Concentrations of Zn have been determined in the tissues of normal lobsters from sea water containing about 5μg/1. of Zn. The blood usually contains about 6 μg/g of Zn, mostly in the serum, while the soft tissues contain between 10 and 50 μg/g. Long exposure to sea water containing 100/μg.g/l. of Zn fails to alter the Zn concentrations of the blood, muscle and gonads, but increases the levels in the urine, excretory organs, hepatopancreas and gills. This result suggests that extra Zn is absorbed from high Zn sea water, possibly via the gills, and that two methods by which this is removed from circulation are by urinary excretion and absorption by the hepatopancreas.

Changes in the blood Zn concentration produced by injection are rectified quite rapidly in the same way. Injections failed to change the Zn concentrations of muscle and gonads.

Further experiments showed that Zn can be absorbed rapidly from the stomach and reaches the blood partly at least via the hepatopancreas. Again, this extra Zn is removed from the blood by urinary excretion and by absorption in the hepatopancreas. Eventual removal of Zn in the hepatopancreas probably takes place via the blood and excretory organs rather than via the gut. The role of the gills and gut in the regulation of the body Zn content has not yet been studied.

The hydroid of the Anthomedusa Bougainvillia britannica Forbes has not been known with certainty, though its identity with B. flavida Hartlaub has appeared probable.

From colonies found on Aporrhais pespelecani in the Firth of Clyde medusae of B. britannica have been reared. A description and figures of the hydroid and the young stages of the medusa are given.

Bougainvillia flavida Hartlaub and B. linearis (Alder) are junior synonyms of B. britannica Forbes.

A method of line fishing in depths of over 1000 fm has been used successfully from R.V. ‘Sarsia’ on the continental slope. The catches have been mainly black squaloids but two brotulids, truly abyssal fishes, have also been taken.

By comparing the two species of Amphiura in controlled, directional bottom current flows, clear differences of behaviour can be demonstrated. These differences have been shown to be associated with two quite distinct feeding methods. Amphiura filiformis holds the arms up into the current flow with a rheotactic response to current direction and feeds by trapping both non-living particulate suspended matter and phytoplankton. Amphiura chiajei does not show this response and feeds exclusively on deposited matter on the sediment surface. Both species have modifications of the podia associated with the different methods of feeding. Estimates of growth rate, longevity and oxygen uptake suggest that Amphiura filiformis is a rapidly growing species with a high metabolic rate and food requirement, whereas Amphiura chiajei is slow growing and long-lived with a low metabolic rate. The environmental requirements of the two species are discussed.

Tubifex costatus is a marine euryhaline species of tubificid, commonly found in brackish water. It is common in estuaries, where it colonizes a wide variety of substrata.

The species breeds sexually once a year in early summer, and it is likely that it takes 2 years to reach maturity, and after breeding it dies.

There is only one likely predator, Nereis diversicolor, and the population of T. costatus seems to be kept at a very constant level.

The number of diatoms, and the carbohydrate and organic matter in suspension, were followed during most of the year 1962 in Loch Striven.

A rise in diatom numbers was always accompanied by a rise in both carbohydrate and organic matter, but the agreement was not quantitative.

The production of larvae by Ostrea edulis L. was studied in collections made from brooding females obtained from oyster grounds on the east, south and south-west coasts of England and from the Menai Straits. The size of the brood was directly related to the size of the oyster, but considerable variation was found from oysters of the same size whether measured as diameter, volume between the shells or dry meat weight. Part of the scatter was due to variation in condition of the oyster at spawning; oysters in good condition at the time of spawning produced more eggs than those in poor condition. This cause of variation was also seen in different populations; those with a high average condition index had a higher average fertility than those in poor condition, although the correlation was not quite significant at the P = 0.05 level (r = 0.632). It is presumed that most of the remaining variation is of genetic origin.

Fertility was related to size rather than age, although it is suggested that in some old slow-growing oysters it may be reduced. No decline in fertility was found as the breeding season progressed, nor was there clear evidence that larvae are liberated at a smaller size late in the season.

A comparison of the average size of broods at an early stage of development with those that were nearly mature showed that there was no loss of larvae during brooding. Samples of shelled larvae from 204 broods were measured; less than 10 % exceeded 190 µ size.

