On rocky shores of the British Isles and neighbouring regions of the North Atlantic coastline, the sporophyte of Laminaria hyperborea (Gunn) Foslie is the dominant member of most sublittoral algal communities. The bathymetric distribution, like the geographical distribution, is extensive; L. hyperborea is often dominant from extreme low water level of spring tides (E.L.W.S.) to depths of up to 32 m. The great changes in environment encountered by this species over this wide range of distribution would suggest a highly adaptable organism. Changes in size, rate of growth and growth pattern have indeed been recorded between plants at different latitudes and different depths. Plants from northerly waters generally are much larger with longer stipes and have a greater frond area (Kain, 1962; Bellamy & Whittick, 1968; Greenhager, 1958), although Kain (1963, 1967) points out that this is often due to greater longevity of individuals rather than greater growth rates. Increasing depth affects the density of distribution; the typical L. hyperborea forest becomes more sparse until an open community, called 'the park' when first recorded by Kitching in 1941, replaces the forest at about 15 m. The plants in the open community are smaller than those in the forest and have shorter stipes (Kain, 1962, 1966, and observations described in this communication). However, despite these changes in growth,, almost no morphological variation had been recorded prior to the present investigation. More recently there has been a report of a form L. hyperborea f. cucullata (Svendsen & Kain) from deep water and waters not subject to water movement with thin enlarged fronds and short stipes (Svendsen & Kain, 1971; Kain, 1971).

P. platycheles was proved to be an osmoconformer, as expected. It is assumed that the other three species are conformers.

Littoral specimens of E. bernhardus have a similar salinity tolerance to P. platycheles, surviving from between 17 and 20·4‰ salinity to between 40·8 and 51‰ salinity if a median lethal time of above 500 h is taken to indicate survival.

The stenohaline species G. squamifera andP. longicornis swell rapidly and die in 60‰ s.w. (20·4‰ salinity). Their locomotion is rapidly impaired by swelling and the integument distorted.

P. platycheles, a moderately euryhaline species, is capable of resisting swelling in 60‰ s.w., and eventually regains its original weight.

Littoral E. bernhardus showed an unusual pattern of volume change in 60‰ xs.w. Initial swelling of 15·4‰ in the first hour was great compared with decapods like C. maenas or P. platycheles, yet did not cause much interference with movement, and was substantially reversed in a few hours.

Increased urine production prevents swelling in P. platycheles. It is thought that increased antennary artery pressure and or a shift to a diuretic hormone balance cause increased nitration by the antennal gland.

Increased urine production is delayed until substantial swelling has occurred in E. bernhardus.

The abdomen of E. bernhardus makes up significantly more of the total animal weight in dilute media than in full sea water, confirming the idea that the abdomen is a ‘swelling reservoir’ protecting the rest of the animal from the mechanical effects of water inflow.

Salt loss in the urine is more important than integumental loss in both E. bernhardus and P. platycheles when they are placed in 60 % s.w.

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.

Twenty-four out of 240 fishes caught by bottom lines at 366–3333 m had something in their stomachs. Stomach contents included parts of cephalopods, fish, cetaceans and bottom-living invertebrates, thin rubber sheet and terrestrial mammal bones. The material provides evidence that four species of cephalopod are at least partially demersal and suggests a means by which the tapeworm Phyllobothrium could pass from its secondary to its primary host.

During the five biological cruises of R.R.S. ‘Discovery’ between 1967 and 1971 a total of 31 bottom lines with 1483 hooks were fished in depths of water between 366 and 3333 m. The stomachs of the 240 fish caught were examined and 216 (90%) proved to be empty. The high incidence of empty stomachs is thought to be due to frequent loss of food during the ascent from great depths and accounts for our poor knowledge of the feeding habits of demersal fish living at depths exceeding 400 m.

The present collection of food from 25 stomachs (24 from ‘Discovery’ collections and one from a fish caught by Mr G. R. Forster from R. V. ‘Sarsia’) of fish belonging to 11 species (Table 1) probably gives little indication of the usual diet of the fish concerned, but its nature prompts some useful speculation and the rarity of such observations justifies placing them on record (Bigelow & Schroeder, 1948; Marshall, 1954).

