The life-histories of the erycinaceans Montacuta substriata and M. ferruginosa were investigated with special reference to the initiation of their ‘commensal’ associations. The planktotrophic larvae are released in summer as veligers after incubation within the adults, and they may spend several months in the plankton before settlement and metamorphosis. Larvae of both species, isolated from the Plymouth plankton, were reared to post-larval stages that were comparable with spat found associated with spatangoids. Some corrections are made of the identifications of planktonic larvae, of these and other Erycinacea, by previous authors. Experiments showed that, apart from being more active, the responses of walking post-larvae are similar to those I have described previously with adults. It is considered that the reactions operate, in an integrated manner similar to the adults, in initiating their associations with spatangoids; the behaviour of the adults in maintaining and re-establishing their associations would thus represent a retention of larval faculties. Possible reasons for the restriction of M. substriata to superficial burrowers and the less specific occurrences of small M. ferruginosa amongst spatangoids—including both deep and shallow-burrowing species—are discussed.

Observations were made on the feeding and respiration of the common small copepods in the Clyde sea-area, using cultures labelled with P for feeding experiments and the Winkler method of oxygen determination for respiration measurements.

The development of an ellobiopsid parasite,Thalassomyces fagei (Boschma), within the cephalothorax of an euphausiid,Thysanoessa raschi (M. Sars), is described for the first time. The tissues of the young stages of the parasite have no intimate connexions with those of the host but become fused with them when the trophomeres begin to differentiate into a series of gonomeres. The parasites are found inT. raschi but have not been found in recent years in the associated population of the euphausiid,Meganyctiphanes norvegica (M. Sars), although it was recorded in one specimen of this species in 1925. The older stages of this parasite only occur inT. raschi in the Clyde during the period March-June but they have been recorded in the same species and other species of Northern Atlantic euphausiids in other sea areas later in the year. No fresh evidence has been found to decide whether these parasites have dinoflagellate, rhizopod, or fungal affinities.

Consideration has been given to the cell diameters of twenty-four samples of Rhizosolenia styliformis var.oceanica from a wide range of latitude together with material from eleven other collections already briefly recorded in Part II of this paper.

It was found that the cells of the smallest diameter occurred in high latitudesand that the average values were greater at lower latitudes.

More auxospore generations were present simultaneously in higher latitudes. An interpretation of these observations is that the prevalence of smaller cell diameters and the simultaneous presence of more auxospore generations in high latitudes could be due to relatively lighter grazing by herbivorous zooplankton in these regions.

Measurements of a few samples of a form of Rhizosolenia styliformis (Bright-well) which I called var. oceanica have been published earlier (Wimpenny, 1946), and auxospore formation was recorded from the Faroe-Shetland area. Since that time, owing to the kindness of the late Dr Vedel Taning, I have been able to see sixteen samples taken in the North Atlantic by the Danish research ship 'Dana' in1948. Mr J. Corlett of the Fisheries Laboratory, Lowestoft, has also been good enough to have made available to me three collections containing this variety from the Weather Ships 'Jig' and 'Item' in 1950 and two from the west ofBear Island in 1952. Finally, I have to add two samples of 33 and 50 specimens fromthe northern North Sea area made available to me many years ago by the late Miss Ogilvie and another sample from which I have been able to measure 100 specimens givenme by Dr James Fraser (E 34, 1934).

Cod (Gadus morhua L.) from the Arcto-Norwegian stock that spawns off northern Norway were caught at various times during the course of their gonadal maturation cycle, and plasma samples were collected for the determination of vitamin A compounds and lipids.

The main changes found concerned vitamin A aldehyde, which increased from a resting level of2μg/100 ml. plasma for adult females caught in September to 10 μ/100 ml. in ripe females caught in January-March approaching their spawning grounds; by contrast little change was observed in the males. In the fish of both sexes caught in September, just prior to the onset of maturation, dehydroretinal formed about 38 % of the total aldehyde, but in the plasma of ripe females the proportion was only 16 %. In both sexes there was a fairly steady decline in the levels of vitamin A esters and alcohol in the plasma during the winter. Similarly, the concentration of plasma lipids fell during the winter in the male cod, but in the adult females, during the period of ovarian maturation, the concentration of lipids increased and was maintained at about 0·5 g/100 ml. higher than in the males; in spent fish the concentration of lipids fell to the same low levels in both sexes.

It was considered that the changes in vitamin A aldehyde, and also of blood lipid, in the females were directly linked with sexual maturation, these compounds being transported to the developing eggs in the ovary. On the other hand, the general decline of vitamin A esters and alcohol in both sexes, and of lipids in the males, was probably due to the obligatory winter starvation which occurs in this stock.

