Two earlier papers (Wilson, 1968 a, b) have described the rearing of Sabellaria alveolata (L.) and the settlement behaviour of the larvae. It was thought that some of the questions remaining unanswered might be resolved for the cost of one more rearing to obtain the crawling stages needed. With this end in view adult worms were collected at Duckpool on 12 July 1968 during the lowest day-time spring tide of that month. The worms were found to be spawning and had already shed about half of their genital products. On returning to the laboratory a fertilization was made immediately, using a mixture of ova from many females and a mixture of sperms from several males. This fertilization, made at 8 p.m. a few hours after leaving the shore, is the basis of most of the work described in this paper.

In the Plymouth area Sabellaria spinulosa Leuckart is common on stones and shells below low tide mark in the Sound and on outside dredging and trawling grounds. It is often found on living Pecten maximus, much more rarely on Chlamys opercularis, and it is frequent on shells of Buccinum undatum, especially those inhabited by hermit crabs. Several tubes may be found close together, sometimes in contact, but it does not form massive colonies as it does on some shores bordering the North Sea and in deeper water of that region (McIntosh, 1922, pp. 14, 20). It is a smaller species than S. alveolata (L.) and its tubes, built mostly of mineral grains, are harder and stronger than those of the latter. At Plymouth the tubes attached to Pecten shells are usually larger, stronger, and include bigger grains, and are cleaner than are those on stones dredged in the Sound. Empty tubes are common, especially on stones and loose shells, and such tubes are sometimes tennanted by other worms.

Spirula spirula has stimulated considerable interest since it was first discovered.

It is a member of one of the two genera of sepioids to frequent oceanic water (the other being Heteroteuthis); it has a unique spiral shell which acts as a buoyancy mechanism and can withstand considerable pressure (Denton, Gilpin-Brown & Howarth, 1967); and, until the capture by the Danish Oceanographical expeditions it was considered very rare, only 12 specimens having been captured. The Dana expeditions caught 193 individuals from 1909 to 1931 and these were described by Kerr (1931) and Bruun (1943,1955). Most of these were caught in the waters around the Canary Islands of the North Atlantic. Bruun (1943) arranged the specimens according to month and size and claimed that two size groups could be distinguished. The specimens were taken over a wide geographical area, in several years and during the months of February (1 specimen), March (40), April (3), May (8), June (1), August (1) and October (23). His conclusion concerning growth depends entirely upon his decision to split the March sample into two year-groups; those above 1.9 cm in ventral mantle length he put in a separate year-class to those below 1.9 cm in ventral mantle length. This division was arbitrary and, one suspects, based on a belief that a one-year life-span was likely.

Clearly the growth of Spirula requires further study based on a larger collection and the present paper is an attempt to fulfil this need.

MATERIAL AND METHODS

This work is based upon 256 specimens collected to the south-east of Fuerteventura in the Canary Islands by R.R.S. ‘Discovery’ during 1965–68.

One of the major advances made in the development of media for the culture of marine phytoplankton was the introduction of chelating agents as a means of controlling the concentrations of the trace metals necessary for plant growth; an excellent historical survey of this field has been provided by Provasoli, McLaughlin and Droop (1957). Much of the discussion concerning the role of the chelating agents has centred upon the maintenance of the iron in solution at concentrations adequate for plant nutrition (Droop, 1961; Provasoli, 1963; Johnston, 1964). In the absence of chelators, the pH of the culture media would result in almost complete precipitation of the iron.

Present knowledge of the nutritional requirements of fish is limited to certain species of salmon and trout (e.g. Halver, DeLong & Mertz, 1957; Shanks, Gahimer & Halver, 1962). In view of the current interest in the cultivation of marine flatfish (Shelbourne, 1964) information on their dietary needs is equally desirable. Experience with salmon (DeLong, Halver & Mertz, 1958) has indicated that protein is the largest and most expensive constituent of fish diets and studies on the nutritional value of different food proteins for fish are necessary if the fish are to be reared economically and successfully. A desirable prerequisite to such studies is a knowledge of those amino acids for which the fish has an absolute dietary requirement, i.e. which it cannot itself synthesize from other substances normally available. With most animals these requirements have been identified by growth trials using partially (or wholly) defined diets. The rearing of fish on defined diets is not easy and it seemed in the first instance that an indirect but valid approach might be utilized. If animals are given a radioactively labelled carbon source, such as uniformly labelled [U-14C]glucose a significant amount of the radioactive carbon will be incorporated only into those compounds which the animal can itself synthesize. By isolating the amino acids from the tissue proteins following such a dose the essential amino acids are identified as those which are not radioactive. The amino acids containing radioactivity correspond with the so-called non-essential amino acids.

