Spontaneous rhythmic activity in the lugworm Arenicola marina (L.) is believed to be under control of a pacemaker located in the ventral nerve cord and oesophageal plexus (Wells, 1937). Since the rhythmic component which often dominates the spontaneous behaviour of polychaete worms consists of movements resulting in irrigation of the tube or burrow, and thus ventilation of respiratory surfaces, pacemaker control of the rhythm differs strikingly from reflex control of ventilation in other animals.

The overriding metabolic advantages of aerobic as compared with anaerobic respiration have resulted in its use by the majority of multicellular organisms. However, in some habitats oxygen is limiting to such an extent that anaerobic respiration becomes a necessity for survival. It has frequently been demonstrated that the extent of anaerobiosis depends, obviously, on the degree of oxygenation of the environment (see reviews by von Brand, 1944, 1945; Beadle, 1961). Hence, not only are there entirely anaerobic organisms but many other organisms exist which, in times of anoxic stress, are able to undergo a partial, or facultative, anaerobiosis. Lindeman (1942) discovered that, at low temperature, aquatic chironomid larvae could survive the entire winter anaerobically in the anoxic hypolimnion of freshwater lakes. Similarly, but to a lesser extent, pond-living crayfish of the genus Cambarus are more resistant to low oxygen concentration than stream-living individuals (Park, 1945). Walshe (1948) has also been able to establish a similar relationship in a group of stream and ditch dwelling chironomid larvae.

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 fouling of formerly clean sandy shores by the weathered residues of crude oil is all too familiar. Vigorous use of solvent emulsifiers can restore the beach ‘whiter than white’ but this damages the creatures which normally live in and on the sand. Unless the oil pollution is continual, the beach will usually rid itself of oil aided by waves and tides. Sometimes the disappearance of the oil may amount to no more than its bodily removal elsewhere or its burial out of sight, but inevitably, its ultimate destruction must be as the result of photochemical and biological processes. For intertidal sands where oil may become buried by wave action, the photochemical aspect is perhaps less important than for floating oil and the biological pathway is more important. In the experiments described here an attempt is made to investigate the rate of oil destruction by natural beach micro-organisms. Under the experimental conditions used, it is not difficult to sustain over a period of several months a fairly representative model of a beach with its populations of bacteria, diatoms and interstitial benthic animals.

Only three of the twenty species at present ascribed to the genus Mysidopsis have been recorded around the coasts of Britain; these are M. gibbosa G. O. Sars, M. didelphys Norman and M. angusta G. O. Sars. The latter species is rare and has never been caught in large numbers. Large catches of M. gibbosa are made in certain sandy bays in the Firth of Clyde and the species is quite common in Gaineamh Smuagh, a sandy bay in Loch Ewe, Wester Ross (Mauchline, 1965 a). The largest species, M. didelphys, occurs at greater depths than the other two and, like M. gibbosa, is often common in certain areas, especially in the deep troughs of the Firth of Clyde and in some of the west coast lochs of Scotland, for example the upper part of Loch Etive.

This study forms a contribution to a series (Angel, 1969; Clarke, 1969; Baker, 1970; Badcock, 1970) describing the biological results of a detailed investigation of the ecology of an oceanic area located in the eastern North Atlantic, close to the island of Fuerteventura (Canary Islands). The scientific background and objectives of the investigation, conducted during September to December 1965, have been described elsewhere (Currie, Boden & Kampa, 1969). Our main interest lay in the biological composition and acoustic characteristics of sonic scattering layers, and it was therefore considered essential to sample the principal elements of the pelagic fauna within the depth range 0–1000 m in as quantitative and detailed a manner as was technically possible. The resulting biological collections represent a unique body of material, the analysis of which is directly pertinent to the vertical distribution, diurnal migration and ecological interrelationships of the mesopelagic fauna.

The area of Christchurch and Poole Bays has been cut by the sea in the period since the breaching of the Chalk ridge between the Isles of Wight and Purbeck late in the Flandrian transgression. Erosion of the soft Tertiary rocks must have been fast and is still active. In the Barton area the cliffs have been receding at about 1 m/year since 1895 (May, unpublished). There the cliffs are composed of badly cemented sands and sandy clays, capped with plateau gravels about 3 m thick, and erosion of them has released large quantities of sand and gravel, sufficient to maintain features such as Hurst Spit. This Spit approaches within 1.3 km of the Isle of Wight, but is separated from it by the tidal channel of the West Solent, in this area up to 60 m deep. In these narrows the south west flowing ebb current reaches 2.25 m/sec, whereas the flood current only reaches 2 m/sec.

