This investigation of the ultrastructure of the cells of laminarian haptera is part of a more detailed study of the growth of marine macroalgae and their inter-action with the environment. A major section of the programme is an attempt to establish the relationships between physiological, biochemical and structural (including ultrastructural) changes which occur during cell growth in brown algae and to compare such observations with those recorded for higher plant cells.

The choice of haptera (PI. IA) for much of this work on brown algal cell growth is based on their suitability for the interpretation of enzymological data on a cellular basis. Hapteron growth shows several convenient similarities to that in primary meristems of higher plants. Although lamina growth is from an intercalary meristem at the base of the lamina (transition zone), hapteron growth is essentially apical (Reinke, 1876), and differentiating cells are arranged in rows leading backwards from the apex (PI. IB, c). Thus, progressive sections cut from the tip backwards will contain an increasing percentage of vacuolate, elongating cells, as in the flowering plant root.

Competition for space between sessile animals on the seashore and sublittorally is an important factor in their ecology. This is partly because of their density, but also because competition for space between sessile animals is of a more severe kind than occurs between free-living ones, for they cannot move away from their competitors.

Occasional reference to the sporadic appearances of silicoflagellates (commonly Dictyocha spp.) are to be found in a number of seasonal studies of phytoplankton in the coastal waters of the British Isles. The silicoflagellates are rarely described in any detail since they usually form a small component of the annual phytoplankton. The autumnal occurrence of silicoflagellates in the Firth of Clyde was briefly described by Marshall (1924) in an account of the food of Calanus, and further seasonal observations on silicoflagellates in European coastal waters are to be found in the works of Margalef (1965), Nival (1965), Travers & Travers (1968) and Ignatiades (1970). Numerous studies on silicoflagellates have been concerned with their taxonomy, particularly the plasticity of form shown by their tubular siliceous skeletal structures and the many taxa (fossil and living) so far described. The confusion which has arisen through the differing views of palaeontologists studying fossil material, and botanists working with live populations and their seasonal abundances, has been highlighted recently in a culture study of Dictyocha fibula, in which skeletal variations in a single clone were matched with a number of other entities, fossil and living (Van Valkenburg & Norris, 1970).

In a previous paper Bayne & Thompson (1970) showed that temperature and nutritive stress resulted in a decline in body condition of mussels, Mytilus edulis, when kept in the laboratory. Both carbohydrate and protein were lost from the body tissues but the losses (as a percentage of the initial values) were greater from the germinal (mantle) than from the somatic (non-mantle) tissues. In spite of the loss of body reserves, M. edulis was able to continue maturation of the gonad during the autumn to spring period. In the early summer, however, when the gametes were fully ripe, stress resulted in a recession of the gonad and a rapid loss of protein from the mantle tissues. A similar decline in condition index and loss of glycogen and protein has been reported for adult oysters, Ostrea edulis, when maintained under hatchery conditions (Gabbott & Walker, 1971).

Although a great deal is known about methods for the culture of commercially important bivalve larvae (see, for example, Loosanoff & Davis, 1963; Walne, 1964, 1966) little information is available on the biochemical changes that take place during larval development.

Collyer (1957) determined the glycogen content of several batches of newly released larvae of Ostrea edulis and found that viability was not related to the initial glycogen content. Millar & Scott (1967) showed that lipid was the major energy reserve used during starvation by newly released O. edulis larvae. Recently Helm, Holland & Stevenson (1973) have shown that the initial growth rate of newly released O. edulis can be positively correlated with the lipid content of the larvae on liberation.

The present paper describes the biochemical changes that occur during larval development, metamorphosis and early spat growth of O. edulis. In addition, short-term starvation experiments were carried out to determine whether protein, lipid or carbohydrate serves as the main energy reserve during each phase of development.

The nature and the quantity of run-off into coastal waters will to a large extent influence the occurrence and distribution of a number of chemical components such as nutrient salts, organic matter and trace metals in these waters. In open coastal environments the run-off is usually quickly dispersed and diluted so that little of it remains at concentrated levels in the vicinity of the discharge point. On the other hand, if such discharge is made into closed or confined waters, the rate of dispersal will depend on the circulation pattern and the rate of flushing of the run-off. Thus in some areas where the circulation is restricted, a build up of compounds may occur which, depending on the run-off composition, may have a marked effect on the ecology of these waters. The situation may be further aggravated if the run-off includes large quantities of industrial and domestic waste.

