The superficial red muscle fibres of gnathostome fishes run more or less longitudinally, but the deeper muscle fibres are arranged in complex three-dimensional patterns in which some of them make angles of 30° or more with the long axis of the fish. There are two basic patterns, of which one is found in all the myomeres of selachians, primitive bony fishes, Anguilla and Salmo. In the other teleosts which were examined this pattern is restricted to the last few myomeres, and a quite different pattern is found more anteriorly.

In a fish with muscle fibres running longitudinally the lateral fibres would be able to contract far more than those near the vertebral column. However, from mathematical analyses included in this paper it appears that both the patterns which have been found should result in all the white fibres in a myomere contracting to a fairly similar extent when the fish bends. This seems likely to be advantageous because a muscle fibre of given intrinsic speed produces maximum power output at one particular rate of contraction.

A given rate of contraction of the muscle fibres results in faster bending if the fibres are arranged in the typical teleost pattern than if they are arranged in the selachian pattern.

The selachian pattern is probably retained in the caudal peduncles of teleosts because the faster bending is obtained only at the expense of weaker bending moments. The caudal peduncle is slender and would be less able to transmit large forces to the caudal fin if the teleost pattern of muscle fibres were continued to its posterior end.

Experiments were carried out to assess the importance of desiccation during tidal exposure upon the vertical distribution of the intertidal limpets Patella aspera and P. vulgat vulgata. The rate at which water is lost during desiccation varies inversely with body size.

The numbers of young fish, excluding clupeids, taken in a 2 m ring trawl in the plankton off Plymouth were as high in the year 1966 as they were during the 1920s and early 1930s. There is thus evidence that the period of decreased abundance which began after 1934 and has apparently persisted since then may have ended. The year 1966 was a very early year for spring spawners and this can be correlated with the high water temperatures prevailing in the early months of that year.

Results of quantitative surveys of the polychaete fauna of certain fine deposits within Plymouth Sound, comprising a total of forty-eight species, are presented. The juvenile stages of certain species are described and sixteen species that have not been found previously in the area are recorded.

The settlement behaviour of the larvae of Ostrea edulis has been examined in the laboratory. Preliminary experiments indicated that high light intensities (1250 lux) and food-cell concentrations (100,000 cells/larva) stimulated settlement, but varying the temperatures within the range 19–23 °C had little effect.

The muscle fibres of the radial muscles of the unpaired fins of dogfish can be divided into two populations—an outer group of red muscle fibres which are smaller and fewer than the inner white muscle fibres and which differ in structure, number of nuclei and pattern of innervation. Two types of potential were detected in the two muscle systems when recordings were made with implanted electrodes during movements of the fins. The red muscle fibres were associated with small, slow junctional potentials which changed in amplitude when the activity of the system was altered.

The general biology of Leptomysis gracilis (G. O. Sars) and L. lingvura (G. O. Sars) is described. There are three main generations of L. gracilis, spring, summer and autumn ones, produced during the year, although breeding is continuous in the population between the most productive periods. Females carry as many as sixty young in the spring and summer but usually less than twenty in the winter months.

Parasites occurred on Erythrops serrata (G. O. Sars) and E. elegans (G. O. Sars) caught in the Clyde sea area and were identified tentatively as species of Thalassomyces, belonging to the Ellobiopsidae (Mauchline, 1968). Wim Vader of the Biological Station, Espegrend, Norway, however, on seeing the drawing of the parasite published by me pointed out that it was more probably a species of choniostomatid copepod. The parasites have now been re-examined and compared with Hansen's (1897) descriptions of these copepods.

The primary productivity of an area of inshore sea in the South Orkney Islands was measured using in situ techniques in two consecutive seasons. Liberation of extracellular products of photosynthesis occurred, accounting for about 1 % of the total carbon fixed at the depth of maximum photosynthesis but rising to 38 % or more when photosynthesis was inhibited at high light intensities.

Introduction

Monthly samples of Argentina sphyraena L. taken in the Clyde Sea Area over 2 years were used to describe age, growth, length-weight relationship, annual cycle in condition, and mortality. Results indicate that one transparent ring is laid down in the otoliths each year between November and May, providing a means of ageing this species.

The biology of the marine leech Oceanobdella blennii, ectoparasitic on the littoral fish Blennius pholis, was studied on the coast of North Wales from 1964 to 1966. Leeches first appeared on the fish in large numbers in December, but were less common in January. During February and March they became more abundant on individual fish and among the host population as a whole, but in April and May the leeches began to disappear and none was ever found from June to November.

A study has been made of the relationship of Phaeodactylum tricornutum (Bohlin) to iron, manganese and zinc. Evidence is presented showing that, in batch culture, the three elements behave differently as regards their uptake into the cells, the amounts present in the cells and their distribution between cells during the growth of the culture. The implications of these differences are considered.

A similar inhibitor has been found in red mullet {Mullus surmuletus L.), megrim (Lepidorhombus whiff-iagonis Walbaum) and greater forkbeard (Urophycis blennoides Briinnich). The inhibitor is of a seasonal nature in these fish also and may be linked with the spawning cycle.

The responses to light and temperature variations of the gametophytes and early sporophytes of Laminaria hyperborean were compared in culture with those of its main competitors in Britain, namely L. digitata, L. saccharina and Saccorhiza polyschides. Some undeveloped gametophytes of all species are able to survive in the dark for at least 80 days.

The effects of salinity, light intensity, temperature and pH on the amounts of nitrogen fixed and liberated extracellularly by the marine blue-green alga Calothrix scopulorum (Weber et Mohr) Ag. ex Bornet et Flahault have been investigated.

This is preliminary to a series of papers resulting from SOND 1965 Cruise aboard R.R.S. ‘Discovery’. The cruise was designed as an ecological study of sonic scattering layers at a certain season in a restricted volume of ocean in the region of the Canary Islands. These papers will appear periodically in this journal.

The ostracods have been analysed from a day and night series of horizontal tows taken near the Island of Fuerteventura (Canaries). Thirty-five species were identified. Nineteen species were sampled in large enough numbers to describe their depthe distributions and the ranges of their vertical migrations. Seven species were too small to have been adequately sampled by the methods used, and the remaining nine species were too rare to draw any firm conclusions as to their depth ranges.