The number and size of colonies found in bacterial counts of sea water collected from the Menai Straits varies with the concentration of peptone in the medium. The optimum concentration of peptone was found to be 0.3%. Neither yeast extract, beef extract or added iron increased the count when added to media made from Menai Straits water. The effect of various temperatures on the count, and the relative merits of pour plates and surface growth techniques were examined. Vigorous shaking, or passage through a Sharpies centrifuge, was found to increase the count.

As part of the programme of study of the geology of the western approaches initiated at Bristol by Prof. W. F. Whittard (Whittard, 1962) information has been accumulated concerning the distribution and nature of the metamorphic rocks exposed in a series of inliers between Start Point in the east and Dodman Point in the west.

Early dredgings in this area were described by Worth (1908). Six core samples and two dredgings of metamorphic rocks are listed by Hill & King (1953). Mica schist in situ is recorded by Holme (1953). Various cruises in R.V. ‘Sarsia’ from 1957 onwards have yielded seventeen cores and further dredged samples. Additional material, collected from the exposed parts of the Eddystone reefs or obtained by diving at critical localities, has become available through the kindness of members of the staff of the Marine Biological Laboratory at Plymouth.

Sixteen cores and eight dredged samples serve to demarcate an area of schistose rocks, extending some 24 miles from east to west and 7 miles in maximum width from north to south, off the southernmost part of Devon (Fig. 1). These rocks, with an exception to be noted, compare closely with those exposed on land, between Bolt Tail and Start Point, south of a well defined east-west boundary (Ussher, 1904; Tilley, 1923). There are examples of quartz-muscovite-chlorite schists precisely like the Start Mica-schists and Bolt Mica-schists described by Tilley. Albite porphyroblasts, in a rock dredged near East Rutts (Fig. I, 1262) which is transitional to Tilley's ‘schists of composite origin’, show well the contorted swarms of carbonaceous inclusions which he describes (1923, p. 180).

A survey at Hamble Spit showed that C. tentaculata was less abundant near high water mark than farther down the shore. The influence of various environmental factors on the worms' distribution was investigated, and it was concluded that temperature, salinity, oxygen content, and water content were of minor importance. Both the particle size of the mud and its carbon content showed some correlation with the abundance of the worm. However, periodic strong wave action seemed to have the most influence on the distribution of the worm over the mudflat.

Nerves known to supply the anterior part of the vena cava in Cephalopoda have been found to belong to a special system for which the term ‘neurosecretory system of the vena cava’ (NSV system for short) is proposed. In Eledone cirrosa this system consists of neurons whose cell bodies are aggregated: (a) in the visceral lobe in a layer termed the NSV layer; (b) in the ganglionic trunks continuous with this layer and associated with nerves arising from the visceral lobe—there is on each side a ‘lateral NSV trunk’ accompanying the nervus infundibuli posterior, and a ‘medial NSV trunk’ accompanying the nervus visceralis. Each of these trunks in its further course separates from its nerve and runs far in the caudal direction diminishing in thickness and giving off sideshoots of irregular shape which end blindly in the loose connective tissue and show no connexions with any organ.

The NSV layer and trunks consist of unipolar nerve cells of small size and uniform appearance. Their very thin axons unite in bundles which form nerves running to the vena cava. The total number of neurons of the NSV system, approximately estimated, must be over two millions. The disposition of the elements of this system is peculiar in that the axons of the cells situated in the caudal prolongations of the ganglionic trunks must run far rostralwards until they reach the nerves to which they contribute.

The nerves entering the vein penetrate through its muscle coat and form a network under the endothelial lining of the vein; this continuous neuropile layer extends from the anterior end of the vein to the entrance of the vena hepatica; all this part of the vein has on its inside longitudinal ridges formed by the uneven thickness of the neuropile layer.

The distribution of electric rays (Torpedo spp.) in northern European waters is discussed. Torpedo nobiliana is admitted as of regular occurrence; records of occurrence of T. marmorata are given in detail. The status in these waters of T. torpedo is doubtful. A synoptic key is provided together with illustrations of the three species.

The characteristics of the genus Pelagia are discussed.

It is concluded that two good species, P. noctiluca (Forskål) and P. flaveola Eschscholtz, are already described.

A third species P. colorata n.sp. has been erected for the medusa recorded from time to time from the coast of California which has been reported previously as P. noctiluca var. panopyra.

Meiobenthos, here defined as metazoans passing through a ½ mm screen, is described from core samples collected on muddy grounds at 100-140 m depth in the North Sea and off the west coast of Scotland between February 1962 and August 1963.