Ability to tolerate low salinities has been compared in homozygous adult females of the trifasciata and violacea forms of the polymorphic copepod Tisbe reticulata from Chioggia (lagoon of Venice). Both forms appear to be equally capable of tolerating sea-water concentrations of between 100 and 33 %. Further comparison with the trifasciata form of T. reticulata from Plymouth and with three different geographical populations of Tisbe furcata has shown that these copepods are rather less tolerant.

A study of ionic regulation using the isotopes 22Na, 42K and 137Cs has shown that in diluted sea water T. reticulata does not control the body Na concentration but does control the K concentration. Exchange rates for 42K and 137Cs are higher in the violacea than in the trifasciata forms of T. reticulata from Chioggia and the difference may have an adaptive nature although its significance is not clear. With regard to 42K, the difference between the two polymorphic forms from the same population of T. reticulata is greater than that between the three different geographical populations of T. furcata. This serves to add more emphasis to the fact that colour polymorphism in T. reticulata can be associated with other processes.

Experiments reported in a previous paper have indicated a considerable water loss by isolated preparations of the tube feet of Asterias rubens when ligatured in the protracted state. Because of its specialized structure, the podial diameter remains constant throughout the stepping cycle and this simplifies the procedure for measuring the surface area. Measurements of the internal hydrostatic pressure within the tube foot ampulla systems shows a maximum of about 30 cm water to be reached during the protraction phase of the stepping cycle, falling to nearly zero during the resting period. From these data it is possible to calculate a value for the permeability to water of the tube foot membrane, and such a value is compared with other membranes.

By measurement of the total area of protracted tube foot membrane exposed by the animal when supporting itself in sea water, it is possible to arrive at a figure for the total water loss by the water vascular system. For a 50 g animal this amounts to some 0·5 ml./h. Experiments involving blocking or extirpating the madreporite, and with isolated arms, make it extremely improbable that this loss could be made good from this route.

As alternative mechanisms, a slight hypertonicity due to the presence of excess potassium, or water movement as a direct consequence of the operation of an ion pump are discussed. In view of the hydrostatic pressure within the water vascular system the possibility of its functioning as a physiological kidney is also discussed. A possible alternative function for the madreporite is put forward.

After transplantation and acclimatization of populations of the barnacle Balanus balanoides from the coast of New England to the Menai Straits, differences in breeding behaviour persisted over a period of from 4 to 18 months. The two populations are believed to belong to distinct physiological races.

The New England populations fertilized 1½–3 weeks in advance of adjacent British populations.

Embryonic development in the post-cleavage stages of the New England population proceeded in vitro at about twice the rate of the development of the British population, under identical conditions.

The volume of the eggs of the New England population was 1.3–1.6 times as great as the volume of the eggs of the British specimens.

Both populations, when growing in British waters, liberated their nauplii in March at a time which coincided with the beginning of the vernal plankton increase in the locality. The embryos of the American population had therefore remained in the mantle space for a much longer period than had those of the British specimens and for a longer period than that reported for New England populations in their native habitat.

In B. balanoides the time of fertilization and rate of development may be genetically adapted in each general locality so that the embryos reach full term before the plankton increase is due. The actual time of liberation is then mediated by the hatching substance in response to prevailing food conditions.

If the B. balanoides population of the Western Atlantic area as a whole belongs to a physiological race distinct from that of the Eastern Atlantic, and responding differently to temperature levels at the breeding season, there is no reason to expect any close correlation in respect of environmental conditions between the southern limits of the species in Europe and in America.

When the oscular tube grows the spicules tend to separate from one another, but the separation is not uniform; local displacements of spicules occur with respect to other spicules in the vicinity. The same is found when the tube elongates while constricting, or changes shape in other ways. The spicule displacements reveal that the mesogloeal matrix is plastic. The spicules are probably anchored to the surface epithelia, the system of anchorage varying with time and from one spicule to another.

Small growing spicules may rotate through considerable angles and move relative to the fully grown spicules in their vicinity. The relative movements are most frequently towards the osculum. They are attributed to displacements of either the mesogloeal matrix or the internal epithelium, each relative to the other. They are not likely to be caused by the concerted amoeboid activity of the founder calcoblasts.

The monaxons tend to maintain their positions and orientations relative to the tri- and quadri-radiate spicules, apart from small localized displacements. Thus no significant movement of the pinacoderm relative to the rest of the wall could be deduced.

Fragments of broken spicules likewise tend to retain their relative positions and orientations in the spicule arrangement, though some moved or rotated by quite considerable amounts.