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.

While preparing a report on Echinodermata from the Stilly Isles, based on collections made by the University of London Sub-Aqua Club but including also earlier records by various authors (F. W. E. Rowe, J. nat. Hist., in the Press), it became apparent that the species generally known as Cucumaria saxicola Brady & Robertson and C. normani Pace, from Mortensen's classic handbook (1927), have not been satisfactorily reassigned generically since the break-up of Cucumaria sensu extenso and need new generic names in conformity with current views on generic distinctions in the Dendrochirotida.

Mortensen (1927), in his survey of the Echinoderms of the British Isles, includes seven species in the genus Cucumaria: C. frondosa (Gunnerus); C. elongata Düben & Koren; C. hyndmanni Thompson; C. saxicola Brady & Robertson; C. normani Pace;C. lactea (Forbes) and C. planci (Brandt), this last species being wrongly credited to von Marenzeller.

C. frondosa is a plump to barrel-shaped animal with ten large, bushy tentacles, podia, at least in the older specimens, not restricted to the ambulacral areas, a calcareous ring with no posterior bifurcations on the radial plates or any fusion of the ventralmost radial and adjacent interradial plates and spicules of the body wall comprising thin, multilocular, smooth or slightly thorny plates, these being more or less restricted to the posterior region and to the podia in older animals. It has been designated type-species of the genus by Panning (1949), thus delimiting Cucumaria sensu stricto. The other species included by Mortensen cannot be treated as being congeneric with frondosa by virtue of their elongate body, ten relatively small tentacles of which the ventralmost two are smaller than the remaining eight, podia restricted to the ambulacral areas, calcareous ring showing a tendency, in some forms, to develop posterior bifurcations on the radial plates and fusion of the ventral-most radial and adjacent interradial plates and the differing form and combinations of spicules of the body wall.

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.

This paper represents the second and final part of a study of the depth distribution and diurnal migration of pelagic decapod crustaceans in an area of the eastern North Atlantic. Part I (Foxton, 1970) dealt with the Caridea; Part II now considers the Penaeidea. In the discussion the data as a whole are analysed and the resulting patterns of vertical distribution and migration discussed.

SOND Cruise 1965 aboard the R.R.S. ‘Discovery’ afforded the opportunity for short-term estimation of the penetration of daylight at midday into three regions of the eastern North Atlantic, evaluation of the fluctuations in the character of noonday light at depth in a restricted area over a 2-month period, and a determination of the penetration of moonlight in this area at the full of the moon.

The features of the vertical distribution of meso- and bathypelagic fishes are poorly known. Much of our present knowledge is based upon data collected on the early, major expeditions (i.e. Brauer, 1906; Murray & Hjort, 1912; Jespersen, 1915; Jespersen & Tåning, 1926; Norman, 1929, 1930; Regan & Trewavas, 1929, 1930; Benin, 1934, 1937; Ege 1934 1948, 1953, 1957; Bertelsen, 1951; Parr, 1960; Ebeling, 1962; Ebeling & Weed, 1963; Nafpaktitis, 1968). Fishing depths were not accurately determined, the depth of net generally being calculated from the length of wire out and the wire angle to the water surface. Closing nets were infrequently used. From these reports a general appreciation of vertical distributions has been possible. More recently, distribution studies mostly made in restricted areas using open nets with depths more accurately determined indicate a limited vertical distribution for each species (Aron, 1962; Pearcy, 1964; Pearcy & Laurs, 1966; Lavenberg & Ebeling, 1967; Paxton, 1967).

In recent years the general adoption of high-speed plankton samplers has given new impetus to studies of the distribution and survival rate of larval and post-larval fishes; instruments ranging in size from the small Hardy Indicator type to enlarged versions of the Gulf III have been widely employed (e.g. Glover, 1953, 1961; Gehringer, 1952, 1962; Ahlstrom, Isaacs, Thrailkill & Kidd, 1958; Bary, de Stefano, Forsyth & van den Kerkhof, 1958; Bridger, 1958; Hempel, 1959, 1964; Miller, 1961; Kinzer, 1962, 1966; Clarke, 1964; Beverton & Tungate, 1967). At Plymouth a version of the Gulf III proved exceptionally useful for rapid surveys of the distribution of macroplankton indicator species in the Western English Channel and approaches in 1958–60 (Southward, 1962).