Sixteen cores of 2·2 cm diameter were collected from Loch Nevis, and 14 from the Fladen ground. The top 7 cm of each core was passed through a 500μ then a 76μ screen. The residues were examined entire, and the nitrate of the finest mesh was subsampled.

The fauna consisted mainly of nematodes, kinorhynchs, ostracods, copepods, polychaetes, and lamellibranchs. Between 61 and 97 % of the population consisted of nematodes, but copepods were second in importance and were more abundant than recorded on other subtidal grounds.

The fine mesh (76μ) retained almost all specimens of every animal group except Nematoda. Numerically 38% of the nematode population passed through the fine sieve, but this represented only 18% by weight.

The mean dry weight of meiobenthos on Fladen was calculated as 0·76 g/m2 and the average number of individuals was 196 × 104/m2.

In Loch Nevis the corresponding weight was 1·28 g and the number 101 × 104. The loch had a larger and more varied population of all groups except nematodes, which were particularly abundant on Fladen.

The data do not indicate significant population fluctuations throughout the year in the permanent meiobenthos.

Compared with other subtidal grounds Nevis and Fladen seem to support much richer populations, and the high values for Fladen are of particular interest since this is a poor macrobenthos area.

An attempt is made to indicate the possible level of meiobenthos productivity and it is suggested that there may be competition between meio- and macrobenthos for available organic matter which could result in a less efficient production of fish food.

Freezing-point measurements were made of blood samples taken from specimens of the marine wood-boring isopod Limnoria that had been exposed to sea water of various salinities for 2-3 days. Most of the work was done with L. (L.) tripunctata Menzies, but some preliminary experiements were carried out with L. (L.) lignorum (Rathke) and L. (L.) quadripunctata Holthuis.

It was found that the freezing point of the blood averaged 0·17°C above that of the external of medium in both hyp- and hyperosmotic environments. In the absence of any obvious factor which could explain this discrepancy, it is assumed that Limnoria has a certain degree of control over its blood concentrations.

Further experiments showed that the blood concentration fell as soon as the animal was introduced to the reduced salinity and levelled off at the hyperosmotic value within a few hours. There was some evidence of a periodicity in the osmoregulation.

The possible energetics of osmoregulation in Limnoria are discussed and it is concluded that the amount of energy utilized in the process is unlikely to make any significant inroad into the energy resources available for boring activity.

Free-swimming planktonic larvae of most species of sedentary marine invertebrates do not metamorphose in mid-water and settle at random, but possess considerable powers of delaying metamorphoses until a suitable substrate is encountered. Within recent years several workers have analysed the physical properties of a substrate to which larvae respond, particularly amongst those species which are restricted in their distribution in the littoral zone to the surfaces of other animals and plants. The serpulid Spirorbis borealis occurs most abundantly on Fucus serratus; experiments conducted in which surfaces treated with extracts of F. serratus were offered as alternatives to untreated surfaces illustrated that the larvae settle on these extract-treated surfaces in significantly greater numbers. It has been demonstrated that this response is to some chemical substance derived from the alga rather than to changes in physical properties of the surface such as increased thickness of the overlying film, or changes in the surface texture. Contact with this substance modifies the settlement behaviour from that observed amongst larvae settling on untreated surfaces. The photopositive behaviour is curtailed, and the duration of the crawling behaviour preceding settlement abbreviated. The precise mechanism by which the larvae respond to the active substance is as yet unknown, but observations have illustrated that it is dependent upon the larvae detecting the active substance as an adsorbed layer on the surface rather than a response to concentration gradients in solution. The significance of an innate ability to detect specific substrates by chemical structures characteristic of the surface in the speciation of the Spirorbinae has been discussed.

The growth in culture of Laminaria saccharina (L.) Lamour. and a species from Nova Scotia, tentatively identified as L. agardhii Kjellm., has been compared. Several characters, normally used for specific distinction within the genus Laminaria, have been shown to be modified by environmental conditions. These all concern the lamina and include the following: general morphology and texture, the shape of the base, the anatomical construction and the presence or absence of mucilage canals.

The question of the identity of L. agardhii from eastern and western Atlantic coasts is discussed.

Total fat, carotenoids, and vitamin A were determined physicochemically in sixty-nine species and fifteen generic groups of pelagic marine copepods.

Vitamin A was definitely present in Euchirella curticauda and Gaetanus kruppi and possibly so in Gaetanus pileatus and in a sample of Gaetanus spp. No vitamin A activity for vitamin A-depleted rats was found in fractions from a lipid extract of 1854 g of Calanus finmarchicus.

The significance of these findings is considered in relation to the high vitamin A reserves in many fish preying upon pelagic copepods.

