A method is described for investigating the reactions and spontaneous activity of two species of ascidian, Phallusia mammillata and Ascidiella aspersa, which does not disturb the animals unduly. The method can be used for obtaining graphic records of the so-called ‘reflexes’ of ascidians.

If due attention is paid to certain factors which affect the state ofthe animals, they can be made to respond to electrical stimuli applied to the outside of the test in a way which can be observed repeatedly in the same animal, in other animals of the same species and in at least two genera of ascidian.

Electrical stimuli applied to the test affect the excitable system of the whole animal in an all-or-nothing manner.

Response to graded electrical stimulation reveals a facilitation mechanism which gives enormous enhancement to the size and speed of response to the second of a close pair of effective stimuli. It is suggested that this mechanism is responsible for the production of the rapid squirt of the large sedentary ascidians.

A possible cause of the very rapid fatigue of ascidians to all kinds of stimulation is fatigue of the facilitation mechanism following a period of stimulation.

A parallel is drawn between the responses of Metridium and the responses of Phallusia and Ascidiella. The responses have some common features and the response mechanism appears to serve a similar purpose in the life of the animals.

In the course of some studies on the kinetics of growth and the biochemical activities of a marine diatom it became desirable to obtain bacteria-free cultures. The classical method of obtaining such pure algal cultures involves either repeatedly washing single cells in sterile medium or obtaining discrete bacteria-free algal colonies by growth on a solid medium. Both these methods have been widely applied to fresh-water species by Pringsheim (1946) and others, whilst Chu (1946) has used both methods with the marine diatom Nitzschia closterium (Ehrenberg) Wm. Smith forma minutissima.

Marine algae supply good examples of the difference between ‘ecological’ and ‘non-environmental constitutional’ resistance of the protoplasm of their cells to variations in the environment. The resistance to ecological factors such as diluted or concentrated sea water, to desiccation, or to light exposure is very similar among algae occupying the same habitat. On the basis of the degree of resistance shown, three ecological groups can be distinguished: (1) algae from the intertidal zone; (2) algae from the low-water level and tide-pools; and (3) sublittoral algae.

On the other hand, there is no similarity in the resistance to chemical substances (H3BO3, ZnSO4, MnSO4, VOSO4) of algae within a given ecological group. It is characteristic for a given species.

In previous papers (1932, 1933) the author showed that sea water taken from the English Channel contained about 10 mg./m.3 of copper, and obtained agreement between electro-deposition with subsequent colorimetric analysis and colorimetric analysis carried out on sea water concentrated to one-fifth of its volume. For extraction of the copper complex, carbon tetrachloride was found to be the most convenient solvent. The changes throughout the year have, however, only recently been determined. It is of interest to see that water from Station E1, surface, taken 23 March 1931, gave 10 mg./m.3 by direct colorimetry and 9·7 with electro-deposition, whereas the extraction method curves for 1948 and 1949, read off for the same date, showed respectively 9·4 and 11·4 mg./m.3.

A summary of the trematode parasites which have been recorded from the cockle is given.

A furcocercous, Gymnophallus larva, Cercaria fulbrighti n.sp., from the marine bivalve Cardium edule L., is described from Plymouth, England. The tail of this larva may degenerate completely while the cercaria is still within the sporocyst.

Simultaneous development of more than one species of cercaria has been recorded in four out of 420 specimens of C. edule L. Two double and two triple infections were found.

Available evidence suggests a phylogenetic relationship between the Gymnophallus group and certain of the Furcocercous cercariae.

Many experiments have been made in the laboratory by different workers to study the swimming behaviour of plankton animals in relation to light and other factors. At the present time the special apparatus described by Hardy & Bainbridge (1951) is being used for a study of vertical migration, and other experimental work on the inter-relationships of zooplankton and phyto-plankton (Bainbridge, 1949) is also in progress. Both this type of work and current theories (see Cushing, 1951) on the migrations of zooplankton make it of some consequence to learn the actual nature of the movements of these animals in the sea itself; and it is of special importance to compare their swimming behaviour in the different types of apparatus with their behaviour in the sea.

Chlorophyll from the phytoplankton at station Ei was examined from September 1951 till August 1952, from o to 50 m. The minimum was in June, i-8 mg./m.3, and the maximum 342 in March, both surface samples. The maximum 50 m. sample contained 18-4 mg./m.3 in April. The winter minima were 4-6 and 43, surface and bottom, in November. Converted to water column (70 m.) values, over iog./m.2 is obtained for the wet weight of phytoplankton for September and March, the April maximum and the June minimum being 132 and 015 g./m.2. A comparison with the production obtained from phosphate analyses suggests that the phytoplankton crop each month is rapidly devoured.

Exact proportionality was found between concentration and absorption in a chlorophyll band up to 40 mg./l. and a moderate error up to 80 mg./l. The spectral absorption curves have been given for pure cultures of phytoplankton and for cells filtered out of sea water. The chlorophyll in such extracts, made with 80% acetone, is stable when kept in total darkness.