Glycollic acid is probably a major component of the extracellular organic fraction liberated during phytoplankton photosynthesis and presumably plays an important part in energy transfers in aquatic environments (Fogg, 1966). It has been difficult to investigate these possibilities, however, because of the lack of a reliable and convenient method for the determination of glycollate in natural waters. With fresh water, ionexchange resins have been used for separating and concentrating glycollate which may then be estimated colorimetrically using Calkins's method (Fogg, Eagle & Kinson, 1969). This method is time consuming and is much more difficult and laborious with sea water because of the presence of high concentrations of inorganic ions. Koyama & Thompson (1964) determined various organic acids after extraction from sea water with organic solvents but this method is also laborious and for glycollic acid yields ambiguous results. Andrews & Williams (1971) measured free amino acids and also glucose occurring in sea water in μtgl−1 concentrations by retaining them on a copper chelating resin and a charcoal column respectively and eluting them with ammonium hydroxide or 10% ethanol as appropriate.

This paper is concerned with the biology of the sandeel, Ammodytes tobianus L., in Langstone Harbour, Hampshire; this was the main area studied in a survey of sandeel populations which are exploited for bait along the south coast of England. Aspects considered are the relative occurrence of the spawning groups; spawning seasons; population structure in terms of length, sex, age and maturity; mortality; annual growth; seasonal growth; and condition. The seasonal pattern of otolith growth and its application to the back-calculation technique, has been described elsewhere (Reay, 1972).

A. tobianus forms over 95% of the total sandeel catch in Langstone Harbour. Hyperoplus lanceolatus (Le Sauvage) is the only other species to occur regularly, but individuals of the three other British species, A. marinus Raitt, H. immaculatus (Corbin), and Gymnammodytes semisquamatus (Jourdain), have also been recorded. This pattern of species composition is also found in the other inshore areas studied along the south coast.

Records of the occurrence of postlarval stages of teleostean fishes in the plankton off Plymouth have been kept for a period of nearly 50 years. During that period noteworthy changes in the abundance of postlarvae have taken place. While in the 1920s postlarvae were very abundant in the plankton, in the 1930s they became much fewer at about the time when the herring fishery declined. Somewhere around 1965 another change took place and post-larvae became once more very abundant. There was also a marked increase in the quantity of macroplankton, which like the young fish had become much reduced in quantity in the 1930s (Russell et al. 1971).

The blue shark is a pelagic species having a virtually circumglobal distribution in tropical and temperate seas. In the northern hemisphere, during the warmer months, they extend their range northwards in both the Pacific and Atlantic (Strasburg, 1959; Bigelow & Schroeder, 1948; Templeman, 1963). Between May and October they occur regularly and in considerable numbers around the south-west peninsula of England. Strasburg showed that in the central Pacific blue sharks are opportunistic feeders as were the other pelagic species he studied, their diet consisting mainly of squid and small fish. Bigelow & Schroeder suppose herring (Clupea harengus L.), mackerel ((Scomber scombrus L.), sardines (Sardina pilchardus Walbaum) and a variety of cephalopods to be the chief diet in northern waters, together with Squalus acanthias L. and various bottom fish on the fishing banks. In warmer waters anchovies (Engraulis encrasicolus L.), flying fish and the occasional sea bird caught resting on the water are known to occur in their diet. Bigelow & Schroeder also quote the well-known stories of blue shark following boats for offal and feeding on the carcasses of harpooned whales. Le Brasseur (1964) examined the diet of blue sharks caught by gill net in the Gulf of Alaska and in general confirmed Strasburg's observations. However, he stated that when salmon (Oncorhynchus sp.) were available in gill nets blue shark might selectively feed on them, while by-passing other readily available species occurring in their normal diet. Couch (1862) examined the stomachs of two specimens from Cornish waters, finding herring, mackerel and garfish (Belone belone L.), as well as Squalus and Conger conger L. Lo Bianco (1909) found anchovies and cephalopods in one of two specimens caught in the Bay of Naples, the other of which contained large numbers of flying-fish eggs (Exocoetus sp.).

During an examination of the distribution and relationships of muscle receptor organs in the hermit crab, Pagurus bernhardus (Pilgrim, in preparation), it was found that not enough was known about the muscular anatomy of the animal for the experimental work to be described satisfactorily. This paper is therefore an account of the anatomy appropriate to a better understanding of the receptor organs. In the preparation of this account, it was necessary to examine the skeleton of the animal in great detail, since a knowledge of the relationships of especially the movable skeletal parts is basic for an understanding of the muscular system. The study also forms part of a series in which the comparative anatomy of the axial skeleto-muscular systems is examined in the Decapoda. This paper falls naturally into two parts, dealing respectively with the skeleton and the muscles. Although emphasis in this work is on the trunk anatomy of the last six segments of the thorax, it is necessary to extend observations beyond this region for certain interpretations.