The lower limit of the Laminaria hyperborea (Gunn.) Foslie zone is probably not always determined only by lack of sufficient light, even when a suitable substratum is present (Kain, 1962). It also appears that the establishment stage is critical although growth conditions deteriorate with depth (Kain, 1963). It therefore seemed desirable to determine exactly what the light requirements of the various different early stages were, and relate these to what could be found out about the light penetration in the natural habitat. The effect of temperature on these stages is also of interest, in relation to the seasonal cycle as well as to the geographical distribution of the species. In this study two different techniques were used: culturing the gametophytes on cover-slips and also studying changes in oxygen concentration as measured by the Winkler method.

The gametophytes of the different members of the Laminariales show a similar general course of development. A zoospore from a fertile frond of a Laminaria plant loses its motility, rounds off, swells and produces a tube with another sphere at the end into which all the cell contents pass (Killian, 1911). This process can be carried through in the dark but further development depends on light (Schreiber, 1930). In this genus the gametophytes are dioecious (Sauvageau, 1918; Williams, 1921) and equal numbers of male and female plants are produced (Schreiber, 1930). The female gametophyte may become fertile before dividing further (Sauvageau, 1918), resulting in a single egg, or may form a luxuriant filamentous structure which may produce many oogonia over a period of time (Ikari, 1921; Myers, 1925; Schreiber, 1930).

The general histology of the integument of the ophiuroid Ophiocomina nigra is outlined. Two types of integumentary mucous glands are described in detail for the first time. The first is a multicellular gland, the basal end of which is located deep within the calcareous layer of the integument. The source of the secretion is a variable number of nuclei embedded in a common cytoplasmic mass filled with fine basiphil granules. These cells contributed their secretion to a duct which pursues a tortuous course through the integument. The ducts frequently branch and anastomose so that any one exit pore may extrude mucin derived from a number of separate, polynuclear sources. The structure so formed is, thus, a massive, multicellular gland. Histochemical studies demonstrate that the mucin is a highly sulphated acid mucopolysaccharide. The second type of mucus-secreting unit is a unicellular gland usually located superficially in the calcareous layer or sometimes restricted to the epidermis and distributed universally over the body. The secretion product of these cells is shown histochemically to be a simple acid mucopolysaccharide. The mucin secreted by the tube-foot glands is demonstrated also to be a highly sulphated acid mucopolysaccharide.

The function of these secretions has been investigated to some extent. The massive glands secrete only under conditions of alarm and it is suggested that this mucus serves as a defence against predation. The unicellular glands secrete in a periodic fashion correlated with the act of feeding. This secretion is probably utilized in a suspension-feeding mechanism.

Experimental studies of plankton luminosity have been made with specially designed photomultiplier equipment; this records (on a Servograph Recorder) the flashes given off either by a sample of plankton or by individual animals placed in a container in a dark observation chamber. The apparatus is described.

Apart from preliminary laboratory records on the flashing of Beroë, Pleurobrachia and Pyrosoma, and record of the general luminosity in the sea at a depth of 62 m (made with an underwater version of the apparatus), the main work has been a laboratory study of the luminescence of dinoflagellates and of the euphausiacean Meganyctiphanes norvegica.

The dinoflagellate experiments showed the inhibiting effect of light, both natural and artificial, on luminescence, and the stimulating effect of mechanical disturbance which may override the former inhibition. A rise in temperature increased luminosity and cooling reduced it. A difference in the pattern of the luminosity of plankton samples containing dinoflagellates was shown by the introduction of actively swimming animals of different kinds. The dinoflagellates in the samples were mainly Peridinium depressum, Ceratium horridum and C. tripos var. balticum.

The Meganyctiphanes experiments showed a spontaneous flashing in seventeen out of twenty-seven tests and in one test the animals maintained such activity for the greater part of a 24 h period. In addition to their bright flashing, the photophores would at times keep up a dull glow for long periods (especially see the observations of F. Körte in the Appendix). Spontaneous flashing does not only occur in the breeding season as had been suggested by Mauchline (1960).

The original distinction between the Gadiculus populations of the east Atlantic and the Mediterranean was made on the basis of differences in pigmentation and vertebral count found in the larvae. A comparison of adult fish from the two areas shows that there are significant differences in body dimensions and also in certain meristic characters, particularly vertebral count. These differences are briefly discussed.

An apparatus and experimental method for the investigation of the effects of changes of pressure on the behaviour of marine animals is described.

In 43 of a total of 53 species examined in this apparatus definite responses to abrupt pressure changes of 1000 millibars or less have been observed, increased pressure generally causing increased activity and movement upwards or towards the light, and decreased pressure causing decreased activity and movement downwards or away from the light. The relative importance of light and gravity in the orientation of these movements is generally correlated with the degree of development of the light and gravity receptors in the species concerned.

