No general description of the Plymouth Laboratory of the Marine Biological Association of the United Kingdom has been published since that of Allen & Harvey (1928). Some information was, however, given by Russell (1947, 1948) in a survey of the work of the Association, and detailed accounts of the old and new aquarium and sea-water circulations were written by Wilson (1952, 1960).

Since 1928 there have been very considerable alterations and additions to the laboratory and, now that the major building extension has been completed, the time is opportune for a new descriptive account of the buildings and research facilities.

The difficulty of keeping planktonic organisms alive in captivity has greatly hindered experimental studies of their physiology and behaviour. This has especially been the case with the plankton of the deep sea. Up to the present our studies of these organisms have been largely morphological and distributional and it is clear that to learn more about their ecological relationships we must find means of keeping them alive to study their metabolism and behaviour experimentally. With this end in view attempts have been made to keep some oceanic plankton animals alive in the laboratory on board ship and ashore.

One of the most fundamental problems of oceanic ecology is the study of spatial and temporal changes in plankton distribution and the elucidation of the factors that govern them. A prerequisite of such work is that the tech- niques of sampling should be of sufficient accuracy to allow real changes in distribution to be detected and expressed in quantitative terms. The difficul- ties of fulfilling these sampling requirements are formidable even for the smaller plankton organisms, but a number of reliable and accurate quantitative samplers do exist for animals in this size range. For the larger zooplankton and smaller nekton, however, the lack of suitable sampling gear and methods has to a great extent restricted our knowledge. While the use of large conical nets and trawls at all depths over a wide geographic range has produced a vast body of data on the systematics of the major groups of macroplankton, there is little precise data on the depth distribution of even the commonest forms and only the vaguest estimates are available as to their relative abundance. The lack of more precise data can be attributed to two major technical deficiencies, first, the absence of efficient and reliable methods by which large nets can be opened and closed at depth, and secondly, the lack of accurate depth monitoring equipment. This paper describes the preliminary results of work aimed at meeting the first of these requirements but reference will also be made to the use of an instrument that represents a major advance towards serving the second.

In the past few years considerable attention has been paid to the distribution of the microflora of the salt marshes at Gibraltar Point, Lincolnshire (National Grid reference TF 555576). During these studies it was observed (Turner, personal communication) that blue-green algae (Myxophyceae) were of frequent occurrence in soil samples from the region, but no analyses of the algal flora were carried out. It is well established, however, that blue-green algae are generally present in salt marsh regions (Chapman, 1960 a). Previous studies on the blue-green algae of British salt marshes are few, although detailed investigations have been carried out at Canvey and Ynyslas (Carter, 1932, 1933 a, b) and Scolt Head Island (Chapman, 1939). Some difficulty is experienced, however, in attempting to correlate these results with present day studies, mainly because of the widespread colonization of salt marsh regions within recent years by Spartina townsendii H. & J. Groves, and by the fact that few quantitative data are available. It is hoped that the present communication which is concerned with the blue-green algal flora of the New Marsh at Gibraltar Point, a region dominated by Spartina townsendii, will allow an assessment to be made of the flora prevailing in a developing salt marsh under present-day conditions.

It was recently suggested (Boney & Corner, i960,1962a) that, contrary to the theory of complementary chromatic adaptation, the accessory pigment phycoerythrin might not be involved in photosynthesis by sporelings of the intertidal red alga Plumaria elegans (Bonnem) Schm. but is used primarily as a means of protecting the plant from excess green light in the wave-band 500–540 mμ. This work, however, was done with one species only, and concerning the wider question of marine red algae in general, it seemed possible that the role of phycoerythrin might vary with ecological distribution. Thus, plants completely submerged and thereby excluded from most red light would use their accessory pigments for photosynthesis (energizing chlorophyll a indirectly); but plants adapted to long periods of normal daylight would be similar to Plumaria in relying to a much greater extent on chlorophyll a alone for photosynthesis, and use their accessory pigments as protection against inhibitory green light.

A series of nine plankton cruises was completed by the research ships ‘Sir Lancelot’ and ‘Platessa’ in the spring of 1954 to study the ecology of a patch of Calanus finmarchicus (Gunner.) off the north-east coast of England. This paper will deal with the problems encountered in identifying such a patch over the period from 19 March to 4 June 1954.

Algal productive rates have rarely been estimated at sea, although many estimates have been made of primary productivity as g carbon/m2/day. A distinction may be drawn between productive rate and productivity, and it is in the use of the term ‘standing stock’. The latter is the quantity of living algal material per unit volume or beneath unit surface. The productive rate is the rate at which the standing stock reproduces itself; for a given species it is of course a division rate. It is expedient to use the term ‘division rate’ for a single species, but the term ‘productive rate’ may be used for the whole algal community. The productivity is the product of standing stock and productive rate and so contains in it the very great variations of standing stock that are the common experience of all planktologists.

