A long-established population of Jaera hopeana living ectocommensally upon Sphaeroma serratum is described from Wembury. This is a new record for the British fauna and is the northernmost record of a species which is found predominantly in the Mediterranean and Black Sea.

Sporophytes of Laminaria hyperborea have been grown under various conditions in the laboratory up to the stage of 1000 cells. Some larger plants have been observed after exposure in the sea. Growth was not increased by artificial aeration of the normally stagnant cultures, nor by introducing a dark period each day. The cell number per sporophyte was found to increase exponentially with time. In from 10- to 1000-celled plants the logarithm of the cell number was proportional to the logarithm of the plant length; the relationship corresponded to two-dimensional growth in the presence of increase in cell length. In this size range, when the plants were mainly monostromatic, the growth rate in the laboratory was 0.5 cell divisions/day and 22% increase in length/day. The growth rate of larger sporophytes, partly polystromatic, in the sea, was 10% increase in length/day. A sporophyte would take at least 54 days from the release of the parent zoospores to reach a length of 1 cm. The minimum continuous irradiance necessary for growth was 2 μg.cal/cm2sec (20 lux) at 10° C and 4–5μg.cal/cm2sec (40–50 lux) at 17° C. The saturating continuous irradiance was at about 100 μg.cal/cm2sec (1000 lux) at 10° C and about 150 μg.cal/cm2sec (1500 lux) at 17° C. Up to 360 μg.cal/cm2sec (3600 lux) from fluorescent lamps was not inhibitory. Growth at 15–20° C was approximately the same as at io° C.

The feeding mechanisms of Ophiocomina nigra have been re-examined. A new mechanism, the mucus-net method, is described for the first time. This is essentially a method of suspension feeding in which seston is trapped in a net of mucous threads between the arm spines. The entangled material is formed into boluses by simultaneous activities of ciliary currents and the tube-feet and is transported to the mouth by the tube-feet.

Praunus inermis (Rathke) breeds at all times of the year in the Clyde, the pro-portion of breeding females being minimal in January and maximal in August. The progeny produced by the winter stock during the period March to July are known as the summer generation, the eldest members of which commence breeding in July/August, and the new winter stock is formed in the autumn from the surviving members of this generation and their progeny. The number of young carried in the marsupium varies seasonally, being about 30–40 in May/June and 10 during the period November to January. Larger females tend to carry more young than smaller females. Comparisons are made between the population in the Clyde and those at Port Erin, Isle of Man, and at Nyborg Fjord, Denmark.

The known distribution of the Northern Rockling, Ciliata septentrionalis (Collett, 1875) is discussed and several additional occurrences reported. These greatly extend the range of the species. Notes on the biological background of the fish are provided, as are synoptic descriptions of it and its relative C. mustela.

The respiration of Limnoria was measured manometrically in sixteen solutions ranging from 6% to full strength sea water (36%). In a second series of experiments, simultaneous measurements were made in full strength sea water and in dilutions of 7, 14, 21 and 28% respectively. No significant correlation was found between the respiratory rate and the degree of dilution of the medium.

The rate of cirral beat of Balanus balanoides is related to the logarithm of the body weight as an exponential function. In any one animal, there is little effect of temperature on cirral activity between 7·5° and 10° C. Between 10° and 20° C, however, there is a rapid increase in cirral beat with temperature followed by a fall at temperatures above 20° C.

Balanus balanoides exhibits a fast, medium and zero rate of oxygen consumption. These rates of oxygen consumption correspond with (a) normal cirral beating, (b) ‘testing’ activity with no cirral movement, and (c) with the closure of the mantle cavity. Both of the possible levels of oxygen uptake are related to the logarithm of the body weight in a logarithmic fashion over the temperature range 7·5°–22·5° C. Temperature affects the two rates of oxygen consumption differently. In the slower rate (rate B) there is an increase in the rate of oxygen consumption between 7·5° and 14° C but there is no significant increase in the rate of oxygen consumption between 14° and 22·5 C°.

