The life history and taxonomic position of Rhodymenia palmata (Linnaeus) Greville, one of the commonest red algae in the northern hemisphere, have been a source of considerable speculation. Carpogonial plants and carposporangial plants are unknown although tetrasporangial plants are common and spermatangial plants have been reported on numerous occasions. A parallel situation occurs in the genus Halosaccion Kützing for which carpogonial and carposporangial plants have never been recorded and spermatangial plants are well known only in the species Halosaccion ramentaceum (Linnaeus) J. G. Agardh. It is proposed in this paper to consider the relationship of Rhodymenia palmata to the other genera of the Rhodymeniaceae (Rhodymeniales) particularly Halosaccion and Leptosarca Gepp & Gepp.

Heteromorphic life histories are now known for a number of species of Bryopsis, B. halymeniae Berth. (Hustede, 1964), B. monoica Funk (Rietema, 1971a), B. plumosa (Huds.) C.Ag. (Rietema, 1969, 1970) and B. hypnoides Lamour. (Rietema, 1971; Bartlett & South, 1973). Further it has been shown by Rietema (1970, 19716) that for both B. plumosa and B. hypnoides the life history changes with latitude.

Within the Chromophyta (sensu Christensen, 1962) a number of genera having benthic phases in which the vegetative cells are embedded in masses of thick, sometimes stratified mucilage, have been described from both marine and freshwater habitats. Examples include Gloeochrysis Pasch. (Pascher, 1925), Geochrysis Pasch. (Pascher, 1931), Sarcinochrysis Geitl. (Geitler, 1930), Chrysotila Anand (Anand, 1937) and Ruttnera Geitl. (Geitler, 1942). In many cases the vegetative stages are so similar morphologically as to be almost indistinguishable, especially in the juvenile condition in which the cells are often arranged in regular blocks (the ‘Sarcinochrysis’ condition) and under such circumstances it is difficult to ascertain their true systematic relationships.

In 1930, Colman (1933) made a study of the zonation of common intertidal animals and plants on Blackstone or Church Reef, Wembury. Four lines were marked out across the reef, and three of these, which radiated from his so-called ‘Central Rock’, were resurveyed during the summer and autumn of 1973. Besides the authors, help was given in the 1973 survey by Mr P. G. Corbin, Dr P. E. Gibbs, Dr P. K. Probert, Dr A. J. Southward, Mr R. L. Barrett and Mr T. J. Perry. Mr G. A. W. Battin was responsible for surveying and levelling, and Mr D. Nicholson for the photography.

The use of diversity and evenness indices is well established in recent ecological literature. Many indices have been proposed, to such an extent that the choice of a suitable index became somewhat of a problem. Recently, however, Hill (1973) introduced a unifying notation where diversity numbers are denned in relation to Rényi's definition of a generalized entropy. Hill showed that his diversity numbers Na of the oth, 1st and 2nd order coincide with three important diversity measures which have been frequently used, No = S, N1 = eH and N2 = 1/SI, where S is the number of species, H is the shannon-Wiener information function –Σpi In pi and SI is Simpson's index . According to this notation, evenness should be calculated by dividing two of Hill's diversity numbers, e.g. N2/N1 = eH/S. This index was proposed by Sheldon (1969), but its use in ecological literature has been negligible. The most commonly used evenness index has been the one proposed by Pielou (1966), e = H/Hmax, with Hmax = lnS. Contrary to Hill's (1973) statement, it shares with Hill's continuum of evenness measures the property of remaining constant when the number of individuals of all species is multiplied with a constant factor. Intuitively, this seems to be a necessary property of an evenness index.