All the fish were caught on lines which lay on the bottom for several hours and it is our firm belief that they were hooked while on or very near the bottom.

According to the generally adopted view, all the proprioceptors of the leg articulations of decapod Crustacea respond to stretching or relaxation of the organs caused by joint movements or joint position. This view is based on anatomical and physiological studies made, originally, mostly on crabs. It has been found, however, that in other groups of Crustacea, such as Anomura and Macrura Reptantia, some of these receptor organs are anatomically related to structures on the exoskeleton. This type of receptor organ, examined in Palinurus vulgaris Latreille, Homarus gammarus (L.) and Pagurus bernhardus (L.), is the main subject of the present paper. In the course of this work some observations have been made on other proprioceptors, particularly those in the ischiopodite-meropodite articulation, and these too are reported below. The organs in the coxal region, the special structure of which was the subject of previous investigations (Alexandrowicz & Whitear, 1957; Alexandrowicz, 1958, 1967), are not included.

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.

The luminescent material emitted from the post-cleithral organ of searsid fishes is in the form of granule-packed cells. From this material a partially purified extract may be prepared which shows some of the properties to be expected from a photoprotein. The purified material luminesces on treatment with hydrogen peroxide and, specifically, ferrous iron. The properties of the luminescent system appear similar to those of material isolated from the luminous polychaete Chaetopterus.

The jaera albifrons Leach group of species is a common component of estuarine faunas in Britain, where each species may occur in considerable numbers. Some members of the group also occur in less variable, marine localities in Britain and elsewhere, indicating that each species is capable of survival in a wide range of salinity combinations and that the group as a whole is euryhaline (see, for example, Naylor & Haahtela, 1966; Jones & Naylor, 1971). Naylor & Haahtela (1966) showed that the four species of jaera which occur in Britain occupy preferred areas on an estuarine shore such that jaera ischiosetosa Forsman is common on stones in areas affected by freshwater seepage, jaera albifrons Leach occurs on stones either in pools or in parts of the shore where water is retained (around M.t.l.), jaera praehirsuta Forsman occurs on Fucus serratus (L.), and jaera forsmani Bocquet can be found under stones around L.w.s.t.-l.w.n.t. where there is little retention of water. A later investigation by Jones & Naylor (1971) has shown that these habitat preferences persist throughout a 2-year period, and that each of the jaera species is capable of successful reproduction and development in a characteristic pattern of fluctuation in salinity, temperature and exposure to air

The reflecting layers in the external surfaces of salmon were studied during smoltification by making direct observations on the reflecting structures. The relationships between the reflecting layers in the epithelium external to the scales, in the tissues of the scales, and in the skin internal to the scales are given. Some fish, including fish blinded by pseudobranchectomy were reared under very abnormal lighting conditions and the processes of silvering and regeneration of scales followed on them. It was found that the pattern of silvering in smoltification and regeneration was not at all affected by lighting and that, although regenerated scales can easily be distinguished in other ways from those they replace, the orientations and reflectivities of their plate-lets are, with occasional exceptions, almost indistinguishable from those they replace.

Changes in blood glucose levels in teleosts have been reviewed by a number of workers. Epple (1969) considered the regulation of glucose by the insulin of the fish pancreatic islet tissue, Nakano & Tomlinson (1967) examined the regulation of glucose by the catecholamines, Black, Robertson & Parker (1961) considered glucose in carbohydrate metabolism of teleost muscle, while knowledge of regulation of blood glucose in Chondrichthyans has recently been extended and reviewed by Patent (1968, 1970). The investigation of blood glucose levels and their control mechanisms dealt with in this paper forms part of a broader study of the changes that occur when fish are caught from the wild and placed in aquaria (Wardle, 1968, 1971, and unpublished). In this study, capture is considered as a stimulus imposed on the wild fish, which initiates a series of physiological changes that can be measured as the fish adapts to the aquarium.

Adult barnacles adhere to surfaces by a secretion released on to or forced beneath the bases. This secretion has been called barnacle cement. Carderelli (1968) calculated from crude experiments that the tensile strength of Balanus eburneus exceeded 50,000 p.si., but apart from this work no other data exist on the adhesive properties of barnacle cement. More studies have been undertaken on the biochemical composition of cement (Carderelli, 1968; Saroyan et al., 1970; Cook, 1970), but the results are somewhat contradictory.