Detailed sampling of the bottom water of Christchurch Harbour, England, was undertaken in conjunction with a study of the living and dead foraminiferids (to be described later). The Harbour is a shallow estuary with an unusual tidal regime of four high tides daily. During the winter the flow of fresh water from the rivers prevents sea water from entering much of the estuary. During the spring, summer and autumn, when drier conditions prevail on land, the sea enters the estuary as a salt wedge and there is pronounced salinity stratification. In addition to determinations of chlorinity, pH, dissolved oxygen and temperature, analyses of calcium were made during the spring, and of calcium and magnesium in the summer. It was found that calcium was preferentially removed from the bottom water, thus upsetting the calcium-chlorinity ratio. The cause of the calcium removal is thought to be biological activity. Magnesium was not affected by this process. A discussion of the results is presented and it is suggested that biological removal of calcium from the bottom water is particularly well developed in Christchurch Harbour owing to the extensive areas of shoal water favouring biological activity. Estuaries of this type may not be very common.

An account is given of the distribution of certain polysaccharides, lipids and proteins in the tissues of Siboglinum atlanticum, a uni-tentaculate pogonophore collected from depths of 1300–1500 m on the continental slope. The histology of the various glands and cells is described, and the structure and histochemistry of the tentacle compared with that of three multitentaculate species of pogonophores collected from similar habitats.

Esterases hydrolysing a naphthyl acetate and o-acetyl-bromoindoxyl are found in most tissues of Siboglinum after formalin fixation. An eserine-sensitive esterase was present in the dorsal ciliated band, mostly close to the bases of the cilia. An organophosphorus-resistant esterase was widely distributed as scattered particles in the subcuticular region of the epidermis of the tentacle and anterior end. The other tissues, including the epidermal glands, blood vessels, muscles and peritoneum, contained a simple B-esterase which was closely associated with lipid globules; the nerve fibre B-esterase was not associated with lipid and its apparent sensitivity to copper illustrates one aspect of the difficulty of applying mammalian esterase subdivisions to invertebrates. Lipids form the main food reserve, and appear to have a dominant role in the metabolism.

Pogonophores do not possess a gut at any stage in their life, and must take up food through the epidermis, whether or not it is first digested. The epidermal glands do not appear to have any digestive function. The multicellular pyriform glands secrete fibres of chitin and acid mucopolysaccharide, and produce the major part of the tube in which the animal lives. The unicellular glands are of several types, but most of them, apart from some simple mucous glands, appear to take part in tube formation, secreting mucopolysaccharides or mucopolysaccharides and protein.

The tidal rhythm of migration of the mud-fiat diatom community is a curtailed diurnal rhythm. Evidence is given of the similarity of these two oscillations in the laboratory and in the natural conditions of the estuary. However, the interference of the diurnal rhythm by water or stirring results only in one repeated rhythm on the following day; thereafter the migrations revert to a day-length-induced synchronization.

In simple choice experiments Protodrilus symbioticus Giard, an interstitial archiannelid, was shown to prefer the sand from its habitat in the natural state to the same sand altered by various physical or chemical treatments. The attractiveness of a sand was measured as the ratio of the number of Protodrilus entering the experimentally treated sand to the number entering the natural sand in simple or multiple choice experiments.

The attractiveness of natural sand to P. symbioticus could be destroyed almost completely by acid cleaning, by heating in water above 50° C or by drying at any temperature.

Treating attractive sand with formalin or cetyltrimethylammonium bromide rendered it about half as attractive as before treatment. Heating natural sand in water to 40°C and keeping it in fresh water for 18 h had no effect on the attractiveness. Sands that have been made unattractive by acid cleaning or drying can be restored to an attractive state by soaking in sea water. Typically acidcleaned sands recovered up to half and dried sands almost the whole of the attractiveness.

Inoculation of naturally occurring sand bacteria to highly unattractive acid-cleaned sand restores the attractiveness completely. Autoclaved sand to which a culture of Phaeodactylum had been added was preferred to sand treated with cultures of Dunaniella and Chlorella. An ordinary culture of Phaeodactylum contaminated by bacteria restored the attractiveness to autoclaved sands more effectively than a bacteria-free culture.

Sands restored by inocula of natural sand bacteria, soil bacteria and Pseudomonas sp. were preferred to those treated with Corynebacterium erythogenes, Flavobacterium sp. and Serratia marinorubra and these were preferred to control sands kept in sterile sea water.

The metabolic or respiratory rate, measured as the aerobic oxygen uptake, of the limpets Patella vulgata L. and P. aspera Lamarck was determined over a range of temperatures in January and in July. In order to determine the effects upon metabolism of adaptation to habitat, P. vulgata living at high shore levels were compared with those living at low shore levels.

The respiratory rate is proportional to the power –0·3042 of the fresh body weight and the relationship is not affected by temperature or season, and is the same for both species.

There is very little difference in the rates of respiration of equal weight individuals of P. aspera and either group of P. vulgata in January. In July the respiratory rate of low-level P. vulgata and of P. aspera is higher than in January whilst that of the high-level P. vulgata is little changed.

The Q10 of respiration had a low value between the temperatures of 15–20° C in both species, and this is thought to represent a hitherto unrecognized form of acclimation to maintain metabolic constancy over the mean environmental temperature range. In P. vulgata low values of Q10 were correlated with high environmental temperatures. Lower Q10's were recorded in July than in January and, in addition, limpets which were adapted to the elevated temperature of high shore levels in July had lower Q10's than the limpets from low shore levels. This apparent acclimation of Q10 was not observed in P. aspera.