The current interest in diversity as one of the major parameters describing a community has led to an increasing number of published results and theoretical discussions during the last years. Diversity has variously been related to other attributes of the community or properties of the environment, among which time, spatial heterogeneity, stability, primary production, productivity, competition, predation, niche structure and evolution. Although this rather overwhelming amount of possible relations seems somehow too much of a good thing, the importance of diversity remains well established in current ecological theory. One of the most important applications of diversity indices is their usage in the biological assessment of pollution. This immediately raises the problem of comparing diversity indices within habitats in time or between habitats in communi-ties. These comparisons are frequently made, yet the statistical significance of the observed differences or similarities is seldom mentioned. A test for these differences was formulated by Hutcheson (1970) but it apparently failed to attract the attention it deserves. In this study it was our purpose to investigate the distributions of the more important diversity indices and their evenness components in a low-diversity community of meiobenthic copepods of a shallow brackish water pond in northern Belgium. In this habitat the number of species is rather low, which greatly simplifies the analysis, and we hope that the statistical behaviour of the indices we find will hold for other, especially other low diversity communities as in polluted environments, as well. We chose copepods because they are taxonomically well known, the benthos because it is approximately two-dimensional and a shallow environment because of the possibility of accurate sampling.

A number of procedures are now available for calculating the effects of ionic inter-actions on the behaviour of solutions as complex as sea water (Whitfield, 1973 a). These procedures are able to give a good account of the properties of the major electrolyte components (Leyendekkers, 1973 a; Robinson & Wood, 1972; Whitfield, 19736) and of the colligative properties of sea water (Robinson & Wood, 1972; Whitfield, 1973 c, d). However, greatest interest centres around the possibility of predicting the effects of these major components on the multitude of ionic equilibria that influence the properties of the less abundant constituents that are of greater biological and geological importance. It is here that the newer approaches to marine chemistry are weakest because suitable thermodynamic data are lacking. One system of practical importance that can be studied using a variety of theoretical approaches is the acid ionization of ammonium ions represented by the equation The toxicity of ammonium salts to freshwater life has been shown to be strongly dependent on the pH in a manner that is consistent with un-ionized ammonia (NH3) being the most lethal fraction (see, for example, Wuhrmann & Woker, 1948; Downing & Merkens, 1955; Lloyd & Herbert, i960; Hemens, 1966; and Brown, 1968). These papers and many others have been thoroughly reviewed (EIFAC Technical Paper no. 11, 1970, Kemp, Abrams & Overbeck, 1971). The free base (NH3) has a relatively high lipid solubility because it carries no charge and is therefore able to diffuse quite readily across cell membranes (Fromm & Gillette, 1968).

A study of the dissolved inorganic salts of nitrogen, silicon, phosphorus and carbon and their particulate forms in the Bristol Channel (Abdullah, Dunlop & Gardner, 1973) has shown that the primary sources of these elements are run-off and waste disposal. Furthermore, the slow flushing rate of the Channel plays an important role in the accumulation of these materials in the eastern part. An important constituent of run-off is the heavy metal load especially in industrial waste. Some preliminary investigations (Abdullah, Royle & Morris, 1972; Butterworth, Lester & Nickless, 1972; Nickless, Atenner & Terille, 1972; Preston, 1973) have shown that certain trace metals such as Cu, Pb, Cd, and Zn are added to the Channel in sufficiently large quantities to produce high concentrations not only in the waters of the Severn Estuary and Swansea Bay, but also in the local fauna.

Regeneration of ectoderm and mesogloea, and the interactions of these layers, in the sea anemone Calliactis parasitica (Couch) have been studied by examining the healing of simple wounds. Studies included the part played by the mesogloeal cells, the origin and functions of which have been much debated.

A second species of angler-fish, Lophius budegassa Spinola, 1807, is reported from British waters. This species has hitherto been reported only as far north as the Bay of Biscay. This is not thought to be an active extension of the range of this fish but to be due rather to failure to identify it, for specimens (misidentified as L. piscatorius) dating from the last century have been found in the British Museum (Natural History) collection.

The distinctive characters of both species are given.

For a long time, eggs of the garpike Belone belone have been the subject of intensive and thorough studies on the early embryology of teleosts (Ryder, 1882; Sobotta, 1896; Ziegenhagen, 1896; Kopsch, 1901; Borcea, 1909). This can be attributed to the fact that the eggs of Belone are fairly large in size (3.0 to 3.5 mm diameter, Ehrenbaum, 1905), and easy to collect from submerged plants. Ryder (1882) already used artificially fertilized eggs of Belone for his study on the circulatory system of teleosts.

