An improved underwater photographic apparatus has been used to take further series of photographs of the sea bottom near Plymouth. The photographs in the present series are each ¼ m.2 in area instead of 1 m.2, and at this scale definition is much better.

Photographs of the bottom in the Rame Mud area showed ripple marks but no living epifaunal animals. In an area south of the Rame Mud, on a muddy sand and gravel bottom and in a similar area 6 miles south of Looe, dense populations of the brittle-star, Ophiothrix fragilis were photographed. In the area south of Looe this type of population (density more than 100 individuals per m.2) ha s been photographed on three different occasions in 1950–1. In a similar but still denser Ophiothrix population found ¾ mile north-west of Eddystone, there were about 340 individuals per m.2, and this aggregation was apparently of long standing, since exceptionally large dredge hauls of Ophiothrix were taken there in the last decade of the nineteenth century. It is suggested that the food supply for these populations, in the form of suspended material, is brought to them largely by the tidal streams and that the crowded beds are in localities where this is likely to happen.

Two experiments on the reaction to ultra-violet light of certain sound scatterers in the area are described.

The source was a 125 W. ultra-violet lamp.

The scatterers were detected using a Kelvin and Hughes recording echo-sounder, type 22.

The traces on both occasions were of the confused type caused by a number of different organisms, apparently lying between 20 and 60 m. and 8 and 30 m. respectively.

The responses of the different organisms to the ultra-violet light as shown by the components of the traces are described and their speeds of reaction calculated.

The types of organisms causing the traces are suggested.

Planktonic, benthic and littoral Crustacea were collected from localities around the British coast, from Norwegian and Faeroese waters and from the Antarctic, and their content of preformed vitamin A and carotenoid pigments was measured.

Methods are described for the preservation of specimens, the extraction and separation of vitamin A and carotenoids and the measurement of vitamin A by chemical, physical and biological tests, and of carotenoids by physical tests.

Free-swimming euphausiids were found to contain, in addition to large quantities of astaxanthin, high concentrations of preformed vitamin A, but no β-carotene.

Pandalus bonnieri is a dioecious species and no protandrous hermaphrodites have been seen.

The breeding season and incubation period for P. bonnieri are described.

The number of eggs laid increases with the size of the female. At 16 mm. carapace length the number of eggs is c. 1000 and at 24 mm. carapace length the number of eggs is c. 4000. The number for a single mm. size group varies roughly by ±10%.

Both male and female P. bonnieri become sexually mature at about 18 months, and in the Clyde seldom live beyond 3 years of age.

The colour of the eggs in P. bonnieri is sage green, in P. borealis blue green, in P. montagui light emerald green and in P. propinquus fawn.

Juvenile P. bonnieri can be separated into males and females by the shape of the pleopods within 4–6 months of hatching.

Records of nearly 2000 dogfish collected from the Ilfracombe region suggest that the spawning season of this fish starts in November and continues at least until July. This area probably represents a spawning ground into which the females migrate during the spawning season; the males follow them much later in April and May.

Figures are given to show the time taken at different temperatures for the embryo to develop to a series of definite morphological stages; these suggest that the temperature characteristic of the development (µ = 20,000) is substantially the same as for several teleost species.

In the dorsal wall of the abdomen in the Paguridae muscle receptor organs have been found similar to those in the Macrura. In each of the first to fifth abdominal segments there are two receptor units on each side. A receptor unit consists of a long thread-like muscle, and a nerve cell connected with this muscle and sending its axon towards the central nervous system. The muscles of each pair run close together in the layer of the dorsal (extensor) muscles, but are independent from the latter following a more or less different course.

The nerve cells in each pair of muscle receptor organs are of two types. One of them has several very long distal processes expanding over one of the muscles. The other cell has one stout distal process giving off numerous but very short branches forming with their subdivisions a dense tuft of fibres terminating in the second muscle. The axons of the cells associate with one of the branches of motor nerves supplying the dorsal muscles and pass along these branches into the main nerve trunks of the respective segments.

Each receptor organ is supplied by several nerve fibres coming from the central nervous system.

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.

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.

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.

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).

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.

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.