Studies of the distribution of china clay waste and its effects on the bottom communities off the south coast of Cornwall, initiated by Portmann (1970) and Howell & Shelton (1970), have been supplemented by further surveys, the results of which will appear in future papers by Shelton & Rolfe (in preparation) and Probert (in preparation). This paper describes two polychaete species which have been discovered in this area, namely the hesionid Gyptis capensis (Day) and the ampharetid Sosane sulcata Malmgren. From the zoogeographical viewpoint, the records of both species are of great interest: hitherto, G. capensis was known only from southern Africa and the tropical West Pacific region, and S. sulcata from Scandinavia, West Scotland and the Mediterranean.

Pogonophora are long thin tube-dwelling invertebrates similar in size to polychaetous annelids, but lacking both mouth and gut, and found mainly in the deep sea. Current discussion of their systematic position had revealed a need for more information about particular aspects of their morphology and embryology (Southward, 1971a). The earlier attribution of Pogonophora to the echinoderm-chordate group, Deuterostomia, based mainly on their apparently tricoelomate structure, has been questioned recently, following the discovery of the previously unknown posterior end (Webb, 1964a; Ivanov, 1965). This posterior end is a small and delicate structure composed of several coelomate segments separated by septa and provided with short bristles. It has such a strong resemblance to the posterior end of an annelid, though of course it does not contain a gut, that there has been much speculation about the possibility of a relationship between Pogonophora and Annelida and some reconsideration of the features thought to indicate affinity to the Deuterostomia (Livanov & Pornrieva, 1967; Webb, 1969b; Ivanov, 1970; Norrevang, 1970a, b; Southward, 1971a).

The tunicate heart has been extensively studied, with particular recent emphasis on the physiology of heart reversal (see Krijgsman (1956) and Kriebel (1968) for reviews). The salp heart, however, has received much less attention (Schultze, 1901; Nicolai, 1908), mainly because of the difficulty of maintaining this delicate marine animal in the laboratory. Thus the structure and function of the salp heart has been assumed to be similar to that of the sessile tunicates (Ihle, 1935; Berrill, 1950).

It is usually very difficult to obtain knowledge of predator-prey relationships in the marine plankton. However, because of the very specialized nature of this relationship, where the copepod spends part of its life as a parasite and part of its life as a predator, detailed understanding of the relationship has been obtained from both laboratory and field observations.

The usual concept of predation involves a predator which is the same size or larger than its prey. This prompted Foxton (1966), in discussion of the large salp Salpa thompsoni, to consider only the gut contents offish, sea birds, seals, etc., when analysing data on predation. He noted that considerable mortality occurred between the embryos and the adult stages which did not appear to be explained by the data on predators which he considered. He concluded that ‘further study is necessary before (the salp's) true role can be defined’.

Copepods and amphipods are often associated with salps in distribution (Hardy, 1936), usually being regarded as parasites (Furuhashi, 1966; Wolfenden, 1911). Amphipods which lay their eggs directly into the living tissue of salps have been described (Haruhiko, 1967), while the use of the salp test as a protective house by the amphipod Phronema is well known (Hardy, 1956).

Dense swarms of Thalia democratica occurring in S.E. Australian waters are often associated with high densities of Sapphirina copepods (Dakin & Colefax, 1940; Thompson, 1948; Sheard, 1965). Observations of these swarms underwater, by the author, show the presence of many Sapphirina copepods inside salps in the undisturbed state, as in Plate I (A).

Among the marine invertebrates whose settlement behaviour is well studied, the polychaete tubeworm, Spirorbis spirorbis L. ( = borealis Daudin), the barnacle, Balanus balanoides, and the oyster, Ostrea edulis, are different in form whether in the free-swimming or adult stage, yet the settlement behaviour patterns are basically similar (Crisp, 1973). The larvae have a sequence of movements during exploration of the substratum, with each activity initiated by a hierarchy of stimuli. Given a positive set of responses to a suitable habitat, the distances moved on the substratum are limited progressively so that finally the larva investigates a very restrictred area. When the exact site for settlement is determined the larva ceases to move, attaches permanently and immediately commences metamorphosis into the adult form. However, if certain stimuli are lacking or obnoxious to the searching larva, it recommences the initial free-swimming activity, in order to reach alternative substrata.

Frontal horns are prominent structures, characteristic of the nauplii of most cirripedes. Such horns are more prominent amongst the Lepadomorpha, i.e. Lepas (see Groom, 1894).

Reference is made to frontal horns in those papers concerned with the identification of nauplii (Nilsson-Cantell, 1921; Herz, 1933; Bassindale, 1936; Batham, 1946; Pyefinch, 1948; Buchholz, 1951; Barnes and Barnes, 1959a, b), but more detailed descriptions of horns and associated gland cells are limited to the studies of Groom (1894), Kaufmann (1965) and Walley (1969).

In the present study, the morphology of the frontal horns and the cytology of associated frontal horn gland cells of three barnacle species - Balanus hameri (Ascanius), Balanus balanoides (L.) and Elminius modestus Darwin were investigated.