Euryhaline fishes, such as the salmon and the eel, adapt the osmoregulatory mechanisms of their gills, kidney and intestine so that they retain water while they are in the sea but retain salt while in fresh water (e.g. Krogh, 1939). Thus on entering fresh water the osmotic pressure of plasma in the Atlantic salmon, Salmo salar L., only falls from some 410 m-osmole/1 to about 340 m-osmole/1 (calculated from the freezing point data of Benditt, Morrison & Irving, 1941), although the osmotic pressure of the environment falls from around 1000 m-osmole/1 to almost zero.

The inshore fishery for the pilchard in Cornish waters has existed for several hundred years, and such records as are available concerning fluctuation in catches and market conditions have been reviewed by Couch (1865), Cushing (1957) and Culley (1971). Although pilchard have been landed from Lyme Bay, from the eastern half of the Channel, and from the southern North Sea (Couch, 1865; Furnestin, 1945; Cushing, 1957; personal communications G. T. Boalch) the catches have usually been incidental to other fisheries and more sporadic than in Cornish waters. Traditionally there are three areas fished for the Cornish pilchard: on the north-west coast around St Ives; in Mounts Bay and towards the Scillies; and between the Lizard Pt and Bolt Tail in Devon (Couch, 1865; Culley, 1971). The latter region, constituting the inshore waters of south-east Cornwall and south Devon, effectively forms the eastern limits of the regular occurrence of commercial shoals. Knowledge of the breeding and life-history of the fish in this region has always been scarce and subject to much hearsay evidence (reviewed in Southward, 1963). Up to quite recently it was thought that the main spawning area lay well to the west of the entrance to the Channel, and it was not until the investigations reported by Corbin (1947,195°) a nd Cushing (1957)tnat it was conclusively shown that extensive spawning can occur within the English Channel from May to October. The relationship of the spawning in the western Channel to the other areas of spawning off the entrance to the Channel and in the northern Bay of Biscay is illustrated in a recent series of reports (Arbault & Boutin, 1968; Arbault & Lacroix-Boutin, 1969; Arbault & Lacroix, 1971; Wallace, P. D. & Pleasants, C. A., duplicated ICES meeting paper CM 1972/J: 8), and is further demonstrated by Demir & Southward (1974) in discussing the results of a study of small scale seasonal changes in spawning intensity in inshore waters.

The marine Amoebida have not been investigated nearly as extensively as freshwater and soil species of that order. In North America, where they have received the most attention, they have been studied most by Schaeffer (1926), with more recent work by Bovee (e.g. 1956), Sawyer (1968, 1971a, 1911b, 1974a, 1974b, papers in preparation), and Page (1970, 1971a, 1971b, 1972a). Grell (1961, 1966) and Grell and Benwitz (1970, 1971a, 1971b) have investigated some interesting amoebae from European and African marine habitats. Droop (1962) described a new species of amoebo-flagellate (Amoebida, Vahlkampfiidae) from brackish water in Scotland, but otherwise there is little literature on British marine Amoebida. Some recent work on the British fauna was reported by Page (1972b, 1973, 1974).

The spatial settlement of marine invertebrate larvae is not a random process. The distribution of the adults of a particular species is influenced by the behavioural responses of the animal to a range of environmental stimuli which, in the case of many sessile invertebrates, result in the display of clear substrate selection. The role of habitat selection in determining the distribution of aquatic invertebrates has been the subject of a review by Meadows & Campbell (1972). The selection of algal substrata by the larvae of various intertidal species of Bryozoa has been demonstrated by Ryland (1959); among these, the ctenostomatous bryozoans Alcyonidium hirsutum and A. polyoum were shown to exhibit a strong preference for fronds of the alga Fucus serratus, an experi-mental result which accorded well with the distribution of the two species on the shore (Ryland, 1962).

