Knowledge of the distribution of molybdenum in sea water is needed for an understanding of the behaviour of the element in the geochemical cycle of weathering and sedimentation and for the assessment, in relation to environmental levels, of its possible utilization by marine organisms. The principal measurements of molybdenum in sea water are summarized in Table 1; the results of earlier investigations (Ernst & Hoermann, 1936; Bardet, Tchakirian & Lagrange, 1938; Noddack & Noddack, 1940) are excluded from this summary as later work suggests that they were inaccurate. The summary indicates that molybdenum is a comparatively uniformly distributed trace element in sea water with a concentration usually in the range of 9–13 µg/l. Except for waters directly affected by continental drainage or other localized influences, the only values appreciably below this range appear to be those reported by the early workers cited above, by Zhavoronkina (1960) for a single sample from the Atlantic, and by Brooks (1965) for waters off New Zealand.

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.

Several authors have studied the rhythmic behaviour of amphipods, including Papi (1955) who demonstrated an endogenous solar time sense in Talitrus saltator which was used for navigation. Talitrids were also investigated by Featherston & Maclntyre (1957) who suggested that changes in light intensity triggered the nocturnal foraging activity. Enright (1961, 1962, 1963) tested the effects of pressure, temperature, light intensity, absence of sand and shaking on rhythmic behaviour of the intertidal and in-faunal amphipod Synchelidium. The activity rhythm of Corophium volutator has been reported by Morgan (1965) in which a peak occurred on the early ebb. Various rocky shore Peracarida including species of Gammarus also perform vertical migrations into the surf at night (Jansson & Källander, 1968); the inhibiting effect of light was proven by experiments with controlled illumination.

Many metallic elements are concentrated by marine animals to levels far in excess of their concentrations in sea water itself. This concentration extends not only to those elements which are known to have biochemical functions, but also to others which have no established biological role (e.g. cadmium and lead). Little is known about the mechanisms by which trace elements are concentrated, or about the manner in which they are held in the tissues. As a preliminary to the investigation of concentration mechanisms, reliable data are required concerning the distribution of the elements in a variety of marine animals.

Recently Lochhead (1968) has described the feeding and swimming behaviour of Conchoecia based on observations of C. spinirostris Claus and a species that was probably C. curta Lubbock. During the last four biological cruises by R.R.S. ‘Discovery’ observations have been made on living specimens of C. spinirostris which supplement Lochhead's observations.

When littoral animals are exposed by the receding tide they are subjected to the environmental factors of what is essentially a terrestrial environment. Of these factors desiccation (see Davies, 1969) and temperature are of paramount importance. In winter the animals may be subject to a rapid change from the relatively high temperature of the sea to a very much lower air temperature. In summertime the opposite is true and the animals will spend the dry phase in air temperatures often far in excess of sea-water temperatures. The most important temperatures from an ecological point of view, however, are the body temperatures of the animals themselves. As shown by Southward (1958) this cannot be deduced from measurements of air temperatures, since the animals are subject to heating by absorption of solar radiant energy and this in turn may be mitigated by other environmental factors.

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.

A pure-cone retina has been reported in the larval stages of teleosts from three families, viz. the salmon Oncorhynchus spp. by Ali (1959), the herring Clupea harengus by Blaxter & Jones (1967) and plaice Pleuronectes platessa by Blaxter (1968 a). There is also an absence of any retinomotor responses (movement of retinal masking pigment and changes in the relative positions of the visual cells) until the rods develop, which is usually at metamorphosis where this is clear-cut. Most adult teleosts are known to have a duplex retina.

There is now much information from field observations and laboratory experiments on pollution by oil and oil-spill removers (‘detergents’) in inshore waters and littoral habitats in SW England following the wreck of the Torrey Canyon on the Seven Stones Reef. Field observations with particular reference to plant life were reported by O' Sullivan & Richardson (1967), Spooner (1967), Nelson-Smith (1967), and Bellamy et al. (1967). A detailed survey of the biological effects of the disaster has been published (Smith, 1968). Further data dealing with littoral and sublittoral algae have been reported by Ranwell (1968), Bellamy & Whittick (1968), Boney (1968) and Nelson-Smith (1968). It has been shown from both field observations and laboratory experiments that the larger fucoid algae were more tolerant of both the oil and the oil-spill removers than the smaller algae in the region of high-water mark.

Marinogammarus obtusatus Dahl, an intertidal amphipod, was first described by Dahl (1938). Prior to this date it appears that this species was often confused with and identified as M. marinus. In later years, M. obtusatus has been shown to be common around the coast of Britain (Sexton & Spooner, 1940), and in a preliminary survey of Cullercoats Bay, Northumberland, we have found that this species is by far the commonest amphipod present.