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.

Many animals have a diffuse extra-ocular sensitivity to light. Limited areas of particular dermal photosensitivity have been localized in, for example, Mya siphon (Light, 1930) and the tail of ammocoetes (Steven, 1951) but identification of the receptors is difficult. Even when candidate receptors are known, owing to their small size and the limitations of light microscopy, they have been imperfectly characterized (e.g. Light, 1930) and their identification questioned (Steven, 1963).

An account is given of the effects of changes of concentration of salts in the ambient medium on the colours reflected by the scales of herring and salmon. These lead to the conclusions (1) that in the herring in life the reflecting cells which lie under the scales and outside the scale pocket are in osmotic equilibrium with the external medium and not with the fish's body fluid (2) that the corresponding cells which lie inside the scale pocket of herring are always in equilibrium with these body fluids (3) that in the salmon all parts of the scale, including the parts outside the scale pocket, are in equilibrium with the internal body fluid and osmotically protected from the external medium.

The sense organs of the lateral-line system of lower aquatic vertebrates are mechanoreceptors which respond to water movements. They are distributed over the body, usually in lines which form a definite pattern on the head and along each side of the trunk. In the Cyclostomes the sense organs project from the body surface ('free neuromasts'); in other aquatic vertebrates they are usually housed in canals which are sunk into the dermis and which open at regular intervals to the exterior, although in some teleosts and in all modern amphibia the canal system has been secondarily lost and the neuromasts are once again situated externally.

Aspects of the physiology of the two cockles Cerastoderma edule (L.) and C. glaucum (Poiret) in air have been investigated. Both cockles exhibit bradycardia during exposure and are similarly tolerant of anoxic conditions, but C. edule survives longer in air than C. glaucum. This is accounted for by the fact that C. edule displays a behaviour pattern of valve movements upon emersion which allows air-breathing. Oxygen uptake rates of this cockle measured in air lie close to the lowest rates recorded in water, and are considered to approximate to a basal or quiescent level. C. glaucum does not air-breathe and is restricted to lowest shore levels. Values for ‘maximal’ levels of oxygen uptake in water have also been obtained together with estimates of metabolic scope for the cockle.

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.

Few observations on living pterobranch hemichordates have been published. Gilchrist (1915) and Andersson (1907) have observed living zooids of Cephalodiscus; while Sars (1874), Schepotieff (1907) and Burdon-Jones (1954, 1957) have observed living Rhabdopleura. No observations appear to have been published on living Atubaria. Recently R. compacta Hincks was discovered near the Plymouth Laboratory (Stebbing, 1968) and during our work (Dilly, 1971, 1972a, b; Stebbing, 1970a, b) we have made some observations on living specimens. Attempts to keep R. compacta alive for long periods have not been completely successful (Stebbing, 1970), although Burdon-Jones (1954) managed to study the salinity tolerances of/?, normani Allman for more than 2 months in the laboratory. He has also studied feeding behaviour in living zooids (Burdon-Jones, 1957) Our observations have been made on specimens maintained in recirculation systems over periods of up to 12 weeks.

Pressure waves moving across the sand beds at 3 m depth at Le Racou caused circulation of water in the unconsolidated sand layer. The pattern of circulation apparently depended on the depth of the unconsolidated layer and the form of the sand ripples. The rate of flow was determined by the height of the surface waves and the permeability of the deposit. The physical properties of the sands at the crests and in the troughs of the ripples were in part determined by the organic component which in turn would have been governed largely by the patterns and flow rates of the interstitial currents supplying organic material and nutrients to the sand. Differences in the physical properties of the sediment at the crest and in the trough of a ripple due to the organic component were such as would have affected substantially the prevalence of Branchiostoma lanceolatum and harpacticoid copepods. Sand properties dependent on the organic component would clearly be subject to change in accordance with the prevailing weather conditions and hence the supply of organic material. The role of irrigated sands in the removal of organic material from shallow seas is discussed.