Spicules occasionally disappeared from the wall of some tubes. Monaxons were shed relatively easily, probably as a result of the spicule crowding associated with contraction of the tube. Some tri- and quadri-radiates were also shed through the pinacoderm. In some tubes spicule protrusion occurred at the oscular edge.

Measurements of cephalothorax length were made on the females of five species of oceanic copepods for the period from January 1958 through August 1959. The seasonal length variations of the three species of Pleuromamma (P. piseki, P. abdominalis and P. xiphias) followed the cycle in total phytoplankton. Significant positive correlations were obtained between the mean lengths of P. abdominalis and P. piseki and the mean quantity of phytoplankton of the month previous to sampling, but there was no correlation between length and temperature.

The seasonal length variations of females of Haloptilus longicornis and Lucicutia flavicornis differed in pattern from that of the Pleuromamma species and no correlation was found between their mean lengths and the annual cycles of phytoplankton or temperature. These species may feed selectively on some possibly unmeasured fraction of the plankton or on particulate organic matter.

Previous work has shown that in waters with a wide temperature range there is a high negative correlation between length and temperature and no correlation between length and phytoplankton. In other regions with an intermediate temperature range the sizes of successive generations of copepods are correlated to almost equal degree with the temperature and the quantity of phytoplankton available during growth. In the Sargasso Sea, where there is a narrow temperature range but a definite seasonal cycle in total phytoplankton, the length variations of the Pleuromamma species are correlated with the phytoplankton cycle and not with temperature.

The seasonal fluctuation in numbers of C. tentaculata was investigated from December 1959 until February 1962. The lowest numbers were recorded in April followed by a rapid increase in numbers during May. The magnitude of the increase varied from year to year, as also did the number of peaks that occurred during the summer months.

The worm was shown to have an extended breeding season from the end of March to September during which several spawning ‘bursts’ took place. Experiments suggest that some spawning may occur when the mudflat is inundated by the rising tide, although spawning was not observed in the field.

The population of C. tentaculata exhibited an annual cycle of growth which was influenced by the seasonal variation in temperature. Laboratory observations suggest that a temperature of about 20° C is optimal for the growth of young worms. The growth rate (8 mm/year) is slow compared with that of other polychaetes.

It is tentatively concluded from the field mortality data that between 10 and 16 % of animals survive to an age at which they are sexually mature; between 6 and 8 % of each generation reach an age of 15 months. Causes of mortality in the population are briefly discussed.

By estimating samples of diatoms taken from 0.2 m contour lines, over a horizontal range of about 85 m in the months of July 1953 a nd February 1954 the ecological factors influencing the distribution of eleven species of mud-flat diatoms were investigated. The three important factors were considered to be: the resistance to desiccation near the M.H.W.L., the ability to live under short periods of illumination near to the M.L.W.L., and the ability to tolerate the organic materials present in the black sulphureous layer. Table 7 summarizes the results for the eleven species.

Laminariocolax tomentosoides is a common epi-endophyte on the I.O.M. Though probably pseudoperennial as an endophyte it produces fertile external filaments only from September to June with a March maximum in size and numbers. It reproduces vegetatively by growing through its host's tissues and asexually by means of zoospores from plurilocular sporangia. In culture, zoospores give rise to fertile plants in 7 days and several generations can be produced in 4 weeks. The offspring bear only plurilocular sporangia. The chromosome number is apparently 16 and the life-history probably a postponed series of diplonts.

Laminariocolax tomentosoides produces cysts which, in the past, have been mistakenly identified as unilocular sporangia and which are so similar to the ascocysts of Ascocyclus that this genus would seem to be based on a character of little value. Another description of unilocular sporangia in the species is tentatively attributed to infection by a fungus.

Some ecological data concerning the Plymouth species of Leucosolenia are given, together with a discussion of the speciation of the British Leucosolenia.

Oscular tubes of L. variabilis have been photomicrographed at intervals, usually of 1 or more days. It was found that the choanoderm boundary at the proximal end of the oscular rim may advance, remain stationary, or recede in relation to the distal edge of the tube, according to the conditions. It may also move in either direction in relation to the spicules in its vicinity, regardless of how it is moving with respect to the oscular edge. The evidence indicates that the choanoderm is mobile on the inner surface of the tube and that the level of the choanoderm boundary is influenced by the surface area available and by the rate of multiplication of the choanocytes. The former depends upon the degree of contraction or expansion of the tube and the size and number of pores.

