The results of analysis of sea-water samples from the International Hydrographic Station Ei during i960 are given in graphical form and as integral mean values for the water column of 70 m. Winter maximum values for phosphate and silicate were found in January, and the spring decreases were 0-42 /xg atom P/l. and 2-23 /xg atom Si/1.

The pigments in the crowns of a number of sabellids and serpulids have been examined. The main pigments of sabellid crowns are ommochromes, but these pigments have not been found in serpulids. Both sabellids and serpulids also possess astaxanthin, and in Serpula, Protula and the sabellid Chone infundibuliformis it is to this pigment or an ester that the colour of the crown is due. The main carotenoids have been identified and the presence of a possible intermediate ketocarotenoid in amounts varying from one species to another suggests that the astaxanthin or astaxanthin ester is synthesized by the worms from carotene derived from the food. Pomatoceros has pink and blue pigments, and Galeolaria a similar grey-blue pigment which could not be identified with any known class of pigment. Neither these nor ommochromes have previously been found in annelids.

The monogenean gill parasites from Scyliorhinus canicula and S. stellaris at Plymouth have been found to be identical; their proper taxonomic designation is Hexabothrium appendiculatum (Kuhn, 1829) Nordmann, 1832. H. canicula (Cerfontaine, 1899) Price, 1942 is a synonym of H. appendiculatum.

The hexabothriid collected from Raia clavata at Plymouth has been identified as Rajonchocotyle emarginata (Olsson, 1876) Sproston, 1946, and R. clavata Bracey (in Sproston, 1946) has been shown to be synonymous with it.

The byssal apparatus appears during post-larval life when its secretion permits brief attachment during metamorphosis when the animal assumes the form which fits it for life in the adult habitat.

The byssus persists for continued temporary attachment in animals which may lose it in adult life, e.g. Mya arenaria, or in which it becomes an organ of permanent fixation, e.g. Mytilus edulis, Pododesmus macroschisma and Tridacna crocea

Comparison of the recent surveys with investigations back to 1903 confirms earlier suggestions of a general tendency towards an increase in southern forms (including south-western species) and a decrease in northern forms (including north-western species) in the western English Channel, although there has been considerable fluctuation from time to time. These and other biological changes in the area during the past 58 years are believed to be largely a result of rising temperatures and a consequent general shifting of boundaries of distribution. There appears to be no real evidence that the changes in plankton distribution are due to a change in fertility in the water or of variation in strength of inflow of oceanic water. However, these aspects cannot be separated from the changes that have taken place in populations of fish, and will be discussed further in a later paper.

In Myxicola the rapid muscular response produced by direct stimulation of the nerve cord with a single shock is usually large and obeys a simple ‘all-or-nothing’ relationship to the intensity of stimulation. A single shock of sufficient strength evokes a single giant fibre impulse which produces an extensive contraction of the longitudinal muscle.

The magnitude of the summated contraction obtained by repetitive stimulation of the nerve cord is found to depend on the number and frequency of the shocks, thus providing the animal with a mechanism by which, theoretically, it could grade its escape response.

A comparative study of the following luminous copepods was undertaken: Metridia lucens, M. longa, M. princeps, Pleuromamma robusta, P. xiphias, Heterorhabdus norvegicus, H. robustus, Heterostylites longicornis, Lucicutia grandis, Hemirhabdus grimaldii, Disseta palumboi, Euaugaptilus magnus and Centraugaptilus horridus. Flashes produced by electrical stimulation (a.c. or condenser shocks) and mechanical stimulation were recorded photoelectrically. Flashes lasted from 2 to 37 sec. Latencies of some species (Metridiidae), following electrical stimulation, were very short, 7–9 msec. Intensities ranged from 0·02 × 10–5 to 14·4 × 10–5μW/s cm2 of receptor surface at 15 cm distance (0.0045 × 10–2 to 3·24 × 10–2μW/Cm2 at 1 cm) (10–20°C). Luminous glands of Metridiidae, Lucicutiidae and Augaptilidae are autofluorescent; the location of the luminous glands in these families and in Heterorhabdidae is described. Two kinds of glandular cells (types 1 and 2) occur in the luminescent areas. The cells are large saccular structures containing granular or homogeneous material, and are distinguished by staining peculiarities. Cell types 1 and 2 open through common pores, and may be the source of luminous reactants. Some measurements of luminescence in other pelagic animals are presented, for comparison with copepods, viz. Aequorea macrodactyla, Aeginura grimaldii (Hydromedusae), Periphylla periphylla (Scyphomedusa), Meganyctiphanes norvegica and Acanthephyra pelagica (Crustacea), Myctophum punctatum (Teleostei). Our present knowledge regarding luminescence among copepods is reviewed.

Profiles of bottoms near the shore of the Isle of Man and two areas of Scotland are described, together with the vertical distribution of species of Laminariaceae. Laminaria digitata dominates over a narrow zone near lowwater springs. Unstable bottoms, providing they are sheltered enough to be habitable, support mainly L. saccharina. Stable bottoms of either boulders or solid rock support L. saccharina when sheltered (by topography or depth) from wave action and L. hyperborea when exposed. Near Port Erin, Isle of Man, the downward penetration of L. hyperborea on exposed rocks and boulders is limited by an as yet unknown factor which might possibly be associated with a slope of more than to the horizontal.

A number of damaged specimens of the scyphomedusa Poralia rufescens Vanhoffen from the north Atlantic have been examined. This has added to our knowledge of this rare medusa, of which only eleven damaged specimens had previously been recorded.

