Worms for dissection, or for museum preservation, should be prepared by the magnesium-formalin method, of which two modifications are given in the text.

The body of Arenicola is differentiated into: (a) an achaetous ‘head’, comprising the prostomium and a small number (probably two) of subsequent segments, (b) a ‘trunk’, composed of a number, varying somewhat with the species, of chaetigerous segments, and (c) a ‘tail’, which may or may not be chaetigerous according to the species. The method of subdividing the body according to the distribution of the gills, so often met with in the literature, is misleading because it conceals the very fundamental differentiation between ‘head’ and ‘trunk’.

The main layers of the body wall are described. There are grounds for supposing that the circular muscle layer plays a greater part than the longitudinal in the maintenance of a postural fluid pressure in active worms.

The seasonal variations in the total ash, crude proteins, mannitol, laminarin and alginic acid contents are given for monthly samples of the Laminariaceae, L. cloustoni, L. digitata and L. saccharina from November 1946 to October 1948, samples of L. digitata and L. saccharina having been taken at different localities to determine the effect, if any, of the degree of exposure on the chemical composition.

The results agree favourably with those of the first 2 years examined and indicate that, with only a few exceptions, results might be reproducible in the corresponding season of any year, and it should be possible, therefore, to predict the approximate composition in subsequent years.

As before, the marked seasonal variations in chemical constitution occur in the fronds, where the bulk, if not all, of the photosynthesis occurs. The stipes undergo some variation parallel to that in the fronds, but within narrower limits, while laminarin is absent throughout the year.

A series of results is presented on the barnacle larvae population of an area of the Firth of Clyde, over a 15-day period in the spring taken by means of a modified Hardy Plankton Recorder.

The records and observations on barnacle settlement indicate that the larval population was considerably greater than usual.

The total larval population showed no great fluctuations from day to day, and on a given day the composition of the population over a wide area was often reasonably constant.

Evidence is presented that there is no great depletion of the population between Nauplius III and cyprid stages. It is suggested that the depletion previously reported may be due in part to the method of sampling or to the conditions at the time of sampling.

During the time when the evidence indicates no depletion of population there was a heavy diatom outburst, which in this instance did not appear to interfere with the larval development.

Data are given on the density of settlement.

Norman (1905) gave a short account of the distribution of the ophiuroid, Ophiopsila annulosa, having dredged it himself from Birterbuy Bay, Ireland, in 1874, and from outside Dartmouth Harbour in 1904. He also obtained specimens in 1903 from the Plymouth Laboratory; these had been dredged in 12–25 fathoms on Mewstone Ledge and Stoke Point Grounds, near Plymouth, and were recorded as not uncommon in the red sandstone, especially in old Pholadidea crypts. Mortensen (1927) expressed some doubt as to Norman's identification of the Irish specimens; he noted that the Plymouth specimens had been found in exactly the same locality and habitat as the smaller and commoner species, Ophiopsila aranea, and considered that the presence of the larger species in British waters could not be definitely settled until new records were to hand. O. annulosa was not recorded in the Plymouth Marine Fauna (Mar. Biol. Assoc, 1931) and no specimens have been found in the reference museum at the Laboratory.

Gymnammodytes semisquatnatus, the North Atlantic smooth sand-eel, has a continuous distribution from southern Norway to the southern Atlantic coast-line of Spain. Its occurrence in the Irish Sea and in the Plymouth area are new records. In the latter area it is an off-shore species, apparently concentrating in shell gravel in winter for spawning. It has a mean vertebral number of slightly over 68 (Plymouth and Scottish specimens). A small sample of the Mediterranean species, G. cicerelus, gives a mean of just over 66, while the South African species, G. capensis, which is indistinguishable from G. semisquamatus by external non-metameric characters, has a much lower mean of 58·5.

The pilchard, Clupea pilchardus Walbaum, is known to spawn in summer in the southern North Sea in the neighbourhood of the Sandettié Bank (Buchanan-Wollaston, 1911; Furnestin, 1939a, 1945) and in the eastern English Channel off Beachy Head (Furnestin, 1939a, 1945). Furnestin (1939b, 1945) concludes from these records that spawning is in all probability continuous throughout the Channel from the southern North Sea to the Celtic Sea. There appear, however, to be no previous references to pilchard spawning in the central part of the English Channel. The following records from the area are of interest therefore, and provide confirmation of Furnestin’s conclusion.

A study, now in progress, of the phosphorus cycle in the sea off Plymouth required some knowledge of the amount of plants and of several ecological groups of animals. There were no existing data except for zooplankton and the larger net-caught phytoplankton.

