Oscular tubes were photomicrographed at intervals of roughly one or more days. The changes in length and width were determined using radiate spicules as markers. Changes in width were also measured directly using the outlines of the tubes. Several types of growth were thereby observed. The category considered here includes a temporary phase of constriction during the interval between the photographs. Such irregular growth is usual for Leucosolenia situated in rock pools on the shore.

During daytime low tides on the River Avon at Bristol, England, the exposed river banks become a deep green colour owing to the presence of enormous numbers of Euglena obtusa which emerge out of the black mud. Cell densities on the surface surpass 105 cells/cm2. Before the tide returns to cover the area, the cells re-burrow back into the mud and remain there during high tide and throughout the night.

The cells can be prevented from emerging on to the surface mud at low tide by artificially darkening the area with an opaque covering just as the tide recedes. Cells which are already on the surface can be made to re-burrow by similarly placing them in darkness.

The vertical-migration rhythm will persist in the laboratory in constant illumi-nation, constant temperature, and away from the influence of the tide, for nearly one month. In these conditions the rhythm is diurnal, rather than tidal. The rhythm will not persist in constant darkness.

Because of the excessive turbidity of Avon water, each high tide imposes a period of darkness on the surface mud. It is thought that these dark periods transform the fundamental diurnal rhythm into one of tidal frequency.

Various intensities of constant illumination alter the form and amplitude of the rhythm, but not the period. The stable nature of the period, under different light intensities, is thought to be due to a unique, self-stabilizing feature inherent in this type of rhythm.

The rhythm is inhibited at 2° C. Between 5° and 15° C, the period of the rhythm is virtually unaltered; it remains approximately 24 h in length.

The life-cycle of a population of Pandalina brevirostris living off the Northumberland coast is described. Most specimens were taken over sandy gravel or sandy mud with a covering of zoophytes in depths ranging from 20 to 30 fm. A very few specimens were taken over soft mud in 50 fm.

Eggs are laid during the period from January to the beginning of September. Females may lay two or possibly three broods in each breeding season. There is a period of 12–14 weeks between the laying of the eggs and the hatching of the larvae. The ova of those females that have a brood of eggs within the first half of the breeding season mature as the eggs develop, and are ready for laying following the release of the larvae. The adult P. brevirostris reaches maturity 8–12 months after hatching as a larva and lives on to breed again in the following season. They die at the end of their second breeding season. Thus, the probable life-span of the female is 24–30 months following its release as a larva, while that of the males is about 21–27 months.

Just before spawning the semen of the herring is isosmotic with the parent blood, the eggs are hyposmotic. Immediately the eggs are placed in sea water of salinities 5, 17·5, 35 and 50 %0 there is a change in the freezing-point of the yolk indicating that it has approached close to being isosmotic with the water. Changes in the freezing-point of the yolk during development indicate that the overgrowing embryo gradually regulates the osmotic concentration of the yolk, although full regulation is not achieved until after the closing of the blastopore. After this point there is no significant change in the freezing-point of the yolk or body fluids. Regulation is most probably brought about by the activity of the cells of the ectoderm.

Dead and dying fish were reported from the Moray Firth during a period of 15 days in September 1963. The initial mortalities were in the inner Firth, but they later spread outwards, especially eastwards along the southern shores of the Firth. Mass mortalities of the lugworm (Arenicola marina) also occurred in Scottish waters in 1962 and 1963, and at Balintorein Easter Ross fish and lugworm mortalities were contemporary.

Thin-layer chromatography has been used for the rapid separation of microgram amounts of pigments of marine phytoplankton, both from cultures and from the sea. The separation is carried out on plates coated with silica gel; the chromatogram is developed with a solvent consisting of petroleum ether (b.p. 60–80°), ethyl acetate and diethylamine in the ratio 58:30:12 by volume. The separated individual pigments may be eluted from the plate and characterized by their absorption spectra. The pigments of the following phytoplankton have been examined: Dunaliella primolecta, Phaeodactylum tricornutum, Isochrysis galbana, Dicrateria inornata, Coccolithus huxleyi, and Peridinium trochoidium.

