After initial trials a technique was devised which made it possible to rear about 12 % of newly hatched larvae of the pilchard Sardina pilchardus (Walbaum) to a point well beyond the yolk-sac stage. A survival rate of this order was considered quite satisfactory for larvae which are so small at hatching.

Two hydrographic cruises have been carried out in the Irish Sea during the winters of 1965 and 1966. It has been found that near the Welsh Coast reactive silicate concentrations were remarkably constant and lower than expected. In contrast, near the Irish coast there were marked variations in reactive silicate concentrations and the values found were considerably higher than those for the Welsh coast.

Methods of filtration and storage of sea-water samples intended for silicate analysis have been investigated. The desirability in some circumstances of filtering water samples before analysis has been demonstrated. The behaviour of three recommended methods for the analysis of silicate in sea water has been compared by inter-calibration studies.

Details are given of the nets used and the sampling procedures adopted to investigate patterns of vertical distribution in an oceanic pelagic fauna. Ancillary gear and laboratory methods are described. The paper concludes with a discussion of the limitations of the sampling.

The mean weight in sea water of specimens of the electric ray, Torpedo nobiliana Bonaarte, was only 0·4 % of the weight in air compared with 4·4 % in other bottom-living rays. T. nobiliana was so buoyant because it had large livers (up to 20% by weight) containing a lot (up to 70 %) of oil of low density (0·91 g/cm3) and because some of the body tissues were less dense than in other rays.

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.

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.

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.

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.

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.

The structure of the tentacular crown in a multitentaculate pogonophoran, Siphonobrachia ilyophora Nielsen, has been examined by light and electron microscopy. The fine structural organization of the tentacles is described and discussed in relation to the suggested functions for the tentacles in Pogonophora.

Pseudocalanus elongatus(Boeck) from Plymouth Station Ex was kept in reproducing culture for 6 months and approximately four generations. Cultured adult females were at least as large as wild females of the same species which havematured at a comparable temperature (15 °C) in nature. At 15 °C hatching time was 2—3 days, time to first copepodite was 18—20 days, and the time from egg to development of an egg-carrying female averaged 37 days.

The estuary of the Tamar has been surveyed from March to September 1968. Salinity distributions and variations have been measured with the object of providing a preliminary picture of the general circulation. Tidal flows appear to have most effect on water movement in the estuary.

Idotea metallica Bosc is a dark-brown or blue-black species, its colour being controlled largely by the degree of expansion of, and pigment concentration in, the dermal chromatophores. In addition, the iridophores produce the characteristic metallic sheen by Tyndall scattering.

The original descriptions of species of the genus Ptychodiscus are discussed. Recent material is examined both alive and preserved. It is concluded that the only valid species is Ptychodiscus noctiluca Stein. Ptychodiscus carinatus Kofoid, P. inflatus Pavillard and Diplocystis antarctica Cleve are all synonymous with this species.

Reproduction and feeding of Argentina sphyraena L. were investigated during a study of the biology of this species in the Clyde Sea Area of Western Scotland from 1963 to 1966.

Deposit-feeding by Scrobicularia planaScrobiculariaplana (Da Costa) along the mud surface occurs throughout the period of low tide if the water table remains at the surface. The rate of deposit-feeding is unaffected by the time after emersion at low tide except where excessive drainage prevents feeding along the mud surface, in which case it is possible that animals feed from the sides of their burrows at or below the level of the water table.