The collodion disks containing suspended clay arid the algal cells may show a surprising variation in their colour intensity, from dark grey to a very faint tint, even though obtained from sea water about 20 miles from land and over 70 m. in depth. The surface may be far darker than 5, 10 or 15 m. samples.

The botanical composition of the water was studied by allowing the algae to multiply in diffuse light after enriching the water chemically. Eight species of Chlorophyceae, and one species each of the Chrysophyceae and Dinophyceae were recorded. Of the Cryptophyceae one winter sample from 50 m. gave a nearly pure growth of Hemiselmis rufescens Parke. The diatoms Melostra borreri, Nitzschia closterium and Navicula sp. occurred commonly.

Luminescence inChaetopterus is an extracellular phenomenon and is due to the secretion of photogenic material by certain glandular cells in definitely circumscribed regions of the body. These gland cells are eosinophihc elements scattered singly or massed together in dense aggiegations in certain regions. They are particularly abundant in the epithelium covering the distal surface of posterior notopodia, and in two glandular areas on the dorsal surface of the aliform notopodia. These two regions also display the brightest luminescence (Nicol, 1952 a).

International hydrographic station England no. 1 (EI) has been visited regularly for many years, and since 1921 the periods have been (nominally) once a month, or more frequently. Much work has been done on the plankton and chemical changes in the water, but no biological use has been made of the temperature-depth observations, which are primarily of hydrographic importance. The aim of this paper is to render the sea-temperature observations over this long period readily available and to place beside them observations on air temperature, sunshine and light. Such comparisons may be expected to give information upon the causes of variations in temperature, but the adequate investigation of this very difficult problem is outside the scope of this note. The subject is worthy of fuller treatment on the lines suggested by Harvey (1925), based on data for the years 1921 to 1924, and has been considered on broad lines by Sverdrup, Johnson and Fleming (1942).

A trade waterproofing of sisal rope had still some effect after 3 days in sea water, the untreated being four-fifths saturated in 1 hr.

Treating manila, sisal and coir rope with Cuprinol or tar increases the wet weight at the most only slightly as less water is taken up than without preservative.

Water equilibrium is not attained till long after the B.S.I, specification test period for waterproofing sisal rope, but some effect of waterproofing may be distinguished up to perhaps 3 days.

On cotton netting copper naphthenate preservatives were most durable in a clean sea-water basin, but Dr Olie's method with cutch and ammoniacal copper sulphate ran them close and is cheaper. The best lasted 9 months as against untreated 5½ months.

On trawl twines the British Columbia grade of Cuprinol, a proprietary mixture containing copper naphthenate, was the best of those tried, and the twines lasted 16 months as against almost 9 for untreated manila.

On thin sisal rope six copper preparations are still under test.

In the course of a study of the British Nuculidae the specific characters of a large number of specimens of N. turgida and N. moorei were re-examined. It was found that no distinction could be made between the two.

Examination of variation in shell colour showed that it was not possible to differentiate into two distinct types. There was a continuous graded seiies from a dark purple-grey in which the basic yellow colour was almost completely masked, through a series with decreasing numbers of purple-grey radiations, to shells in which the markings could not be differentiated as rays, and finally to shells without purple coloration. The purple-grey colour is not necessarily laid down continuously, and it does not develop until the end of the second year. As the shells get older an increasing percentage of them become coloured.

Although the two types of faecal pellets described by Moore were found they could not be associated with the radiate and non-radiate shell types. The five grooved faeces that he claimed were typical of the radiate variety, were found in only three of the fifty-six specimens examined. Only one of them was from a definitely radiate shell.

Shell measurements and growth rates were studied, and no feature was found on which two forms could be separated. Samples show that reproduction takes place at the same time in the rayed and unrayed shells.

As the name N. nitida Sowerby is preoccupied it is suggested that the name N. turgida Marshall should now be used with N. moorei a synonym of it.

In one experiment sea water from the Firth of Clyde yielded better cultures of Echinus esculentus larvae than did sea waters from two positions in the English Channel.

From the Clyde water materials of unknown composition were extracted, using active carbon and acetone. The addition of these materials to both Clyde and Channel waters resulted in the death of the Echinus eggs during early cleavage. A similar extraction from Channel water had the same effect. The Clyde and Channel waters from which these materials had been extracted gave poor abnormal cultures, especially the Channel water in which most larvae died early. A few, however, survived, and later on some of these grew into almost normal plutei.

The present study forms part of a more extensive one on the ecological factors which govern the distribution of the microfauna inhabiting seaweeds on rocky sea-coasts. This part of marine ecology is lagging far behind other branches. I wish to stress two points in particular: fasirst, that our understanding of the composition of the littoral (intertidal) fauna would increase very much if this fauna can be linked with the true infralittoral fauna, and, secondly, problems involving the synecological aspects of marine biology cannot be approached before more is known about the autecology of the animals composing the cryptofauna (i.e. those living in the shelter of algae) and the causal factors determining their occurrence and distribution within a given area under stated conditions. On this point the work of T. A. Stephenson is especially relevant: as a result of his extensive investigations on the composition of the intertidal flora and macrofauna he has come to stress the importance of autecological rather than of biocenological work on the shore (Stephenson et al. 1942; Stephenson, T. A. & A., 1949). Moreover, he has clarified the intertidal terminology and introduced the most useful terms “supra-” and ‘infralittoral fringe”. Since his terminology appears to be the best suited to meet the needs of ecologists, I hope it will be generally applied in future. Most work on littoral ecology has been limited to macro-organisms, valuable data on the ecology of microfaunas of seaweeds have been supplied by Colman (1940), Kitching, Macan & Gilson (1934), and Dahl (1948).

