Effects of water of reduced salinity on the vertical migration of the zooplankton of Southampton Water were investigated in the laboratory using the adults of six copepod species (Acartia tonsa, A. bifilosa, A. discaudata, A. clausi, Centropages hamatus, Temora longicornis) and the larvae of one decapod species (Porcellana longicornis). Additional observations were made on Centropages typicus adults taken off Plymouth.

Salinity discontinuity layers had a marked effect on the vertical migration of zooplankton. A single discontinuity layer formed by placing less dense diluted sea water over full strength sea water acted as a barrier to animals attempting to swim toward the surface of an experimental water column and no individuals were able to enter the zone of reduced salinity when an extreme dilution was used. Comparison of the behaviour of various species and of different sexes or developmental stages of a particular species suggests that vertical distribution was partly dependent on the salinity tolerances of individuals. Upward migration was also restricted by a vertical series of discontinuity layers.

The swimming activity of copepods was depressed in homogeneous water columns of reduced salinity. Activity depended both on the degree of dilution and on the period of immersion. There were indications that behaviour varied according to the salinity tolerances of the different species.

A method is described for obtaining the venom from the dorsal fin of the lesser weever without harming the fish. It is suggested that the amount of venom normally injected into the wound by the weever when it stings is O-5-O-2 mg dry weight of venom. Some 60% of the dry weight of the venom appears to consist of toxic muco-substances, which have a neurotoxic effect, but are without toxic effect on the blood. In extracts this fraction may be separated into two albumins and an amino polysaccharide, though in the native venom these are probably associated into a single complex mucosubstance. When injected subcutaneously this fraction of the venom produces no local pain. The venom also contains about 1-20 jug/mg (dry-weight basis) of 5-hydroxytryptamine which appears to be the origin of the pain of the sting, together with some undetermined histamine releaser (not an indole) of low molecular weight. It is suggested that the chief role of the 5-hydroxytryptamine in the venom is to produce pain around the area of the inflicted wound.

The range of temperatures over which the cirri were active and the frequency of beating at different temperatures were measured in four species of barnacles collected on the southern and south-western coasts of France. The extremes of high temperature at which the animal remained irritable or could survive were assessed in these species and in a further group of species from Trinidad, West Indies.

The results are discussed in comparison with previous evidence for species of more northern distribution, and related to the geographical range of the species and the ecological niche occupied. For example, the brackish water species, Balanus eburneus and B. improvisus, have similar patterns of cirral activity, but the greater tolerance of high temperatures shown by the former is obviously connected with its more tropical distribution. Differences in temperature tolerances of varieties of JB. amphitrite from Europe and Trinidad, possibly related to differences in the tide levels at which they live, tend to reinforce their separation on morphological grounds. More pronounced differences between Chthamalus depressus and C. stellatus confirm the separation of these two species which were formerly regarded as varieties. The relatively lower rate of beating of C. depressus which is not found north of the Mediterranean and its greater tolerance of high temperatures compared with C. stellatus, may be related to its more southern distribution and its ability to live at very high levels on the shore. These two species and C. fragilis from Trinidad all show greater tolerance of high temperatures than the species of Balanus and Tetraclita, which are found at lower levels on the shore

It is concluded that in the North Atlantic area there may be only two main distributional groups of species of acorn barnacles, Arctic and Tropical, overlapping in the Temperate regions, with few or no intermediate forms, and that there is as yet no evidence for the existence of physiological races in these species.

The external and internal structure of the spines of Squalus acanthias are described. Internally the spines consist of a series of dentine cones laid down one within the other. This series is reflected in the external structure by bands of pigment associated with ridges of enamel. The latter are proved to be annual.

The use of the spines for age determination is discussed and the growth parameters and growth curves calculated. The results obtained differ from those of previous authors, whose work is critically discussed.

The accumulation of 137Cs from sea water has been examined in relation to potassium metabolism in the lobster Homarus vulgaris and in the prawn Palaemon serratus. In unfed animals 137Cs is taken up and lost far more slowly than 42K. Although all the inactive K in the animals can be exchanged with 42K, higher whole-animal concentration factors are reached for 137Cs (about eight for lobsters and twenty-five for prawns). This is because both species have higher plasma/medium ratios for 137Cs than K at equilibrium despite the selective excretion of 137Cs. Also, except for the hepatopancreas in lobsters and fed prawns, all soft tissues can probably attain higher tissue/plasma ratios for 137Cs than inactive K.

Uptake of both isotopes has also been studied in the freshwater crayfish Austropotamobius pallipes pallipes. In crayfish in o-i % sea water 137Cs is not concentrated to the same extent as K by whole animals (50-200 for 137Cs against about 4500 for K). Although the situation between plasma and tissues resembles that in the marine animals, 137Cs cannot be accumulated in the plasma to the same degree as K. Crayfish selectively excrete 137Cs in the urine relative to K at a lower concentration than in the plasma.

In the accumulation of 137Cs by all species, muscle is the principal limiting factor in uptake and loss, but with 42K the body surface becomes more limiting.

Experiments on the absorption of 137Cs from food in prawns and freshwater crayfish have been carried out. In prawns in a constant environment, feeding is probably less important than uptake over the body surface while in crayfish feeding is probably much more important.

Pelagic plaice larvae in the southern North Sea normally feed exclusively on the appendicularian Oikopleura dioica, and the size of prey eaten can be estimated from the Oikopleura faecal pellets found in the larval gut

Predator-prey size measurements show that smaller plaice larvae are restricted to smaller prey, and that, as larval growth proceeds, so their feeding versatility increases, to include all sizes of Oikopleura at a late pelagic stage of development. Competition for food will therefore be keenest in the early larval stages, when prey-size restriction prevails. This accords with Hjort's hypothesis regarding brood strengths.

As growth proceeds, so plaice larvae begin to discriminate for prey size. At the close of the pelagic phase, the degree of size selection is roughly equal to that of a 6o-mesh to i in. plankton net.

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.

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.

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 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.

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.

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.