Introduction

A knowledge of the component pigments of phytoplankton is of value in the systematic classification of these organisms and in the study of the mechanism of photosynthesis. Very little is known about the amounts of the lesser phyto-plankton pigments associated with the natural phytoplankton crop in the sea, but a considerable amount of work has been carried out on the measurement of chlorophylls a, b and c and of carotenoids for the estimation of the plant bio-mass in the sea. These determinations are usually carried out by modifications of the poly-chromatic spectrophotometric method originally described by Richards with Thompson (1952) and modified by Creitz & Richards (1955) (see also Parsons & Strickland, 1963). While these procedures give a satisfactory measure of chlorophylls a and b, their precision for chlorophyll c and carotenoids is poor; furthermore, no resolution of carotenes from xanthophylls can be attained; nor can any indication of the presence of unusual pigments be obtained.

An apparatus for sampling the fauna of the uppermost 10 cm of the sea is described. The net is designed to fish at speeds of 5–6 knots in undisturbed water to one side of a ship. A preliminary account is given of the catches made with the net in the Indian Ocean.

A description is given of an underwater camera unit mounted inside a high-speed tow-net body. The method of using this apparatus for surveying the seabed is described. The illustrations show that good quality results can be obtained when the camera is towed at speeds around 5 knots. By keeping the camera within a fathom from the bottom, satisfactory photographs can be obtained even where turbidity prevents photography at greater ranges.

Adult Pseudocalanus elongatus have been kept in the laboratory, and fed with a variety of algal grazing media. The survival under conditions of starvation has also been determined, and in this respect, the overwintering generation has been found to differ from other generations.

Isochrysis galbana, Phaeodactylum tricornutum, Gymnodinium veneficum, G. vitiligo, Chlamydomonas sp. and C. coccoides have been found to be satisfactory foods for Pseudocalanus elongatus

Dicrateria inornata, Nitzschia gotlandica, Amphidinium sp., Chlorella stigmatophora and Dunaliella tertiolecta were found to be unsatisfactory foods for Pseudocalanus elongatus.

The polychaete worms Cirratulus cirratus and Cirriformia tentaculata harbour a number of archigregarines which have frequently been confused in the past. An attempt is made to clarify the situation and a new parasite, Ditrypanocystis cirratuli, previously described only from C. tentaculata from St Andrews, is recorded from C. cirratus from Plymouth and described. The nomenclature of the archigregarines from C. cirratus is discussed.

The biochemical composition–water, glucose, soluble and insoluble glycogen, protein and non-protein nitrogen, total lipid–of the eggs of Balanus balanoides and B. balanus has been determined during development.

Preliminary analyses of the pigment content are reported.

The changes in both species are similar; but they take place more rapidly in B. balanus with its shorter period of embryonic development.

During development there is a net loss of all fractions; small increases of glucose and soluble nitrogen are, however, found at certain stages.

The pigment is largely a chromolipid; during the early stages of development this increases, but is subsequently lost; astaxanthin is also present. The visual appearance is a poor guide to pigment content.

The oxygen uptake of the eggs has been measured.

There is a discrepancy between the oxygen uptake measured directly and that required to oxidize the substrate lost; the causes of this are discussed.

The results are discussed relative to the habitats of the species.

The fecundity of 180 long rough dabs caught in the Clyde Sea Area from 1957 to 1961 ranged from 9700 eggs in a 12.2 cm fish to 251,300 eggs in one of 30.0 cm. The mean lengths of the fish in the samples each year were different so the comparisons between one year and another were based on the fecundity expected of a 22 cm fish. The differences between years were statistically significant, though successive years did not differ significantly when tested in pairs. The trends of increase and decrease in fecundity were very similar to those of the witch (and different from the plaice). It is suggested that, since witches and long rough dabs (in contrast to plaice) both prefer a muddy bottom, the fecundity variations from year to year might be caused by fluctuations in the abundance of some common food organisms.

Inactive Mn concentrations have been measured in lobster tissues. In the internal tissues of fresh animals, muscle contains 0.5–1.1 μg/g wet tissue, hepatopancreas contains 4.1–5.7 μg/g, excretory organs contain 2–5.5 μg/g and the blood contains 1.4–3.8 μg/g. Gill Mn concentrations are very variable and up to 30 μg/g are found. About 98 % of the Mn in the body lies in the calcified exoskeleton. Concentrations in the carapace are variable and are of the order of 100–300 μg/g of wet tissue. Possible ways in which the body Mn content may be controlled have been studied.