This research has been concerned with the movement of pigment in the occlusible tapetum lucidum of the spur dog Squalus acanthias. The pigment expands and covers the reflecting plates of the tapetum in light, and retreats and uncovers the plates in darkness. Movement of pigment in one eye occurs independently of that in the other. Normal movement of pigment is not affected by cutting the optic nerves and oculomotor nerves, by sectioning the cord immediately behind the medulla, nor by excising the pituitary and pineal glands. It is concluded that the process is not under nervous or hormonal control. It occurs normally in excised opened eyes that are kept in oxygenated Ringer solution, but not under partial or fully anoxic conditions. The pigment cells of the chorioid seem to be behaving as independent effectors, sensitive to light. The pigment expands in tapeta freed of retina, in light or darkness. No explanation is yet available for the latter anomalous result. Measurements were made of the reflectivity of isolated tapeta, and curves are presented showing the progressive decrease of reflectivity accompanying expansion of pigment, and changes in the colour composition of the reflected light.

A method is described for staining the musculature of preserved salps with Rose Bengale and reforming their natural shape by injecting the body cavity with molten agar. Compared with normal preserved material, specimens prepared in this way are easy to handle, more lifelike in appearance and the detailed arrangement of their musculature is clearly differentiated in three dimensions.

Details are presented here of four species of amphipod from Norfolk waters, including descriptions of Melita reidi sp.nov. and of Parapleustes sp., as well as comments upon an unusual young Siphonoecetes sp., and on a population of Amphilochus spencebatei. The Melita is very small, pale and blind, and apparently lives interstitially.

During a study of the amphipods of Norfolk (in preparation for publication) a species of amphipod apparently new to science has been found, and is described below; comments are also made here on the taxonomic characters of three other species found locally. The area concerned (including a station list) is described by Hamond (1963).

Records of cirral activity have been made over periods of 24–48 h for individual specimens of eight species of barnacles from three different localities. The effects of movement, gas content, and hydrogen-ion concentration of the water have been studied.

In still water most species eventually settle down to a more or less steady rhythm (activity rhythm) of short bursts of cirral beating interspersed with inactive periods. Two exceptions are the surf- or current-loving species Balanus cariosus and Tetraclita squamosa which remain inactive or eventually cease activity. In moving water all species show practically continuous activity, the velocity of the flow needed to produce this response varying according to the species, habitat, and previous history of the specimen. Increased oxygen content has less effect on activity than other factors studied, but eventually appears to reduce activity. A gradual reduction in oxygen content first leads to increased activity and then signs of distress attributable to anoxia.

Nitrogen excretion by Calanus finmarchicus (Gunnerus) and C. helgolandicus Claus collected at Millport and Plymouth has been measured under various experimental conditions.

Adult females feeding on Brachiomonas submarina, Cricosphaera elongata and Skeletonema costatum at cell concentrations corresponding to the mean annual level of particulate nitrogen in Plymouth Sound excrete 12·4, 9·0 and 6·4 μg N/mg dry body weight/day respectively. When the concentration of food is raised, as might occur during a spring outburst of phytoplankton, there is an increase in the quantity of nitrogen excreted. On the other hand, nitrogen excretion rapidly diminishes in the absence of food.

The problem of how a fish can make itself invisible in the natural light-conditions in an aquatic environment is discussed with particular reference to the silvery surfaces of fish.

In fish which we have examined, the silvery surfaces are of two types: (1) an argenteum which consists of long thin crystals of guanine whose reflecting surfaces are approximately parallel with the surface of the fish; (2) layers of guanine crystals lying either on the inner surfaces of the scales or in the subdermis—these crystals are not, in general, orientated with their reflecting surfaces parallel with the surfaces of the fish, and are much broader than those of the argenteum.

Methods are described by which the orientation of the crystal planes with respect to the planes of the scales on which they lie can be determined.

The orientation of the crystals of type 2 in different parts of the body is described for the horse mackerel, Trachurus trachurus (L.), and for the bleak, Alburnus alburnus (L.).

For the bleak it is shown that although the planes of the crystals are often very much inclined with respect to the planes of the scales, the long axes of the crystals are always approximately parallel with the planes of scales. The inclination of the crystals, therefore, is away from the scales across their short axes.

Measurements of the light transmitted by silvery scales of the bleak show that they reflect light strongly when this falls obliquely on the crystals which they contain and that they are most transparent to light which strikes the scales in a direction perpendicular to the reflecting planes of the crystals.

