The interstitial meiofauna was investigated on an exposed sand beach at Whitsand Bay, Cornwall. An intertidal transect of eight stations was sampled regularly over a period of 2 years from May 1968 to May 1970. Quantitative core samples were taken to a depth of 50 cm. Nematodes were the dominant group on the beach, forming about 50% of the meiofauna. Harpacticoid copepods were second in overall abundance. Hydrozoa, turbellaria, gastrotrichs and tardigrades were also present.

Planktomya henseni Simroth 1896 is a pelagic bivalve widely distributed throughout the warm-temperate and tropical North and South Atlantic Ocean. It is also known from a single collection in the tropical Pacific Ocean. The geographical distribution of Planktomya is probably circumtropical.

An investigation into the natural regime of coastal suspended solids before discharge of potash mining waste is described. Regular samples of suspended material were taken over the period September 1968 to August 1970. Statistical analyses showed significant differences in suspended solid values between the months and between inshore and offshore sampling stations. There was no significant difference between sampling points along the coast. The inshore suspended solid values were low from May to September. At other months and at the offshore stations there was a gradual change from summer (low) to winter (high) values and vice versa.

Sea temperature, sea state, tidal range and river flow correlated significantly with suspended solid values. It is suggested that wave action, tidal currents and river flow control most of the variation in load of suspended matter off the N. Yorkshire coast. The significant negative correlation between temperature and suspended solid values is not regarded as a causal relationship. Low temperatures are associated with high wave activity and high river flow rates; factors which are more likely to have a causal relationship with suspended solid loads than temperature. Thus, suspended matter variations off the Yorkshire coast are probably determined by physical rather than biological temperature-dependent processes.

From multiple linear regression analyses, sea state, tidal range and river flow were found to account for 64·1% of the variation of the inshore suspended solid values and 52·4% of the variation of offshore values. Using the multiple regression equations as mathematical models it was possible to derive accurate predictions of the natural suspended solid load.

Culture studies on the morphology, development and, in some cases, on the life-histories of green shell-boring algae, have shown that in Britain there are at least six species which could be confused under the name Gomontia polyrhiza Born, et Flah. Of these six species it has been possible to identify only four, namely Eugomontia sacculata and Entocladia perforans and Codiolum stages in the life-histories of Codiolum polyrhizum and Monostroma grevillei. The possibility that there are as yet unidentified life-histories involving more shell-boring Codiolum stages has been suggested.

The vertical and horizontal distribution on the shore and the distribution between the host shell species, is described for a number of species of green shell-boring algae. A list is given of the records made in Britain for shell-boring Codiolum stages and for Entocladia perforans. An account is given of the sequence in which shell-boring algae attack Spirorbis worm tubes in the Isle of Man.

The external morphology of eight species of Choanoflagellates representing eight genera have been investigated with an electron microscope. These include one new species (Acanthoecopsis apoda). Sections have been obtained of Monosiga ovata, a species without a lorica. All the other species possess loricas with very regular and precise distinguishing features when seen in shadowcast whole mounts. The position of the group is discussed in a preliminary way in the light of fine structure.

Palaemon elegans Rathke on South Wales coasts, unlike P. serratus (Pennant), does not migrate offshore in winter but stays in intertidal pools throughout the year. Both species occur in rock pools in summer, with P. elegans extending farthest up the shore and often occurring in pools above M.H.W.N. Each shows a spontaneous but short-lived tidal rhythm of locomotor activity in constant laboratory conditions, the rhythm persisting longer in isolated prawns than in groups of animals recorded together. Peak activity occurred on the ‘expected’ ebb, and light/dark changes, including those associated with tidal rise and fall, appear to be important in synchronizing the rhythm. The tidal rhythm of Palaemon elegans above M.H.W.N. quickly rephases to a semi-diurnal dusk/dark rhythm during the period of neap tides, the rhythm again becoming tidal when spring tides return. The possible significance of ebb activity is discussed.

Three species of medusae of the genus Podocoryne M. Sars have been collected in the Clyde Sea Area: P. hartlaubi Neppi & Stiasny, P. borealis (Mayer) and P. camea M. Sars. Their hydroids have also been found there, and medusae liberated in the laboratory have been reared to maturity. Detailed illustrated accounts of the hydroids and of the developmental stages of the medusae are given.

The hydroid of P. hartlaubi proves to be identical with the hydroid Podocoryne areolata (Alder), a species long known to liberate medusae, which however have not previously been referred with certainty to any known species of medusa. By priority the name P. areolata has seniority over P. hartlaubi and applies to both hydroid and medusa. The hydroid P. hartlaubi reported from Naples by Yamada is discussed, and is considered to be identical with P. areolata. In the Clyde Sea Area the hydroid has been found only on certain small gastropod shells occupied by hermit-crabs.

The hydroid of P. borealis has hitherto been very inadequately known. The hydroid is very common in the Clyde Sea Area, living on a variety of host animals on muddy grounds. Colonies have also been reared in the laboratory from ripe medusae caught in the sea. Abundant material has accordingly been obtained, making possible a full description of the species.

The diagnostic features of the Ponto-Caspian gobiid genus Knipowitschia Iljin, 1927 and related European genera are summarized with reference to the cephalic lateral-line system. The Adriatic Gobius panizzae Verga, 1841 is now shown to belong to Knipowitschia, and a second species, K. caucasica (Kawrajsky, in Berg, 1916), widespread in the Ponto-Caspian region, is recorded from the northern Adriatic (Gulf of Venice). The occurrence of these species in the Adriatic Sea is explained by Quaternary changes in union between the Mediterranean and Black Sea, with K. panizzae derived from Black Sea Knipowitschia stock emigrating via a temporary Riss/Würm interglacial confluence, and the K. caucasica of very recent origin through the existing postglacial connexion. A redescription of K. panizzae, based on syntypes and more recent material, is provided in an Appendix.