The significance of the differences in metabolic rate and in Q10 are discussed in relation to acclimation and its importance in the ecological distribution of the two species.

A 250 ml. chemostat has been used to measure the parameters of vitamin B requirement in the chrysomonad Monochrysis lutheri.

The yield constant was ca. 0·25 × 10 cells/μμg., i.e. one-third of the figure previously measured in batch cultures.

The saturation constant lay between 2 and 6 μμ/ml., i.e. at least twenty times the figure indicated by previous batch culture measurements.

Internal inconsistencies in the chemostat's operation indicate the presence of factors not accounted for by theory.

It is argued that only factors analogous to the release of protein-bound vitamin into the medium could in principle account for all the discrepancies.

Nannochloris oculata Droop, an obligate phototroph, has no absolute nutritional requirement for any organic compounds. However, no growth takes place in neutral media lacking base, due to the lengthening of the initial lag phase. Weak acids shorten the lag even though pH has not been altered. The lag is interpreted as the time taken for the cells to excrete sufficient weak anions to lift the carbon dioxide in solution to the minimum required for growth. Glycollate excretion is discussedin the light of this interpretation.

Thirty-nine strains of (mainly) supra-littoral algae were tested for their ability to utilize glycollic acid for chemotrophic and phototrophic growth at the' natural' pH of 8.c. In no instance was there convincing evidence that glycollate either supported growth in the dark or enhanced the growth rate in the light in the presence of carbon dioxide, although acetate performed one or both these functions in a number of the strains. It was concluded that glycollic acid was unlikely to serve as a significant carbon substrate in neutral or slightly alkaline habitats.

A survey has been made of reflecting layers in the integument of selected fishes, including silvery sea lamprey and various silvery and partially translucent teleosts. Lamprey and juvenile rockling have only a stratum argenteum. Other silvery teleosts have a layer of oriented reflecting platelets lying outside the stratum argenteum; these lie more or less parallel to the vertical to the surface of the water.In dace, herring, and salmon parr the platelets on the upper flanks are tipped slightly upwards; but in some pelagic fishes, e.g. the mackerel and gar-fish, the platelets here are tipped downwards. Smelt, sand smelt, half-beaks, found in shallow or coastal waters, are partially translucent, partially silvery. The implications of these arrangements of reflecting layers are discussed. Both in clear oceanic waters, away from the surface, and in shallow or turbid rivers or ponds, light is distributed almost symmetrically about the vertical to the surface, and the greatest intensity is directed downwards. Under these conditions the reflecting layers diminish thevisibility of the fish from most fields of view because they reflect light approximately equal to the background light against which the fish is seen. On the lower flanks, when the surface is sloping, the reflected light tends to be spread and to beless intense than the incident light. Thin fishes, dark above with vertically reflecting sides, are effectively camouflaged except for the ventral extremity. The lower flanks of tapering or rounded fishes are well camouflaged by reflexion from below and behind because the platelets slope inwards towards the tail, and the projected area of incidence relative to reflexion is thereby increased.

Nautilus macromphalus Sowerby when freshly caught was close to neutral buoyancy having a weight in sea water of about 0–2% of its weight in air. The animals without their shells varied considerably in density but the volume of the shell was an approximately constant fraction of the total volume of the whole animal and whole animals were brought approximately to the same density by havingmore or less liquid inside the chambers of the shell. About 80 % of the gas space in the shell was used to support the weight of the shell itself in sea water.In an adult animal the centre of buoyancy was found to be about 6 mm above the centre of gravity, which made the animal very stable in its natural swimming position, a couple of about 350 g. cm being required to turn it through 90°. The pearly partsof the chamber walls were impermeable to sea water but the chalky and horny siphuncular tubes joining the septal necks were very porous. The most newly formed tenor so chambers were the only ones to contain liquids in appreciable volume and theydid this in diminishing amounts from the newest to the oldest. The watery liquids found within the chambers were always hypotonic to sea water and sometimes markedly so; they contained principally sodium and chloride ions. One animal was in the process of forming a new chamber, this incomplete chamber was completely full of liquidwith an osmolarity close to that of sea water but differing in composition from seawater.

The Council records with regret the deaths of Mr Morley H. Neale, C.B.E., Dr M. N.Hill, F.R.S., Prof. W. F. Whittard, F.R.S., and Prof. Hans Pettersson, For.Mem.R.S. Mr Morley Neale had been a member of Council on a number of occasions, a Vice-President of the Association since 1951, and by a gift made in 1958, he founded the Morley Neale Fund for 'the benefit or pleasure of the Plymouth Laboratory staff and ship's crews'. Dr Maurice Hill had for many years been associated with the life and work of the Laboratory and its ships. He first served on the Council in 1956 and was a member at the time of his death. Prof. Whittard had served on Council for two periods and in recent years had made a number of cruises in 'Sarsia' in the course of his investigations of the geology of the sea floor in the western English Channel. Prof. Hans Pettersson was elected an Honorary Member of the Association in 1949 and was at the time of his death second in seniority of the nine Honorary Members.