The stomach is the principal region of extracellular digestion in the alimentary tract of Ciona intestinalis (L.) (Yonge, 1925; Morton, 1960). The region is oval and has a lining epithelium thrown into 30 or 40 longitudinal ridges. Previous authors have described the following cell types in this gastric epithelium: a mucous cell (Roule, 1884; van Weel, 1940); an un-differentiated cell (Yonge, 1925; Millar, 1953; Fouque, 1954); an absorptive cell (Yonge, 1925; Berrill, 1929; van Weel, 1940; Morton, 1960); a storage cell (Yonge, 1925; van Weel, 1940) and several different secretory cells (Roule, 1884; Yonge, 1925; Berrill, 1929; van Weel, 1940; Millar, 1953; Fouque, 1954; Morton, 1960). The present paper reports a re-investigation of the gastric epithelium by histochemical methods and by electron microscopy, and a comparison of the observations with those of previous authors. The fine structure of the gastric cells is compared with that of cell types in the ‘liver’ of Pyuridae (Degail & Lévi, 1964) and in the alimentary tract of other animals.

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 genus Bathyporeia has featured in many reports on the ecology of sandy beaches, yet little is known of the annual reproductive cycles of the species in British waters. Watkin (1938,1939a, b, 1941, 1942) has studied the taxonomy and aspects of the ecology of the genus, and more recently Salvat (1967) has described the annual reproductive cycle of B. pilosa Lindstrom, B. pelagica (Bate), B. sarsi Watkin and B. guilliamsonia (Bate) on the west coast of France. The present report is the result of an investigation into the vertical distribution and annual reproductive patterns of B. pilosa and B. pelagica on a sandy beach at Ynyslas, Cardiganshire. Whilst enabling comparisons to be made with Salvat's data, this study also forms the basis for an investigation into the ecophysiological complex of B. pilosa and B. pelagica.

It has been suggested (McLusky, 1968 a) that migrations of Corophium volutator (Pallas) may occur in response to salinity. This suggestion was based on distributional evidence from the estuary of the River Ythan, Aberdeenshire, and assumed that the animals are able to detect salinity and exhibit a behavioural response to it. The presence and nature of such a response has been investigated by means of choice experiments. Burrowing, swimming and feeding behaviour of C. volutator have been studied by Meadows & Reid (1966) and Morgan (1965).

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.

The common dog-whelk, Nucella (= Thais, = Purpura) lapillus (L.), is often selected for ecological, physiological and genetical study. In recent years most workers have based their investigations on the work of Moore (1936; 1938a, b) and most have used his observation that ‘at the onset of maturity, growth of the (shell) lip ceases and instead the region near the lip thickens, while the lip itself becomes rounded and a series of rounded “teeth” develop on its inner side which still further occlude the opening’. It has been assumed that all animals showing these features are adult, and have ceased growing, for Moore goes on to say ‘occasional specimens are taken in which the presence of a second set of teeth within the marginal ones indicates that the original stoppage of growth was followed by a second slight growing period, this in turn being replaced by a second period of thickening and growth stoppage, but such specimens are too rare to be a serious source of error.’ This assumption has been incorporated into most subsequent reviews of shore ecology.

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.

Eurydice pulchra Leach is a common intertidal isopod of sandy beaches. Its occurrence around the British Isles has been described by Jones & Naylor (1967), and Salvat (1966) has described the life cycle and intertidal distribution of the species on the west coast of France. There are several records of its intertidal distribution in Britain (Elmhirst, 1931; Pirrie, Bruce & Moore, 1932; Rees, 1939; Watkin, 1942; Brady, 1942; Holme, 1949; Southward, 1953; Colman & Segrove, 1955; Perkins, 1956; M. Ladle, unpublished) and these suggest that its distribution is variable. Watkin (1942) found that the population structure of E. pulchra in late March and early April was comprised of ‘two distinct groups’ and similar findings were made in July by Scott (1960). The present study was made on a large intertidal population in the sands of the Dovey Estuary, Cardinganshire.

Suspended organic matter in the oceans has been studied by many authors. In a review of the subject Parsons (1963) states that the occurrence of detritus particles in the oceans seems to be a universal characteristic of sea water. The greatest concentrations of suspended organic matter are to be found in turbulent inshore water masses.

When first described, as the type species of a new genus (Butcher, 1952), Pavlova gyrans was thought to be separable from Ochromonas by only one major character, namely the lateral instead of the supposedly terminal insertion of the strongly anisokont flagella. It was therefore natural to include it in the class Chrysophyceae and to interpret other structural features in accordance with this view. This practice has been continued to some extent subsequently and the three named species which are now recorded in the literature are all in varying degrees in need of emended descriptions. For this particular genus is deceptive. Not only are there unusual fixation difficulties, as already noted by Butcher, but even when examined alive its appearance can suggest the presence of characters which are not in fact what they seem to be and mask others which are essential for taxonomic guidance. Even when all these difficulties have been overcome, certain details are so unusual as to be without known parallel among the ‘brown’ flagellates which have so far been studied with the electron microscope.