Between May 1961 and November 1970 almost monthly visits were made to Duckpool, an exposed shore on the north coast of Cornwall, where Sabellaria alveolata (L.) is the dominant organism on low-level rocks uncovered only by spring tides. Massive colonies several feet across and up to some 2 ft thick, formed mainly of shell particles cemented together by the worms, as well as many smaller colonies and single tubes, here reach their maximum development in south-west England.

Selected sites and colonies were photographed and some measured at frequent intervals over long periods of time. comparative studies of long series of colour transparencies examined closely with a binocular microscope have proved invaluable in elucidating the manner and rate of growth of varied types of colonies, their lengths of life and the manner of their ultimate destruction. Detailed histories of these selected colonies are given in this paper and reveal much that was previously unknown or only guessed.

A short spawning period every year in July initiates each new generation. Experimental work, already published, had shown that individuals develop at different rates, the final stage with ability to settle being reached at any time from 6 weeks to 6 or more months, and when reached the ability can be retained for some weeks. This accords with observations on the shore, where settlement takes place in any month between late August and the following early May, or rarely June. The intensity of settlement varies enormously from year to year, there being none in some years, with slight or moderate or heavy settlements in others.

Proximate analyses of deep-frozen samples of Euphausia superba Dana obtained in December and January showed that protein was the major constituent, averaging just over 50% of the dry body weight. Lipid was much more variable; extreme limits of variation were from 6 to 33% dry weight, though the lipid content during January was distinctly higher than in December (means 27 and 13% dry weight respectively). This increase probably reflects a more intensive grazing by krill during the Antarctic summer. Increased lipid appears to be associated with some reduction in water content and in ash. Carbohydrate is low, the mean value for December being just under 5% dry body weight, but the content is slightly higher than that found for most zooplankton and may reflect the herbivorous habit of E. superba. The proximate biochemical composition of krill is similar to that of the boreal euphausiid, Meganyctiphanes norvegica.

Seventy-two holdfast samples of the kelp Laminaria hyperborea (Gunn.) Fosl., from fifteen approximately equidistant sites along the North-East coast of Britain, from St Abbs in Berwickshire to Flamborough Head, have been taken during the course of one spring-tide period. The nematode fauna of these samples (20,744 specimens of 61 species) has been examined and the data are presented in such a way as to facilitate comparison with previous work. The fauna in the North Sea is dominated by large enoploid species. Enoplus communis Bastian, Anticoma acuminata (Eberth), Thoracostoma coronatum (Eberth), Phanoderma albidum Bastian and Pontonema vulgaris (Bastian) are regularly abundant. The minor contribution of the family Monohysteridae indicates that silt is of little importance to the nematode fauna in exposed localities. The holdfast-dwelling nematodes are generally epigrowth feeders or omnivores, the latter exploiting the sediment-feeding niche apparently unavailable to specialized deposit feeders. Species with short body setae, body length above 1·5 mm, having smooth cuticles and possessing some visual mechanism are dominant. It is upheld that algal structure per se is of primary importance in determining the different nematode communities found to exist in algae of different growth forms, and to account for the similarity shown between the faunas inhabiting similar algal growth forms from widely separate geographical areas and differing levels on the shore. It is suggested that habitat-component generic keys might facilitate investigation of unknown regions.

The reproductive cycles of the two cockles Cerastoderma edule (L.) and C.glaucum (Poiret) (= Cardium lamarcki Reeve) from a mixed population in the Crouch estuary, Essex, have been investigated. Reproductive maturity was estimated by assessment of gonad condition. A difference in maturity related to shore level was noted. The reproductive cycles of the two cockles were found to be essentially similar. Rapid gametogenesis occurred in both cockles in spring, C. edule then spawned in May, whereas C. glaucum did not spawn until July. The difference in time of spawning appears to be responsible for the maintenance of the two genotypes in a sympatric association, as hybridization experiments showed an absence of isolation at the gamete level. The relationship between C. edule and C. glaucum is discussed.

The formation of ‘teeth’ in immature Nucella lapillus (L.) is indicative of a stoppage in growth. Along the western coasts of southern Britain the proportion of individuals showing these growth disturbances is predictably related to the exposure of the shore to wave action. Farther east the proportion is much higher but not obviously so related. Sharp discontinuities separate eastern and western populations. Possible reasons for the differences are discussed and it is concluded that great care must be exercised when applying information about this species derived from the one coast to situations on the other. The potential value of this species as an indicator of environmental change is considered.

The biology of Praunus flexuosus (Müller) is closely similar to that of P. neglectus (G. O. Sars). In both species the over-wintering population matures and breeds in the early spring and summer to produce a spring generation of young which are evident in the population in May or June. The members of the over-wintering population die off in July or August. Some members of the spring generation become sexually mature and breed in the early autumn. The progeny of this autumn breeding, along with the bulk of the spring generation, form the over-wintering population. These species are omnivorous feeding on animal and plant debris and also preying on small crustaceans, very frequently harpacticid copepods. The maximum brood size found in P. flexuosus was 63 and in P. neglectus was 81. The biology of the populations on the west coast of Scotland is briefly compared with that of populations in Port Erin, Isle of Man, in Norway and at Roscoff.