The distributions of four species of larval Ammodytidae in the Southern North Sea are described. Two separate broods of Ammodytes lancea larvae were found, in spring and autumn. The spring larvae occurred in the areas of the Thames and Wash, and the autumn type mainly off the French and Dutch coasts.

A description of these larvae is given. Larvae of Gymnamtnodytes semisquamatus were found in the Southern Bight area and in several areas off the Humber. Few larvae of Ammodytes lanceolatus were taken: they occurred in the Southern Bight and Dowsing areas. A. marinus larvae were found in two areas off the Humber and in the Southern Bight. There is evidence for a spawning area some distance to the west of the Dover Strait.

The hitherto unknown hydroid of the anthomedusa Neoturris pileata has been found abundantly in the Clyde Sea Area, and medusae from it have been reared. The hydroid and the stages of development of the medusa are described and figured. The medusa is commonly present in the plankton in this area.

A method is described for measuring, for various angles of incidence, the polarization produced by reflexions from natural surfaces.

This method was tested by measurements on matallic surfaces of known properties and then used to study reflexions from the silvery gill cover of the bleak Alburnus alburnus (L.).

Althouth the reflecting surfaces of the gill cover are crystals of a dielectric guanine, there is no polarizing angle, and the reflecting properties of the gill cover resemble those of a sputtered aluminium mirror

The biological significance of these results is briefly discussed.

A system of nerves (called for short NSV system), described previously in Eledone cirrosa, whose only task appears to be the formation of a fine neuropile in the vena cava, is present also in Sepia officinalis It has a similar disposition to that in Eledone but shows certain special features. It is composed of neurons the cell bodies of which are located in a layer (NSV layer) of the visceral lobe of the brain and in the paired ganglionic trunks, termed the lateral and medial NSV trunks, which emerge from the visceral lobe with the posterior infundibular and visceral nerves respectively. After accompanying these nerves for some distance these trunks take an independent course and give off some tapering branches ending blindly in the loose connective tissue.

Observation of Balanus balanoides on the shore at Whitstable shows that at all tidal levels a percentage of the animals maintain a connexion between the mantle cavity and the air by means of a minute aperture or pneumostome. A higher percentage of animals at lower shore levels have a pneumostome than those nearer the top of the shore.

The orientations of the reflecting layers in the external surfaces of the herring have been found both by light-measurements on the fresh fish and by histological studies on preserved specimens.

The reflecting platelets which lie under the scales are orientated, with respect to the surface of the fish, in a similar way to the platelets found in the bleak and described earlier by Demon & Nicol (1965). However, on the curved dorsum of the fish, although the reflecting platelets are much more perpendicular to the sea surface than the scales on which they lie, these platelets are still inclined some 20° to the perpendicular. It is shown that, in this region, the fish reflects the fraction of the light striking the platelets which is sufficient to match the background against which the fish is seen. The platelets on the curved dorsum have the property of reflecting green light well if it falls obliquely on them but reflecting it poorly when it strikes them at angles close to normal incidence. On the broad flank of the herring the scales have reflecting platelets under most of their surfaces, and the individual scale has several distinctly coloured regions. When we look at any particular region of the flank of an intact fish we are always looking at several overlapping layers differing greatly from one another in their spectral reflecting properties.

It is the combination of the reflexions of several layers which gives the very bright silvery reflexions of the intact fish. A system of overlapping scales of this kind is needed even to reflect one waveband of light well over a wide range of angles of incidence.

The seasonal changes in the foraminiferid populations along the Tamar-Eddy-stone profile have been shown for the winter, spring and summer of 1962. No single environmental factor appears to be wholly responsible for these changes but temperature is considered to be important. Variable salinities are of secondary importance in the Tamar. These seasonal changes have been compared with those observed at Christchurch and found to be different, presumably because of the different temperature and salinity conditions prevailing in the two estuaries.

A qualitative assessment of the energy input of the environment from the nature of the deposited sediment has shown a good positive correlation between the distribution of the Miliolacea and a high-energy environment. All other superfamilies show a negative correlation with high energy, but the Cassidulinacea show a preference for a moderate-energy environment during the summer.

Foraminiferids, found not to be very abundant in the Plymouth region, show a trend toward greater numerical abundance and greater diversity in passing out o t sea. The shortage of living foraminiferids is tentatively correlated with a restricted food supply.