From information supplied by friends and colleagues, it was possible to make tentative estimates of the average biomass of other groups of animals occurring below unit area of the sea.

Sea water collected at Station E1, surface, between June 1948, and November 1949, contained suspended matter from 2·77 to 0·45 g./m.3 (or parts per million) dried and ignited. A few determinations of insoluble organic matter gave 1·77 to 1·15 parts per million dry weight at 100° C. The ignited residue contained from 55 to 17% silica, 28 to 3 of ferric oxide, 20 to under 1 of alumina and 70 (or excluding one high value 29) to 9 calcium carbonate. There was nothing in the records for temperature or salinity to suggest that the water mass had changed during the period of sampling.

The analyses reveal an unsuspectedly large amount of iron, compared with that found in solution. The ignited residue is rich in silicate, judging from the silica alumina ratio, but it is quite doubtful whether the additional supply of silicate available for diatoms is at all adequate to balance their requirements calculated on a phosphate utilization basis. It seems more probable that a considerable amount of the phosphate is available for non-siliceous phytoplankton.

Determinations of total phosphorus in water samples have shown areas in the western English Channel with water containing as little as 10 mg. P/m.3, and other areas with double, and more than double, this concentration.

The integral mean concentration of total P in the water column, 20 miles off-shore from Plymouth, has fluctuated between 10 and 16 mg. P/m.3 since June 1947.

The changes which have taken place in this integral mean concentration are attributed to different water masses, of different total phosphorus concentration, passing through the area, rather than to a seasonal change in the total phosphorus content of a water mass. No marked deposition of phosphorus-containing detritus could be found.

Changes in this integral mean were not coincident with changes in salinity. The geographical distribution of total phosphorus does not coincide with the geographical distribution of salinity.

An account is given of the bottom-fauna of Great West Bay from samples taken in 1948 with a new sampler. Comparison is made with a similar survey made by Mr E. Ford with the Petersen grab in 1923.

The deposits contain a fair proportion of mud, and the ‘EcVg’ communities denned by Ford dominate the area. Within the Bay are found fairly dense beds of Turritella communis, Lutraria sp., Callianassa subterranea and Spisula solida.

No marked changes in the fauna seem to have occurred since the earner survey. The fauna is briefly compared with that of the Plymouth area.

The volumetric and qualitative analysis of the food of Gadus minutus has been discussed. The post-larvae feed entirely on copepods, mostly Pseudocalanus elongatus. The O-group feeds on copepods, small decapods, amphipods, polychaetes and isopods. The adolescent and adult groups feed on larger decapods like Processa canaliculata, Galathea spp. and Portunus spp., fish, polychaetes and amphipods.

The age and rate of growth of G. minutus have been computed from a study of the supra-occipital crest. These age determinations have been correlated with the age determined by scales, otoliths and size-analysis. Back-calculations have been made by graphical method and by using the Lea-Dahl formula. The differences between the back-calculated lengths and actual observed lengths are negligible.

The last 20 years have seen many advances in our knowledge of the mechanisms responsible for the transmission of impulses in peripheral nerve fibres. This has come about largely through researches on the nerves of marine invertebrates. Much of the work has been done at Plymouth. The purpose of this article is to give some of the reasons why certain features of these nerves, which distinguish them from the nerves of vertebrates, should make them so desirable for experimental work.

The marine Amphipoda of the Plymouth area, as a group, were last given attention in the middle 1930's by Crawford (1936,1937). Renewed investigation after the lapse of 15 years has indicated that knowledge of species present was by no means complete, or that some changes have occurred in the interval, or both. In a recent survey of the amphipod fauna of the Isle of Man, Jones (1948) found no indication of the existence of undescribed species, nor even of known species previously unrecorded from Britain. The experience at Plymouth has been quite the reverse.

Some records are given of fishes, occasional or rare in the area, recently caught in the western part of the English Channel. The nomenclature is that used in the Plymouth Marine Fauna (Mar. Biol. Assoc., 1931) based on Duncker, Ehrenbaum, Kyle, Mohr and Schnakenbeck's list in Die Tierwelt der Nordund Ostsee (1925–29). An asterisk indicates species that do not appear in the Plymouth Marine Fauna.

The greater number of the species given in this list are new records for the Plymouth region. Recent records for some rare species have also been included.

Laminaria ochroleuca De la Pylaie was recently added to the British flora by Dr Mary Parke (1948), who found it to occur freely in the sheltered parts of Plymouth Sound. It had first come to notice in 1946 and is possibly quite a recent introduction to the country, though it may have escaped notice for some years. The species can now be recorded from two other localities: Salcombe Estuary (South Devon), and Helford River (West Cornwall).