The purpose of this paper is to assess the grazing capacity of Calanus finmar-chicus (Gunner.) in terms of the quantity of food eaten in the sea. The part played in the growth of the animal by the quantity eaten will only be briefly discussed. The parts played by nutrient lack, sinking and diffusion on the algal productive rates will also be discussed, leading to the conclusion that grazing mortality is the most effective controlling agent on algal production.

A subsidiary purpose of this paper is to relate changes in the weight of Calanus finmarchicus to changes in food consumed and to changes in water temperature. Measurements of C. finmarchicus have been made by a number of workers (Adler & Jespersen, 1920; Russell, 1928; Marshall, 1933; Stormer, 1929; Bogorov, 1934; Jespersen, 1939; Clarke & Zinn, 1937). It will be shown that in the North Sea, in spring, the greatest changes in weight are most readily related to changes in quantities of food consumed.

The part played by nutrient salts in the study of marine productivity is well known. When this series of production cruises was being planned, it was decided to take observations of the quantities of different nutrients in the sea. The cruises were closely spaced in time in order to provide an opportunity for examining the fairly rapid changes in nutrient content in relation to algal numbers. Nutrient observations were not made at such frequent intervals of time, because the spectrophotometer could not be used from R.V. ‘Platessa’. On ‘Sir Lancelot’ it was found that the spectrophotometer could be used adequately only when the ship was steaming before the wind and constituted a stable platform; this limit, however, reduced the opportunities for sampling nutrients in the desired positions.

Thirteen cruises were made between mid-March and early June in 1954 off the coasts of southern Scotland and north-east England. It is likely that a Calanus patch was followed continuously during this period merely by observing the abundance of Calanus in and out the patch at very short time intervals (5–8 days between the mid-points of the cruises). Fig. 3 in Cushing & Tungate (1963) shows the distribution of Calanus copepoditestages during the period, which is the sort of picture expected if the same population were being sampled during the period. Application of the Joseph & Sendner (1958) equation suggested that the reduction of density due to diffusion was likely to be very low.

The fecundity of Clyde plaice, which has been studied from 1956 to 1961, has not been found to change as the breeding season approaches. However, there was a marked fecundity change from about 137 thousand eggs to around 161 thousand after 1957. The fecundity of all age groups increased and this appears to be associated with the fishing intensity and so the population density. Heavy fishing leads to fewer fish with the same food supply which in turn allows higher fecundity. The changes in fecundity therefore seem to be part of a density dependent population regulating mechanism.

The fecundity of Clyde witches was estimated from 1958 to 1962, and has been found to vary from over 49,000 eggs for a 26·8 cm fish to more than 599,000 in a 42 cm witch. Annual variations in the fecundity were found but there are not sufficient data to relate the changes to the population density as can be done with plaice. It appears that Clyde witches may grow faster, and they certainly attain a larger size than those in the Irish sea.

Synthetic analogues of natural metabolites (antimetabolites) have been used to assess the sensitivity to inhibition of marine unicellular algae in laboratory cultures and also of more open-sea species grown in mixed culture in nutrient enriched sea waters. Different species show a different pattern of response to a range of antimetabolites. The presence of vitamins and metabolites in the medium influences inhibition of a species by an antimetabolite. The extent by which various sea waters influence inhibition is perhaps capable of development as a measure of the natural metabolites present. Species which are related or which occur together in the sea at the same time of year tend to show similar patterns of response. It is suggested that there may be a connexion between the susceptibility of species to antimetabolites and phytoplankton ‘succession’ in the sea.

Preliminary culture assays were made using marine algae to elucidate the ‘quality’ of sea waters from the North Sea and North Atlantic Ocean for phytoplankton growth. Assays with (a) bacteria-free Skeletonema costatum, (b) unialgal Skeletonema and Peridinium trochoideum and (c) mixed phytoplankton organisms indicated change of quality according to location, depth and season. Assay results correlated best with zooplankton indicator quality and to a lesser extent with phytoplankton abundance. Assay results were also compared with the distributions of temperature, salinity, oxygen, phosphate, U.V. fluorescence, phytoplankton dominants, zooplankton dominants and abundance. Assessment of sea-water quality was biased for the assay organism used. Factors which altered sea-water quality were added thiamine and B12 (40% improved), IAA (25% improved) and EDTA (almost invariable manyfold improvement). Destructive chemical treatments removed almost completely any good qualities for growth of Skeletonema but seldom for that of Peridinium.