As the processes by which epiphytic bryozoans become established in aggregations on intertidal algae become more clearly understood, it is necessary to consider some of the ecological consequences of non-random settlement. The adaptive significance of aggregation in epiphytic bryozoans has been discussed recently by Hayward & Ryland (1974), who also showed how the worst effects of overcrowding are mitigated. Acorn barnacles and spirorbine tubeworms have evolved a specific behavioural pattern which results in regular, spaced-out settlement within aggregations, thus allowing room for each individual to become established and begin growing. By contrast, epiphytic bryozoans do not exhibit this kind of behaviour (Harvey, Ryland & Hayward, in preparation). Al-though a minimum size is probably required before the colony is able to breed, the pattern of growth observed for Alcyonidium hirsutum shows that this can be achieved through lability of growth direction. The linear relationship found to exist between colony size and fecundity shows that no advantage is conferred by increased size; the smaller colony is as effective in reproduction as the larger. In the present paper two other ecological consequences of aggregated settlement are considered: mortality and size.

Hydrobia ulvae has featured in many reports on the ecology of estuaries and mud-flats, yet surprisingly there are few detailed studies on population structure, growth and the breeding cycle. Population densities fluctuate widely from one locality to the next, and the variation in size recorded for the adults suggests significant differences in growth rate and the size at which the snails become sexually mature. The occurrence of Hydrobia in the stomachs offish and birds is well documented (Clay, 1960) and the suggestion that this species may influence the breeding success of some species of bird (Anderson, 1971) illustrates its importance in the ecology of estuaries and salt marshes.

During recent years attention has been focused on the morphology of the bivalve digestive gland (Sumner, 1966a, b; Owen, 1970; Pal, 1971,1972) but there is little information concerning its role in the storage of energy reserves. Reid (1969) has suggested that in the horse clam, Tresus capax, digestive gland lipid may serve as an energy store which is depleted when food is scarce. Sastry (1966) and Sastry and Blake (1971) have shown that material stored in the digestive tissue of Aequipecten irradians is transferred to the gonad during gametogenesis and Vassallo (1973) has confirmed the transfer of lipid in Chlamys hericia. The digestive gland of My tilus edulis may also have a storage function and may therefore be involved in the utilisation of reserves during starvation. The present paper deals with seasonal changes in the biochemical composition of the digestive gland of M. edulis, and with changes induced by starvation and temperature stress.

A number of species of the family Pectinidae (Lamellibranchia, Mollusca) are of considerable commercial importance in many parts of the world. Many of these are being reared in laboratories and hatcheries and this has made easier studies of cytogenetics using eggs and embryos, and ultimately will make studies of their genetics feasible. Recently, simple squash techniques have provided a fast and reliable method for obtaining chromosome numbers from eggs and embryos of several bivalves including Mercenaria spp. (Menzel & Menzel, 1965), Ostrea lurida and Crassostera gigas (Ahmed & Sparks, 1967), Mytilus spp. (Ahmed & Sparks, 1970), and Crassostrea spp. (Menzel, 1968). In 1967, Longwell, Stiles & Smith published the karyotype of Crassostrea virginica obtained from embryos which had been treated with colchicine.

Interest has developed recently in the biochemical composition of zooplankton, particularly in relation to seasonal changes. An earlier study (Raymont, Srinivasagam & Raymont, 1971b) on deep frozen Antarctic krill, Euphausia superba, collected over approximately 5 weeks in December/January 1968/69 suggested that protein was the main constituent and lipid much more variable. Despite the variability the mean lipid content during January was distinctly higher than in the previous month, thus supporting the findings of Kryuchkova & Makarov (1969) that lipid content of krill tends to increase as the summer advances. However, collections of material from the Antarctic have tended to be limited both in location and season while methods of preservation have varied. It seemed desirable to follow changes in the biochemical composition of krill collected from a somewhat wider area and over a longer period. Moreover, the more extensive material gave opportunity for a more detailed examination of specific fractions, such as the amino acids of Euphausia superba. Preliminary investigations (Srinivasagam, Raymont, Moodie & Raymont, 1971) on the amino acid composition of protein hydrolysates showed good agreement with the results of some other authors. However, the findings of Burkholder, Mandelli & Centeno (1967) and especially of Moiseev (1970) showed certain differences.