tertiolecta.

Investigations on larval nematodes in herring revealed that Anisakis sp. larvae occurred in the body cavity of 34 % of 5646 juvenile and adult herring examined; and that the infection increased with increase in fish length (age) and varied with the locality, being greater in herring caught nearer to the British coasts. The effect of temperature and salt concentrations on the survival of the larvae and the public health hazards of the larvae were discussed.

A new midwater trawl based on that designed by Tucker (1951) is described with details of opening and closing equipment, acoustic release gear and depth telemetering pinger. An account is given of the method used in operating the xtrawl from R.R.S. ‘Discovery’.

A collection of 185 cephalopods from near the southern end of Fuerteventura(Canary Islands) consists of 18 species and 13 unidentified larval specimens. The collection is particularly interesting because the use of modern closing nets and depth monitoring gear has thrown new light on the depth distribution of some of the cephalopod species concerned. Diurnal migration is described for several oceanic cephalopods for the first time.

Mytilus edulis absorbs radioactive ‘ soluble’ iron from citrated sea water either directly or via adsorption on to the mucus used in feeding. The adsorption slows or ceases after 3—7 days when the total iron uptake is about I % of the total body content. In order of decreasing radioactivity, iron is absorbed into the byssus threads, renal organ, digestive gland, gut epithelia, gills, walls of heart and blood sinuses and gonadial and muscular tissues.

The general biology of Leptomysis gracilis (G. O. Sars) and L. lingvura (G. O. Sars) is described. There are three main generations of L. gracilis, spring, summer and autumn ones, produced during the year, although breeding is continuous in the population between the most productive periods. Females carry as many as sixty young in the spring and summer but usually less than twenty in the winter months.

An investigation has been made of the occurrence of 25 amino acids in the hydrolysates of five species of diatoms which had been grown in Erd-Schreiber medium. Their distribution pattern in general resembles that found in other species. However, there are characteristic differences; thus, they contain more serine and 2-amino iso-butyric acid than the other species of phytoplankton.

Total phosphorus and total nitrogen excreted by freshly-caught Calanus finmarchicus (Gunnerus) and C. helgolandicus (Claus) collected from the Clyde and Plymouth Sound have been measured during spring, summer and autumn. The quantities of phosphorus and nitrogen present in animals, plant foods and faecal pellets have also been determined.

The adults ofNereis fucata (Savigny) are commensal with hermit crabs and live within the upper whorls of the shells of their hosts. The mechanism of host adoption has been examined in juveniles reared in the laboratory. There are two distinct phases in their response to their host. The first is a searching phase during which the anterior two-thirds of the worm is extended from the tube and makes wide sweeping movements in its immediate vicinity. This phase can be initiated in the laboratory solely by vibrations in the substrate; the presence of a hermit crab is not required. The second phase begins as soon as a suitable gastropod shell is touched, when the worm immediately leaves its tube and enters the shell. In the laboratory this phase can be achieved without the presence of a hermit crab, so that it is presumably primarily dependent upon the tactile stimuli received from the surface of the shell. It is argued that in nature only hermit-crab shells would commonly give this combination of stimuli to the worm and that the association betweenNereis fucata and hermit crabs is not accidental but commensal.

An investigation of spontaneous bioluminescence as related to sonic-scattering layers was undertaken off Fuerteventura, in the Canary Islands. The apparatus used is described. A definite increase in the magnitude of luminescence at scattering-layer depths is demonstrated. It is shown that the amount of luminescence forward of, and in the net of an Isaacs-Kidd trawl, is very much greater than that either above or below it. A frequency is disclosed within a single flash, and it is hypothesized that this may be a specific property.

Parasites occurred on Erythrops serrata (G. O. Sars) and E. elegans (G. O. Sars) caught in the Clyde sea area and were identified tentatively as species of Thalassomyces, belonging to the Ellobiopsidae (Mauchline, 1968). Wim Vader of the Biological Station, Espegrend, Norway, however, on seeing the drawing of the parasite published by me pointed out that it was more probably a species of choniostomatid copepod. The parasites have now been re-examined and compared with Hansen's (1897) descriptions of these copepods.

The new species Halosphaera parkeae (Prasinophyceae) is described from material collected in the western English Channel. The microscopical structure of the outer wall of the non-motile phase is described and two types of punctation are demonstrated. A general account of the cytology of the mature non-motile phase and of the motile cell is given. Electron micrographs of the scales of the motile cell are compared with those of other species of the genus where known. Buoyancy, size and reproduction are discussed and a number of new taxonomic characters emphasized. The occurence in the same areas of a second type very similar but smaller in size is recorded and the authors have named this form Halosphaera parkeae forma minuta.

The primary productivity of an area of inshore sea in the South Orkney Islands was measured using in situ techniques in two consecutive seasons. Liberation of extracellular products of photosynthesis occurred, accounting for about 1 % of the total carbon fixed at the depth of maximum photosynthesis but rising to 38 % or more when photosynthesis was inhibited at high light intensities.

The authors examined more than 900 thick-lipped grey mullet, Crenimugil labrosus (Risso), from 23 different localities on the Irish coast. The fish ranged in size from fry 1·5—2·0 cm long to adults of up to 58·5 cm long. The scales of mullet show annuli but, with growth, the innermost annuli on the scales become obscured.

Analysis of grab samples from the shallow-water sand community (0—6 m) in the northern Irish Sea has shown that there is an increase in the diversity and in the abundance of amphipod species westwards. The most frequently occurring and the over-all dominant species is Bathyporeia elegans. Six indicator species (Ampelisca brevicornis, Bathyporeia guilliamsoniana, B. elegans, B. nana, Perioculodes longimanus and Pontocrates arenarius) with a high degree of association are present in varying proportions throughout the community.

Introduction

Monthly samples of Argentina sphyraena L. taken in the Clyde Sea Area over 2 years were used to describe age, growth, length-weight relationship, annual cycle in condition, and mortality. Results indicate that one transparent ring is laid down in the otoliths each year between November and May, providing a means of ageing this species.

Vitellogenesis in S. borealis is described. The large protein yolk spheres consist of protein and lipoid. This comes by pinocytosis from outside the oöcyte and from the golgi within the oöcyte. This is discussed in relation to other animal oöcytes. Cortical granules are present at the periphery of the oöcyte and release their contents just before the egg leaves the coelom. When released the eggs have an envelope around them, and evidence is presented which suggests that it is formed from material produced by secretory cells around the exit hole and along the ciliated groove.

Descriptive work carried out in two localities at Port Erin, Isle of Man and three localities at Lough Ine, County Cork has shown that there were marked morpho-logical and anatomical differences between sporophytes of Saccorhiza polyschides (Lightf.) Batt. living in different habitats. The plants developed broad, flimsy, curved, non-digitate blades in areas of weak current; long, tough, flat, very digitate blades in strong current and short, tough, flat blades with few digits in habitats without current, but subject to wave action. By means of culture techniques in the laboratory and transplant experiments in the sea the variations were shown to be phenotypically based. The transferred plants adopted the morphology of the population into which they were moved.

Long-term growth experiments and experiments using 15 as tracer show that extracellular nitrogen liberated by the blue-green alga Calothrix scopulorum is removed from solution by a variety of algae, fungi and bacteria. Active and passive processes are involved in the uptake, the relative importance of each process varying with the test organism and the extracellular products.