Schistomysis kervillei (G. O. Sars) is a common species in Loch Ewe, Gairloch and Gruinard Bay in north-west Scotland and a rare species in the Firth of Clyde. It breeds throughout the year but most intensely in the spring and summer, to produce a spring and summer generation of young. The maximum number of young found in a marsupium was 47. The species is omnivorous. Its biology is briefly compared with that of S. spiritus (Norman) and S. ornata (G. O. Sars).

A micro-analytical scheme for the determination of protein, total carbohydrate, freereducing substances, total lipid, phospholipid and RNA levels in marine invertebrate larvae is described and discussed. The scheme is designed for use with 1–2 mg dry weight of tissue. Values of 171·0, 15·03, 50·4 and 11·58 μg/mg dry weight of larvae (flesh + shell) are given for the levels of protein, total carbohydrate, total lipid and RNA respectively, in newly released larvae of Ostrea edulis L.

An examination of the postlarvae of the goby Lebetus Winther collected in the neighbourhood of Plymouth shows that there are two forms, separable on degree of development of the fins, meristic characters and body proportions. The differences are sufficient to indicate that there must be two species whose identity can only be made certain by rearing, since the original two species L. orca (Collett) and L. scorpioides (Collett) have recently been regarded as one species showing sexual dimorphism.

Determinations have been made, by neutron activation analysis, of the concentrations of tantalum in the tissues of some common crustaceans, molluscs, echinoderms and tunicates of coastal waters of southern England. The concentrations ranged from less than 0·01 ppm dry weight in the muscle of Mytilus edulis to 2 ppm dry weight in Neomysis integer. Two ascidian species showed concentrations of about 0·2 ppm dry weight in the whole organism. The measurements support the generalised concentration factors which have previously been assumed in assessing the radiobiological significance of discharges of radioactive tantalum to the marine environment.

The original descriptions of these two species are discussed and the material mentioned in Smith's description is examined. Discrepancies between Smith's description of Coscinodiscus concinnus and the present interpretation of this species are pointed out. Ways of typifying the two species so as to preserve current usage and still fulfil the requirement of the International Code of Botanical Nomenclature are given. Lectotypes for the two species are designated. Diagnostic characters distinguishing the two species in the living state as well as the cleaned valves are given.

The distribution of the larvae of four of the five species of Ammodytidae occurring in Scottish waters is examined. The two most abundant species, Ammodytes marinus Raitt and Gymnammodytes semisquamatus (Jourdain) are described in detail and their abundance recorded. A. marinus larvae were found throughout the survey area, but were most abundant in the Moray Firth and around Orkney. G. semisquamatus larvae were most abundant along the north and west coasts, although they were recorded in a few areas off the east coast of Scotland. A. lanceolatus Lesauvage larvae occurred generally in Scottish waters, although few larvae were caught. A. immaculatus Corbin larvae, which have not previously been recorded in the Scottish area, were also rare and were restricted to areas off the north and west coasts. The material was not suitable for demonstrating the distribution of larvae of A. lancea Raitt. The occurrence of larvae is related to the spawning season of each species.

The population dynamics of the mysid crustacean Praunus flexuosus have been studied at Ardmaddy Bay, Loch Etive. A salinity tolerance range of 2–33‰ has been demonstrated, over which the body tissues experience the range 11–28‰. Comparison is made between the osmoregulatory capacity of Praunus flexuosus and the closely related Neomysis integer.

A saline pond known as the ‘Salts Hole’ at Holkham on the north coast of Norfolk is situated between the pine-covered sand-hills and the fields that have been reclaimed for agriculture from pre-existing salt-marshes. It has a salinity of about 75% of that of sea water and supports a peculiar relict marine fauna. Except for the rare occurrence of flooding for a short period, as in the great storm of 1953, the pond has probably been cut off from the sea for about 250 years. It presents three problems: how it got its fauna and flora; how its marine character is maintained; and how the pond originated geographically. The fauna and flora, as described, show the pond as a refuge where various marine and brackish species have managed to maintain themselves and co-exist in water outside their normal and differing ranges of salinity. The main character of the pond is kept remarkably constant with respect to salinity, alkalinity, temperature and oxygenation. The pond is a study in ‘natural engineering’, constituting a natural marine aquarium with natural controls. It is fed near the level of high-water neap tide by continuous flow from a salt spring of very constant salinity supplied from water contained in the extensive coastal sands. Its only apparent artificial feature is the outlet controlled by a dam through a culvert into a ditch that conveys its water through the fields to the sea at Wells nearly two miles away. Search in the muniment room at Holkham Hall brought to light maps dating back to Elizabethan days which show the history of the Salts Hole.