The possible significance of these pressure responses in nature is discussed and it is suggested that pressure may be an important factor affecting the distribution of marine plankton, particularly during the hours of darkness.

The biology of whiting in Manx waters has been investigated at different stages of the life-cycle, with special reference to their diet. Planktonic postlarvae occurred chiefly in May, these measured between 4.5 and 16.5 mm, and had fed chiefly on Pseudocalanus. Larger whiting (between 21 and 52 mm) were taken in association with Rhizostoma. They were approximately 2–4 months old, and had fed on copepods supplemented with Hyperia and euphausiid furcilia. Immature whiting 77 mm long appeared in July in a shallow sandy bay—a nursery area. The fish were about 4–5 months old, and fed on swarming amphipods, isopods and mysids after dark, when these organisms were free-swimming. This diet was supplemented to an appreciable extent during the following April-June quarter by the inclusion of juvenile Ammodytes. After staying for nearly 1 year in the nursery area, the bulk of the fish appear to migrate to the open sea.

In the open-sea habitat, the immature fish fed chiefly on euphausiids, decapods and sprats—nektonic forms particularly. These whiting are themselves eaten by larger whiting in the same habitat. Adult whiting (over 220 mm) were taken only offshore, and fed chiefly on euphausiids, Crangon, Pandalus, Pasiphaea, Clupea and gadoids. A few samples taken off the east coast of I.o.M. indicated that the whiting are capable of feeding on infauna and plankton in an environment deficient in active epifauna and nekton. The whiting is an active feeder throughout the year.

Two length-weight relationships have been calculated for Manx whiting: nursery-area, and open-sea fish—the latter gain weight more rapidly than the former would be expected to do.

The structure and ciliation of the lip-apparatus of two species of Lima—L. hians (Gmelin) and L. excavata (Fab.)—and one species of Pecten—P. maximus (L.)—is described.

It is suggested that the lips of these three species of bivalves have been hypertrophied (and in one case partially fused) in order to retain particulate material being carried from the ctenidia to the mouth while at the same time allowing the escape of water currents, generated by the ciliary tracts of the ctenidia and palps, from the proximal oral grooves. Such water currents must emerge from between the lips of all bivalves but do not usually interfere with the passage of particulate material. In the Limidae and Pectinidae, these water currents have been intensified by the reduction of the anterior regions of the mantle cavity. Since this change in the proportions of the body can be correlated with the evolution of the monomyarian condition in the Anisomyaria, it is postulated that the lips of all monomyarian Anisomyaria will be similarly hypertrophied.

The oxygen uptake of eggs and larvae of Norwegian herring from Bergen (mean unfertilized egg dry weight about 035 mg) and of Baltic herring from Kiel (mean unfertilized egg dry weight about 0·10 mg) was measured by a reference diver and a Warburg respirometer. Anaesthetized Kiel larvae had values of about 0·10μl./larva/h and Bergen larvae 0·25μl./larva/h. When expressed as Qo (μl./mg dry weight/h) the values became Kiel 2·3, Bergen 2·5.

Oxygen uptake of embryos before hatching and of larvae, expressed as Qo, was most affected by activity, increasing in very active organisms by five to ten times the resting value of 1-2 μl./mg dry weight/h. Experiments to test the effects of temperature and salinity were done using anaesthetized larvae in some cases.

Temperature experiments with larvae gave a Q10 of about 2, the Qo, of anaesthetized Kiel larvae ranging from about 2·0 at 50° C to 35 at 14°C, and that of unanaesthetized Bergen larvae from 2·5 at 6° C to 50 at 140°C.

Eggs and larvae of both races reared in salinities from 5 to 50 %0 showed no detectable difference in oxygen uptake. However, abrupt transfer of anaesthetized larvae from one salinity to another caused violent fluctuations (by up to ten times) before adaptation took place. Buoyancy differences appeared to mask differences in oxygen uptake of unanaesthetized larvae in similar transfer experiments.

There was little tendency for oxygen uptake to become reduced during darkness in either Bergen or Kiel larvae.

The effect of age on oxygen uptake (expressed as Qo) was not marked, though there tended to be a peak at, and just after, hatching, with a tendency for a fall off during starvation.

Gases from the chambers of the cuttlebone have been analysed. Their partial pressures were never higher than those expected in the tissues of the animals.

In the older chambers the gas was about 97 % N2. The pressure of the gas in these chambers is always close to 0.8 atm.

These results are in accord with the theory that the gases play an unimportant role in the mechanism of the cuttlebone and merely diffuse into spaces created by forces other than gas pressure.

Observations have been made which can be used in studies of the life history and the rates of growth of cuttlefish in the Channel.