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.

One of the puzzling features of polychaetes and some other animals is the tendency for epidermal mucus cells to become incorporated into the central nervous system (Clark, 1966). In a number of species of Nephtys an extensive prostomial mucus gland system has come into close association with the supraoesophageal ganglion of which it sometimes forms two enormous posterior lobes (Clark, 1955, 1958). Cells which are comparable to, if not homologous with, those in Nephtys are even more completely incorporated into the supraoesophageal ganglion of nereids (Bobin & Durchon, 1953; Durchon & Frezal, 1955; Hauenschild & Fischer, 1962; Herlant-Meewis & Van Damme, 1962) and glycerids (Simpson, 1959), though, unlike the situation in nephtyids, the connexion between these cells and the exterior is tenuous or even problematical in nereids and glycerids. In Pisione, superficial gland cells near the median ocelli of the trochophore larva are incorporated into the supraoesophageal ganglion at metamorphosis and form two well-defined glandular masses near the posterior eyes in the adult, losing their ducts to the exterior in the process, but retaining the appearance of gland cells (Åkesson, 1961).

Dissolved amino acids, in both the free state and combined as polypeptides, play an important part in the marine biochemistry of nitrogen. These compounds are excreted by phytoplankton (Fogg, 1962, 1966; Stewart, 1963; Hellebust, 1965) and zooplankton (Johannes & Webb, 1965; Webb & Johannes, 1965) and are utilized by algae (Syrett, 1962), bacteria (Proom & Woiwood, 1949) and marine invertebrates (Stephens & Schinske, 1961). Experiments with cultures have shown, indeed, that some species of phyto-plankton will not grow, or grow only with difficulty, if certain amino acids are absent (Harvey, 1938; Provasoli & Gold, 1957; Droop, 1957, 1959, 1962). In addition to their direct biochemical role, amino acids may also serve to complex trace metals, such as copper and iron, and keep them readily available for assimilation by marine organisms (Harvey, 1938; Fogg, 1959; Provasoli, 1963; Kent & Hooper, 1965; Saunders, 1957).

Some years ago it was shown that adult limpets, Patella vulgata (L.), could give a graded response to water of diminished salinity, the precise extent of which varied according to the tide level from which the individual was drawn (Arnold, 1957). This response, an upward movement of the front edge of the shell, accompanied by protrusion of the cephalic and mantle tentacles, was elicited by dilutions of sea water with a salinity as low as 17‰ in the case of limpets living near H.W.N.T., but was not shown to salinities below about 27‰ by those settled near L.W.S.T. Such a difference in tolerances and behaviour could be expected to play an important part in the lives of intertidal organisms, especially those of a sessile or sedentary habit, since it would permit populations inhabiting the higher levels of the shore to maintain activity despite the generally disadvantageous nature of prolonged exposure to the air. Moreover, those species capable of such adaptations might, under estuarine conditions, evolve physiologically different populations specially fitted for life under conditions of low salinity. Such studies are thus of value not only in regard to the biology of the particular species concerned, but also for fuller understanding of the general conditions of intertidal and estuarine life and their practicability as routes toward establishment of a terrestrial mode of life. Subsequent studies have revealed the salinity tolerances of a number of intertidal organisms, including those of the larvae of both the commoner barnacles and several families of polychaetes (Bhatnagar & Crisp, 1965; Lyster, 1965). Investigation with media of various compositions suggests that in both limpets and barnacles the response is essentially to the presence of chloride ion, modulated by the presence of calcium ion (Arnold, 1959; Barnes & Barnes, 1958).

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 secretion of mucus has been most intensively studied in goblet cells and mucous salivary gland cells from mammals, particularly laboratory rodents. It was therefore thought desirable to characterize mucous cells from the gut of Ciona intestinalis (L.), in which mucus has an important role in food capture, the formation of a food chain, the protection of the gut lining from physical and chemical abrasion and the formation of faeces. The alimentary canal of Ciona is composed of five regions: (I) a perforated pharynx, (II) a short tapering oesophagus, (III) an ovoid ridged stomach, (IV) an intestine and (V) a rectum. Previous authors (Roule, 1884; Yonge, 1925; Van Weel, 1940; Millar, 1953; Fouque, 1954) have described the preponderance of mucus-secreting cells which occur in the oesophagus, intestine and rectum. It is these three regions that have now been studied in more detail, with the use of histochemical and electron-microscopic techniques.