Manganese is lost from the blood during starvation and is absorbed so slowly from solution in sea water that normally an appreciable amount of the body Mn must be absorbed from food. Absorption from the stomach takes place via the hepatopancreas and the amount absorbed appears to be proportional to the Mn concentration of the stomach fluid. Similarly, there is no evidence that the slow absorption of Mn from solution in sea water across the gills can in any way be controlled and it may be a passive rather than an active process.

The structure of the thecae, as seen in the electron microscope, are described for two species of Prorocentrum and five of Exuviaella. For the first time it is possible to distinguish between true pores and the spines and thin areas of wall which have previously been described as pores or poroids. Several distinct features such as the spines covering the valves, the ridged valve margin and special flagella pore structures which are found in only two of the Exuviaella species suggest that it may be necessary to create a new genus.

The heart-body contains haematins derived from by-products of haem synthesis. It also contains a non-haem iron protein and a flavin. Study of the relative amounts of these substances in worms of different ages and at different seasons suggests that the flavin plays some part in the metabolic activity of the organ and that the haematins accumulate throughout life. No evidence was found for the heart-body participating in any excretory activity or in haemoglobin breakdown.

Data from nearly 900 individual herring sampled in the North Shields, Whitby and East Anglian fisheries during the period 1956–60 demonstrate a linear relationship between the percentage fat and the percentage water contents for whole herring minus gonads and gut content, and the fat/water line derived from the data is described.

The food and feeding habits, and general biology of the commoner gadoids in Manx waters have been studied. During the pelagic phase the diet of the gadoids showed a great similarity, consisting mainly of various abundant calanoid copepods. The larger pelagic post-larvae supplemented this basic diet with the inclusion of euphausiid ‘furcilia’ larvae and (in whiting) the amphipod Hyperia. Whiting, cod and pout were often found associated with medusae: the whiting, 21–53 nun long, were taken in large numbers, and their diet was found to be modified as a result of this association.

Young gadoids in a shallow sandy bay showed a great similarity in their basic diets, which typically consisted of various small, swarming mysids, amphipods and isopods. This habitat was a nursery area for many of the gadoids.

The larger fishes fell into two groups: (i) those that were characteristically feeders on the infauna and large, slow-moving epifauna; such fish being provided with stout barbels, well equipped with taste-buds, e.g. cod; (ii) those that feed largely, on the smaller active epifauna and nektonic prey, and possessed no, or only rudimentary, barbels, e.g. whiting.

The larger gadoids showed a concentration after spawning on a shallow, submarine shelf (the Warts Bank) to the south of the Isle of Man. Here the spent fish fed on an abundant and localized food, sand eels. The gadoids were found in this habitat from March to September, and were the object of a local fishery.

There was evidence that the gadoids exercised choice of food from that potentially available from the four primary food sources in each habitat; but if their favourite food was scarce or lacking, they would take substitute food by exploiting sources otherwise normally neglected.

The absorption of radioactive Cs from sea water in relation to K metabolism has been examined in the squat lobster Galathea squamifera. A general study has been made of the ability of Galathea to carry out osmotic and ionic regulation as a comparison with better known decapod crustaceans which have previously been used for radioactive Cs experiments.

Galathea appears to be a truly marine decapod in that it is probably unable to osmoregulate and the body surface is very permeable to water and to Cs and Kions. Despite this high permeability, Galathea is able to regulate K and radioactive Cs at blood plasma levels which are 1.3 and 1.1 times those of sea water. The Na and Cl concentrations in the plasma are not regulated and the Ca concentration is variable, but Mg and SO4 are maintained at concentrations below those of sea water. Urinary excretion does not assist in the conservation of K or radioactive Cs in the plasma but assists in removing Mg and SO4.

In North Wales settlement and metamorphosis of Balanus balanoides occur in May and the animals breed for the first time in the following November. Three weeks after metamorphosis the oviducal glands appear as epidermal invaginations in the basal segments of the first pair of cirri. At first there is no lumen or external duct but these develop during the next fortnight. The wall of the gland is a columnar epithelium which increases in height as the gland increases in size. During mitosis this epithelium exhibits the pattern of cell movements characteristic of similar epithelia in vertebrate embryos.

The chitin from pogonophore tubes is shown to be essentially the same as that from the pen of the squid Loligo and is classified as β-chitin (as are the known chitins in annelids). However, certain important differences in detail are seen when comparing X-ray diffraction photographs and infra-red absorption spectra of the chitin from the two sources. These matters are of interest in defining the systematic position of the Pogonophora as well as in reaching an understanding of the functions of the protective tube.