The arrangement of the choanocytes can alter within a few minutes. The cells, however, tend to cohere; their outlines near the base are polygonal and there is a thin hyaline layer separating the surfaces of adjacent choanocytes.

The beating of the flagella is uniplanar, the plane being perpendicular to the wall. The frequency of the beat varies from one choanocyte to another, as does also the orientation of the plane of beating. The latter does not alter when a current of water is drawn across the choanoderm. Excision of an oscular tube results in water flowing out at both ends as soon as the cut has been opened.

Analyses have been made of some of the constituents of the coastal sea water and the river water, and the results have been correlated with the growth phases of some planktonic diatom species and littoral epiphytes, although for most species the sea-water temperature and light intensity were limiting factors.

The factor determining the death of an epiphytic diatom community in the littoral zone has been considered to be the air temperature in conjunction with desiccation and a summary of the limiting temperatures for each of the four substrata is given in Table 7. Table 10 is a summary of all the distribution and temperature records. The heat itself is not lethal in many cases but the desiccation of the epiphyte in the littoral zone is accelerated at higher temperatures. Diatoms in damp situations were found to occur at temperatures which in a dry site were limiting, and further work indicating the relationship between relative humidity and lethal temperatures is needed.

The ability of a diatom to survive depends upon the water-retaining ability of the substratum. Chalk and large algae favoured the growth of most solitary epiphytes, and filamentous epiphytes grew particularly well on algae except the filamentous Navicula, which were best suited by chalk. The Achnanthes blue-green community was most frequent on wood. Concrete makes a firm substratum and allows rapid growth in winter but it is easily dried and most diatoms on it are destroyed in the summer.

Four diatom genera (Fragilaria, Grammatophora, Biddulphia and Melosira) are able to exist in the epiphyte flora and the shore plankton and the term facultative epiphyte is suggested to describe the behaviour of at least some of the species of these genera.

Larvae of the sand-eel, Ammodytes marinus, appear in large numbers in the Southern Bight during March, some 2–4 weeks after the peak hatching period of plaice eggs. The sand-eel larvae outnumber those of the plaice about tenfold, but the factor may be 60 or more locally.

The principal food components in sand-eel guts in 1961 were copepod nauplii and appendicularians, while plaice were feeding almost exclusively on the latter. Larvae of both species show identical feeding patterns, with activity ceasing at night, and both aggregate during the day at depths of about 2–6 fm. Thus the sand-eel larvae are not separated from the plaice larvae by any pattern of behaviour, and are partially exploiting the same food reserve.

Consideration of prey size suggests that any direct competition from the larval sand-eels would first affect the smallest plaice larvae, which are in any case the most vulnerable to shortage of food. But any reduction in the crop of small appendicularians will later be reflected in the number of larger ones, and in this way older plaice larvae might be affected. While the food supply appears to have been adequate up to the time of the investigation, the reserve apparently represented only 3 days' rations. The significance of this observation is unfortunately obscured by our ignorance of appendicularian biology; but, should the food reserve become so diminished, competition between plaice and sand-eel larvae might be expected. The extent of its impact on survival is only likely to emerge from more comprehensive surveys.

Assays and mixed culture experiments prove that the supply of chelating substances is frequently the most crucial aspect of phytoplankton nutrition in sea water. Experimental results, theoretical considerations and tentative calculations show that this supply is controlled by the stability of the trace metal chelates and in the sea may be mediated by certain unknown minor components of the dissolved organic matter.

The results of Parts I and II are considered together and show how seawater quality is closely related to the chelation of trace metals, mainly iron, and various other factors previously listed in the summary to Part I.

Five cyphonautes are described in Nordisches Plankton (Lohmann, 1911). Cyphonautes schneideri and C. borealis are larvae of Membranipora membranacea and represent extremes of variation in the shape of the shell. Cyphonautes balticus, like C. compressus which was very inadequately described, is the larva of Electra pilosa. The cyphonautes of these two species are the only ones likely to be encountered in the plankton of normally saline European seas. Cyphonautes barroisi is the larva of the brackish-water Electra crustulenta.

Cyphonautes balticus Thorson (1946), not Lohmann, is the larva of M. membranacea.

Larval synonymies for M. membranacea and E. pilosa are given.

The use of the Cyphonautes names is undesirable, and those of the polyzoan adults should be employed.