The velum of Lacuna vincta (Montagu) and Nassarius incrassatus (Ström) is retracted into the shell by 2 dorsal and 2 ventral groups of muscles, bilaterally arranged, which are components of the larval retractor muscle. Each dorsal group passes forward from its area of origin on the shell to the dorsal part of the head where some fibres insert and adjacent ones enter the velar fold. The velum is bilobed in Lacuna and the muscles radiate through the dorsal half of the lobe to insert on the anterior and posterior surfaces and ciliated edge, whereas Nassarius has 4 long velar lobes, 2 dorsal and 2 ventral, and the muscles form a median bundle from which fibres radiate to similar insertions. Each ventral group of muscles passes through the nerve ring lateral to the developing radular sac in Lacuna and to the developing proboscis in Nassarius, and muscles accompanying them insert on the sac and proboscis wall. Anterior to the ring some muscles insert on the lips and the buccal wall posterior to the oral sphincter and alongside attachments of muscles from the foot. The majority pass to the mentum, a median protuberance of the lower lip with non-vibratile cilia, where right and left ventral cephalic retractors and muscles from the foot converge. The pedal muscles attach here and from this area muscles radiate to multiple insertions on the head and ventral half of the velum. This arrangement of the ventral muscles allows the increased angle of mobility required by the ventral areas of the velum in swimming and feeding and the intimate contact between velum and foot.

Analysis of the carotenoid pigment and lipid concentrations of groups of the smaller zooplankton organisms from different depths has suggested a midwater maximum for carotenoid concentrations and a slight depth-related increase in lipid content. Similar analysis of seventeen species of euphausiid has not indicated similar trends, but has shown a close relationship between size and pigment content in all species other than those of Stylocheiron, which have significantly lower pigment concentrations. Comparisons of the data of Fisher, Kon & Thompson (1964) on the pigment and lipid concentrations of copepods with the known depth ranges of the various species have suggested a midwater maximum in pigment concentrations, but no consistent trends in the lipid concentrations. A midwater pigment peak is explicable in terms of pigment accessibility and requirement for protective coloration, and the significance of the pigments is discussed.

Precocious development of sexual reproductive structures (sporosacs) in Cordylophora (Pallas, Allman) occurs when colonies are grown in the absence of a suitable substratum. Neither varying the nature of the substratum provided nor diverse surgical manipulations will induce this morphogenetic modification. Sessile colonies will also initiate sporosac development if ubstrate availability is limited experimentally.

Artemia salina has been reared on unialgal diets of Phaeodactylum tricornutum, Monochrysis lutheri, Platymonas tetrahele and Chlamydomonas sp. In most instances the component fatty-acid distribution of the Artemia bore little resemblance to that of its food. Thus, oleic and stearic acids are relatively enriched in the shrimps, whereas hexadecatetraenoic acid is much depleted. It is suggested that the metabolic requirements of the shrimps is of at least equal importance to the composition of their food in determining the component fatty-acid distribution of their lipids.

The activity of the following planktonic animals has been observed at hydrostatic pressures up to 500 atm: Gigantocypris mülleri, Conchoecia hyalophyllum, C. macrocheira, C. rhynchena, Parathemisto sp., Megacalanus longicornis, Euaugaptilus magna, Pareuchaeta gracilis, Pleuromamma robusta, Anomalocera patersoni, Euphausia krohni, Acanthephyra pelagica and Amalopeus elegans. Respiration of Gigantocypris and Systellaspis debilis was also measured at pressure.

Luidia ciliaris (Philippi) has intraoral digestion and was found to be a selective feeder on echinoderms. In 258 specimens from the Irish Sea, echinoderms occurred in 97·4% of all stomachs containing food and contributed 92% of the food volume (estimated by points method). The most important food items were Psammechinus miliaris, Ophiothrix fragilis, Ophiura albida and Ophiocomina nigra. Ophiocomina nigra did not occur as frequently as would be expected from their availability. Observation in situ revealed that large specimens had efficient escape response to moving Luidia and aquarium experiments showed that O. nigra deprived of their moving ability were readily eaten. However, the Luidia showed clear preference to Ophiothrix fragilis. There was no distinct seasonal difference in the composition of the diet, but a tendency to a minimum feeding activity in May-June, probably connected with the spawning period.

The hydrographic conditions in the two sea-lochs is briefly described where relevant to the survey of the benthos. Seasonal changes in temperature and salinity in Loch Etive appear to follow roughly the local coastal pattern but usually with a lag in timing that is considered to be because of the restricting effect of the twin sills. Replenishment of deep-basin water by ventilation over the sills is spasmodic and controlled by surface stratification; the latter being due primarily to freshwater runoff. This situation contrasts with Loch Creran which has only a small catchment and where the seasonal hydrography closely follows the pattern outside. Other possible reasons for the differences observed between the two lochs are discussed.

The bottom fauna of both lochs was sampled semi-quantitatively with an anchor dredge at 22 stations in Loch Etive and 8 in Loch Creran at depths from 7–117 m. A detailed list of the fully marine fauna present is given. The species occurrences in the single-haul samples are compared objectively using a coefficient of similarity of the presence/absence records. An attempt is made to relate the groupings shown up to the classical ‘bottom community’ concept, to the feeding-type categories of the bottom animals and to analysis of particle size of sediment samples taken at the same stations. A correlation to sediment type was apparent. This is considered to owe as much to local hydrographic conditions which the sediment reflect as to the sediment itself.