A net sample of phytoplankton taken in the outer Moray Firth in which there were many cells of R. hebetata forma semispina and several cells of R. hebetata forma hiemalis (Fig. 1 a, b) was also found to contain cells either with one forma semispina calyptra or one forma hiemalis calyptra, in which the cell wall changed abruptly at the opposite end to a thin weakly silicified, sometimes almost membranous structure, ending in a central, broadly conical apex with a delicate hollow spine (Fig. 2j, k). The perizonium like appearance of one end of these cells suggested that they might be a stage in the development of the auxospore in R. hebetata Bailey (sensu Gran).

The podocyst is a cuticular patella-shaped stage in the life-cycle of certain scyphopolyps and has been described recently (Chapman, 1968) from the standpoint of anatomy, histochemistry and development. New material has come to hand necessitating a reassessment of the views concerning the formation of this deceptively simple structure.

During studies on the biology of young plaice (P. platessa L.) in Manx waters an experiment was begun in August 1965 to determine the efficiency of food conversion of O-group plaice. The experiment was repeated in a slightly modified form in August 1966. The objects of these investigations were to determine the weight of chopped mussel required by O-group plaice to increase their body weight by 1 g and to show whether the efficiency of conversion varied with changes in the water temperature and with the quantities of the particular type of food that were supplied to the plaice.

Investigations on the digestive enzymes of polychaetes have, in most cases, been limited to the presence or absence of protein (gelatin) digesting and starch digesting enzymes. These enzymes have been shown to be present in all the polychaetes that have been studied (Mansour-Bek, 1954; Dales, 1955; Marsden, 1963). The results for the lugworm, Arenicola marina (L.) have been varied. Recent work has indicated the presence of enzymes capable of digesting starch and gelatin in the oesophagus, oesophageal pouches and the stomach of the lugworm (Kermack, 1955). However, Brasil (1903) found that no digestion took place when secreted fluids of the oesophageal pouches were incubated with starch, though fibrin was digested both by these fluids and a water extract of the ‘caeca’. Nicol (1930) records the work of Krukenberg, who found that proteolytic enzymes were present in the gut of A. marina. Kermack (1955) noted that the stomach was slightly acidic, though Nicol (1930) records the work of Wirèn, who found that the contents of the ‘intestine’ and the ‘intestinal caeca’ of A. marina were alkaline. As there have been no detailed analyses of the digestive enzymes of the lugworm, a survey of the distribution of carbohydrases, proteases and lipases in the gut of A. marina was carried out, and the optimal range of the carbohydrases investigated.

Although nematodes form the dominant meiofaunal group in almost all marine sediments, ecological investigations have been confined mainly to littoral or shallow water habitats. Among these studies may be included those of Wieser (1959), Gerlach (1953, 1954), Capstick (1959), King (1962), Rie-mann (1966) and Hopper & Meyers (1967). The qualitative distribution of the nematode fauna of various types of substrates in Kiel Bay and from the Chilean Coast have been discussed by Gerlach (1958) and Wieser (1959a). The only work which contains both qualitative and quantitative data from offshore substrates is that of Wieser (1960), which concerns the shallow sediments (12–30 m) in Buzzards Bay, Massachusetts, and contains a review of the purely quantitative results of previous authors.

The copepod Asellopsis intermedia (T. Scott) is a conspicuous member of the meiobenthos in sand on a small exposed beach at Firemore, in Loch Ewe, Scotland, and is the only species of this genus so far recorded interridally from the area. Length of adults does not exceed 0.65 mm in females and 0.55 mm in males. Although it lives below the sand surface, it is not an interstitial form since it burrows by displacing the sand grains rather than by moving freely in the interstitial spaces.

It has been argued (McLaren, 1963, 1965) that reproduction and development of copepods may be physiologically (rather than trophically) determined when food is sufficiently abundant: thus, under these conditions the rates of development and egg production, and the total number of eggs laid by a female in her lifetime vary only with the physical factors of the environment such as temperature, salinity and pressure, temperature being by far the most important. This paper is part of a continuing study of the physiological controls of growth and development as part of a general investigation on productivity of marine zooplankton.