Most of the specimens were caught deeper than 1500 m.

A species of Chrysochromulina is described which habitually produces four different types of scale on one and the same cell. Scales are more opaque to electrons than in other recorded species of the genus and it has consequently been possible to trace something of their mode of production. They develop within vesicles inside the body and are subsequently deposited on the cell surface. The vesicles responsible are in a compact group beside the Golgi body and below the flagellar bases. Scale-production is at a maximum in the afternoon and greatly reduced or discontinued at night. A marked diurnal rhythm also affects other cell components, mitotic phases being abundant at 4.30 a.m. Some changes occurring in the Golgi body are described and discussed in a preliminary way.

A new species of Chrysochromulina with an unusual type of cocoon-like scaly covering has been described with the light microscope. The morphology and arrangement of the scales has been elucidated with the electron microscope. Salient features are the presence of four different types of scale (large and small plates and large and small spines) in characteristic positions in or on the case, the small plates having the normal two layers characteristic of primitive scales in this group, the other three types being specialized modifications of this. Some developmental and evolutionary consequences of the morphological observations are discussed. A preliminary observation on the thickness of micro-fibrils composing the base-plates of spined scales is given.

Low concentrations of various carcinogenic polycyclic aromatic hydrocarbons cause a considerable increase in cell production when applied to sporelings of certain marine red algae.

Whereas low concentrations of carcinogenic derivatives of benzanthracene stimulate cell production, similar concentrations of structurally related non-carcinogens inhibit it.

The applicability of the method as a rapid screening test for carcinogens is discussed.

An accessory organ of the circulatory system has been found in Sepia officinalis and Loligo forbesi, situated on the inner surface of the mantle around the posterior pallial vessels. It is spheroidal in shape and consists chiefly of muscle fibres forming bundles anastomosing with one another, most of them taking a general circular course round the artery and the vein. In Sepia the muscle bundles are more loosely arranged, being imbedded in connective tissue of soft consistency; they are not continuous either with the musculature of the vessels or with that of the mantle, and show certain structural differences from them. The nerves approaching this organ from various directions carry elements of two systems: (a) fibres given off by the branches innervating the neighbouring mantle muscles; (b) elements of the vasomotor system; these are 3 trunks consisting of fibres of small calibre and containing groups or rows of ganglion cells. One of these trunks associates with one of the main mantle nerves, another runs through the retractor muscle of the branchia. Within the accessory organ they intermingle with the motor fibres, but the nerve bundles passing to the posterior pallial vessels consist of fibres of the vasomotor system only; it is possible that the muscles of the accessory organ are supplied, in addition to their motor innervation, with fibres of the vasomotor system.

Gastrocotyle trachuri and Pseudaxine trachuri infect young Trachurus trachurus at Plymouth as soon as the 3- or 4-month-old adolescent fishes descend to the sea bottom in October. The parasites normally mature in 3 or 4 months, but, exceptionally, in about 1 month, and the life-span is normally no longer than 1 year. Trachurus specimens at the beginning of their second year pick up a largely new infection of parasites.

G. trachuri and P. trachuri are much less frequent on 2- and 3-year-old specimens of Trachurus and probably occur only very rarely on still older fishes, the limiting factor being not an age-immunity but a post-spawning migration of the host from the concentration of free-living infective stages of the parasites in coastal waters.

The parasites have adapted themselves to a seasonal change in the feeding habits of Trachurus by ceasing to produce larvae in anticipation of the summer disappearance of scad from the sea bottom in pursuit of pelagic food-organisms.

Spirorbis corallinae sp.nov. is very similar to S. borealis but can be distinguished by its orange colour, small size, bifid opercular talon and particularly by the fact that the larvae choose to settle on Corallina officinalis rather than on Fucus serratus.

Other species dealt with, in a key to identification and notes on distribution, are S. granulatus, S. malardi, S. pagenstecheri, S. rupestris, S. spirillum and S. tridentatus.

The functional morphology of the veliger, pediveliger, and early post-larva of Venus striatula is described. Settlement takes place at a length of 220- 240 /u, and is marked by the rapid loss of the velum, functioning of the byssus gland, and commencement of secretion of the post-larval shell (dissoconch). With the exception of the loss of the velum, the changes which occur at metamorphosis take place relatively slowly. The significance to phylogeny of the mode of development of certain organs in the post-larva is discussed. It is concluded that the form of many of the organs in development, especially of those organs concerned in producing a respiratory and feeding current, are juvenile adaptations, resulting in the early functional re-adjustment of the free-swimming larval habit to a bottom-living habit, but having little or no phylogenetic significance.

An area in the English Channel of about 30 x 45 miles centred on a position about 25 miles south of Plymouth was surveyed twice in 1959 and six times in i960. Temperature and salinity were measured at 0, 10 and 50 m, and phosphate and silicate concentrations at 10 and 50 m.

Lower temperatures were usually found near the coast, though the converse was observed in October i960.

Isotherms generally ran east-west in winter and north-south in summer.

Salinity was usually lower near the coast, but not in the summer.

Density contours generally resembled those of temperature, and suggested an eastward water movement in winter. In summer they suggested an offshore movement at the surface and an onshore movement of the deeper water.

In winter the distribution of phosphate and silicate resembled that of salinity, high values of nutrients corresponding to low salinities.

In summer the depth of thermocline was greater to the west

The properties of the water were so variable from place to place, and changes in them so rapid, that it is difficult to accept results from station Ei, or any other single station in the area, as typical of the whole.