The history of the medusa Tiaranna rotunda (Quoy & Gaimard) is reviewed. Little has been published on its young stages and its hydroid is unknown.

Young specimens of the medusa, caught in the Firth of Clyde, are described and figured.

The species Modeeria formosa Forbes is discussed and is shown to have been described from a young specimen of Tiaranna rotunda. By priority the specific name becomes Modeeria rotunda (Quoy & Gaimard), and Modeeria Forbes becomes a senior synonym of Tiaranna Haeckel. The family name Tiarannidae is unchanged. The type-genus is Modeeria, of which the typespecies is M. rotunda.

The seasonal occurrence of the medusa is discussed and evidence is adduced supporting the belief that the species is specialized for living in deeper water.

On British shores Pylaiella littoralis occurs in a large number of local populations which usually fall into one or other of four population groups. These populations often differ in habit, form, seasonal distribution, etc.

Two populations of P. littoralis from different environments have been studied experimentally and it seems from this that the morphological differences between the plants from the two populations are accompanied by physiological and genetical differences. Similar results have been obtained from experiments on other populations.

It is suggested that the numerous populations arise through the selective effect of all the prevailing environmental factors and are adapted to them.

The potentially large number of plant forms resulting from this process should not be described in terms of ‘orthodox’ taxonomy though they may possibly merit definition in terms of ‘experimental’ taxonomy in so far as some of the populations may constitute ecotypes as recognized in higher plants. Because it is possible for a single ecotype to be represented by more than one morphological type, however, the value of the ‘experimental’ system is regarded as doubtful.

Amino acids, both free and combined as protein, and some other nitrogenous constituents of Calanus finmarchicus have been examined. Seventy-six per cent of the total nitrogen in C. finmarchicus was present in protein amino acids, 14% in the free amino acid fraction, 6% in trimethylamine oxide, and 1·5% in betaine. These findings are discussed in relation to previous work on nitrogenous constituents of Calanus.

The free amino acid fraction of Calanus is compared with that of higher Crustacea and it is suggested that this fraction may be important in the adaptation of the animal to dilute sea water.

Amino acid nitrogen made up 40% of the total nitrogen of particulate material from Clyde sea water. This finding is compared with other recent analyses of the phytoplanktonic nitrogen and total particulate nitrogen of inshore waters.

The amino acid composition of adult female Calanus helgolandicus Claus and particulate material at station L4 has been analysed from March to December. The average concentration of amino acid nitrogen in Calanus was 7·7% of the dry body weight and accounted for 83% of the total nitrogen. The average level of amino acid nitrogen in the particulate material was 11·9 μg/1. and accounted for 54% of the total nitrogen.

The relative quantities of amino acids in Calanus remained remarkably constant throughout the year. The relative quantities of amino acids in particulate material were more variable.

The rate of respiration of Calanus measured at 8°C varied from 31 μl. O2/mg. dry body weight/day in winter (December–February) to 79 μl. O2/mg dry body weight/day in summer (April–August).

Starving winter Calanus lost 1·8% and starving summer Calanus 2·1% of their dry body weight as amino acids each day. In order to replenish its daily losses of amino acids winter Calanus must sustain a filtering rate of about 30 ml./animal/day: the corresponding value in summer is greater than 50 ml./animal/day.

The amino acid composition of Skeletonema costatum is so close to that of the particulate material in the sea, that, as far as amino acids are concerned, Calanus would gain no nutritional advantage by selecting the diatom in preference to the amino acid containing fraction of particulate material as a whole.

A description is given of Siboglinum holmei sp.nov., a shallow-water Atlantic species. It is compared with S. caulleryi, a related species from the Pacific.

The accumulation of radioactive Cs has been studied in species from the principal marine invertebrate phyla. In some species the accumulation of radioactive Cs has been compared with that of 42K and equilibrium levels of both isotopes have been related to the distribution of inactive K.

Radioactive Cs is always absorbed more slowly than 42K. Most of the inactive K is readily exchangeable with 42K so that at equilibrium inactive and active concentration factors are nearly equal. Whole animal concentration factors for radioactive Cs at equilibrium varied between 1·2 and 14 in unfed animals. These factors usually exceed those for inactive K because, although body fluid concentration factors are similar for both ions, the tissue/body fluid ratios for radioactive Cs exceed those for inactive K. Radioactive Cs penetrates rapidly into body fluids, so that uptake by the tissues is the limiting factor in accumulation. Although Cs is absorbed much more slowly than K, the eventual distribution of Cs between the tissues and body fluid of a particular species appears to bear a relationship to the distribution of K.

No evidence has been found to suggest that Cs is a necessary element which is absorbed specifically.