The black body-wall pigment of Holothuria forskali shows the characteristics of melanin.

From histological evidence it appears that the pigment is formed in association with the amoebocytes of the coelomic fluid, which eliminate the pigment in the body wall.

The amoebocytes contain a phenolase system, distinct from the cytochromecytochrome oxidase system, with the properties of tyrosinase.

The relation of these findings to those of a preceding and more complete investigation into melanogenesis in Diadema is discussed.

Notable catches of boar fish (Capros aper) were taken near the Eddystone on 30 October and in early November 1951. From what is known of the distribution of boar fish and from the hypothesis on the genesis of “submarine eagres” in canyons on the continental slope, a further hypothesis has been derived to explain this occurrence. It is suggested that strong west to south-westerly winds on 24 September created conditions to produce a submarine eagre the following day, and that this swept a shoal of boar fish from the yellow-coral encrusted walls of a submarine canyon in the southern edge of the Celtic Sea on to the continental shelf. Thence during quiet weather the shoal was carried by currents to the neighbourhood of the Eddystone at about 6 miles a day. Further deductions which lead to means of checking the present hypotheses have been drawn.

Our lack of knowledge of nanoplankton organisms is due largely, no doubt, to the necessity for examining them alive and the comparative difficulty of observing them, and also to their being, apparently, of no more than indirect importance in the ecology of fishes, except when their occasional presence in great abundance has been accompanied by unfavourable hydrographical changes. An adequate survey of life in the sea is bound to take them into account. Since they are frequently abundant, at least in inshore waters, and propagate rapidly, they probably form an important constituent of the food of adult filter-feeding invertebrates. They are likely to be of still greater importance as the essential food of many planktonic larvae, particularly in the early stages. Oyster larvae (Ostrea edulis L.) can ingest nothing larger than about 10 μ and appear to rely for food on minute flagellates (Cole, 1936,1939; Bruce, Knight & Parke, 1940). The food of other marine larvae has not been closely investigated.

The aquarium or tank room, to which visitors are admitted on payment of a small charge, was not designed primarily for public display, but was intended principally to facilitate scientific observations on the habits and life histories of marine animals. This original purpose it has never lost, but of recent years it has increasingly catered also for the steadily growing number of people interested in natural history, and for numerous classes of school-children brought by their teachers. Since the aquarium was re-opened in November 1946 attendances have shown a big increase over comparable pre-war figures.

The previous work on spontaneous activity in ascidians is briefly reviewed: there is clear evidence for the existence of spontaneous contractions of the siphons of certain monascidians but no function has been ascribed to this activity. Phallnsia mammillata exhibits spontaneous contractions of its siphons at intervals of 6-9 min. over long periods in Plymouth tank sea water. The siphon contractions are synchronous. The frequency of the contractions may shift fairly quickly under constant conditions to a higher or lower rate which is usually twice or one half the normal rate.

A method of recording the volume of water propelled by spontaneous activity is described. The method also records the ciliary through-current at the same time as the squirts.

The frequency of the squirting is increased during a period of partial or complete starvation. It is reduced again by adding food cultures to the water.

The physiological mechanisms involved in the spontaneous activity are investigated and comparisons are made with the spontaneous activity exhibited by Metridium senile and Arenicola marina. It is finally suggested that the spontaneous squirting of certain ascidians is an integral part of their feeding mechanism.

In the pericardial cavity of the decapod Crustacea the nerve fibres end in characteristic neuropile-like networks which surround bundles of thicker fibres or spread over the pericardium wall and the heart ligaments. It is proposed to designate the whole system of these elements as 'pericardial organs'.

The arrangement of the elements constituting the pericardial organs varies in different groups of the Decapoda. In the Brachyura the bundles of fibres surrounded by neuropiles form conspicuous trunks linked with each other; the main parts of these trunks are situated at the openings of the branchiocardiac veins into the pericardial cavity. In Eupagurus bernhardus two main trunks flank the heart giving off branches which spread in various directions and form at some places plexuses on the pericardium wall. In Leander serratus the pericardial organs are represented by several trunks running near the lateral wall of the pericardium in the dorsal direction and uniting by archshaped branches. In Homarus vulgaris there are four comparatively much shorter trunks situated at the lateral wall of the pericardial cavity, but plexuses of neuropile-like nerve fibres spread over large areas.

The trunks of the pericardial organs are suspended in the pericardial cavity in such a position that they may be bathed on all sides by the blood passing from the gills. The plexuses extending over the membranes are situated in places also exposed to the blood stream. There is evidence indicating that the pericardial organs produce substances influencing the heart-rhythm. It is assumed that these substances are liberated into the blood by a process of neurosecretion occurring at the terminations of the nerves.