Schistomysis ornata (G. O. Sars) occurs in the deeper regions of the Firth of Clyde and in many of the lochs of the west coast of Scotland. It has been caught in Loch Fyne at depths as great as 175 m but is more common living above a muddy bottom in depths between 50 and 100 m. It is rarely caught in large numbers but as many as 100 individuals have been caught per haul in the western arm of the Kyles of Bute, Firth of Clyde and in Loch Etive, Argyll. It is associated with populations of Erythrops serrata (G. O. Sars) and Leptomysisgracilis (G.O. Sars) in the Clyde (Mauchline, 1968,1969) and with populations of Pareuchaeta norvegica (Boeck) and Sagitta elegans Verrill in Loch Etive.

The study of diurnal vertical movements of macro-plankton (Russell, 1925) showed that many organisms, including amphipods migrated to the surface of the sea at night. Since this work there have been several papers reporting vertical movements in intertidal waters. Elmhirst (1931), demonstrated that certain species of amphipod swam in the surf zone during the night and that they showed seasonal variations in numbers, with a spring maximum. Subsequently, Watkin (1939, 1941) distinguished between those in-faunal species performing nocturnal vertical migrations into the surf and tidal immigrants carried in from sub-littoral habitats by the tide.

Platymonas convolutae Parke et Manton is the natural algal partner of the symbiotic worm Convoluta roscoffensis Graff (Parke & Manton 1967). Recent work by Provasoli, Yamasu & Manton (1968) has shown that although several algae can form a symbiotic relationship with the worm if supplied in unialgal culture, the natural symbiont is the most effective and is able to eliminate competitors. The alga can be cultured in a denned medium away from its partner, and this paper presents some physiological characteristics of the alga in pure culture in comparison with some of its free-living relatives, in particular the type species of the genus Platymonas, P. tetrathele G. S. West. The present investigation has been concerned mainly with the uptake of carbohydrates and the utilization of organic nitrogen. Other aspects that are included are the excretion of metabolites into the medium and the soluble carbohydrates found within the algae. In addition, culturing the algae has revealed a difference in behaviour of possible relevance to the symbiotic relationship.

The first specimens of Rhabdopleura to be found were dredged by G.O. Sars from a depth of 120 fm (220 m) at Skraaven (Fig. 1) in the Lofoten Islands during 1866. They were mentioned in a fauna list by M. Sars (1868) as Halilophus mirabilis, and fully described by G.O. Sars (1872, 1874) as Rhabdopleura mirabilis. By that date AUman (1869 a-c) had described Rhabdopleura normani. His specimens had been dredged from 90 fm (165 m) off the Shetland Islands in 1868 by A. M. Norman and J. G. Jeffreys. Burdon-Jones (1954) gives the locality more precisely as:lsquo;… a depth of 93 fm at a point in the outer Haaf, some 40 miles east of Whalsey Skerries’ (Fig. 1). In 1880 Hincks described a third species which he named R. compacta because of its distinctive habit of growth. The habitat and locality were somewhat inadequately given as: ‘On shells from deep water; Coast of Antrim’ (Fig. 1). Hincks makes acknowledgement to Hyndman for dredging these shells (Hincks, 1880). From 1857 to 1859 Hyndman was serving on the Belfast Dredging Committee and it is possible that the specimens of R. compacta, which Hincks had discovered in material sent to him by Hyndman many years previously, were among the polyzoan collections known to have been made off the coast of Antrim. Hyndman (1858) included a list of polyzoa identified by Hincks, from deep water near the Maidens' Rocks. The following year Hyndman (1859) included a further list of polyzoa identified by Hincks, for which specific localities are not given.

In Balanus balanoides (L.) several abrupt physiological changes occur after the breeding season in November. They include loss of gonads and associated organs, the acquisition of a high degree of cold tolerance (Crisp & Ritz, 1967), interruption of the regular sequence of moulting cycles (Crisp & Patel, 1960) and the reduction in feeding activity.

The cosmopolitan genus Orchestia is divisible into two ecological groups: littoral and terrestrial, as denned by Hurley (1959). Only littoral species are known from Britain and three which occur in the Medway estuary have been studied. O. gammarella (Pallas) and O. mediterranea A. Costa are marine or estuarine, the former being found above the recent high water mark under wrack or stones and the latter below this level under stones. O. cavimana Heller is a freshwater species, extending into the oligohalinicum of estuaries (Den Hartog, 1963), which is found near the wrack line. During a study of the biology of these species possible mechanisms which control the tidal levels occupied on the shore were investigated, including the temporal characteristics of locomotory activity.

It has been known for a long time that the commonest British sea anemone, Actinia equina L., incubates its young in the gastric cavity (Dalyell, 1848).