1. The seasonal changes in the population of Calanus in Loch Striven in 1933 have been investigated.

2. There were three main breeding periods. The first was in February and March, an unsuccessful beginning of the second in April, the true second brood in May to June, the third in July, and subsidiary broods in August and September.

3. Numbers were very low until April when the copepodites of the first brood caused a large increase; there was a second increase in May consisting mainly of the eggs of the second brood, and the maximum for the year came in July. The last and subsidiary broods provided the stock for the autumn and winter of 1933.

The possibility that certain plankton organisms retained by a stramin net may prove of value as indicators in elucidating the water movements at the mouth of the English Channel is shown.

The water populated by Sagitta setosa is shown to be clearly demarked from that in which S. elegans lives, the latter living to the west of the Channel mouth south of Ireland. The water in which S. elegans lives has here been called “western” water.

It is shown that the planktonic indicators for “western” water are Sagitta elegans, Sagitta serratodentata, Aglantha rosea, Stephanomia bijuga, Clione limacina, Meganyctiphanes norvegica, Thysanoessa inermis, and Cosmetira pilosella (in spring and summer only). Sagitta setosa is regarded as an indicator of “Channel” water. Muggiæa, Salps, Doliolids, Liriope exigua and Euchœa hebes are regarded as indicators of “south-western” water.

The geographical distribution of S. setosa is discussed. It is shown that it is probably a neritic species mainly confined to the English Channel and North Sea.

S. setosa predominates off Plymouth when the easterly element in the Dover Straits current is suppressed and the flow of Atlantic water into the North Sea from the north is strong (Carruthers' Theory). The two Sagitta populations swing to and fro off Plymouth so that, with a strong flow of Atlantic water into the North Sea from the north, the S. elegans population is pushed westward to the mouth of the Channel and S. setosa occurs off Plymouth.

During the course of the five years, 1930 to 1934, an agreement has been found between the occurrence or absence of concentrations of the diatom Rhizosolenia styliformis in the southern North Sea and the variations in the composition of the Sagitta population off Plymouth In the years in which Ehizosolenia, an indicator of Atlantic water, was abundant in the southern North Sea S. setosa predominated off Plymouth; when Rhizosolenia was absent S. elegans predominated.

These diatom concentrations have been shown by Savage and Hardy t o have an apparent influence on the movements of the Herring which is reflected in the landings at Yarmouth and Lowestoft.

The herring(Clupea harengus L.) deposits its eggs in the coastal waters around the North Atlantic Ocean, North Sea, and Baltic Sea. The salinity on the spawning grounds may vary from about 35%0 to 5%0. For instance, Brandhorst (1959) reports that successful spawning tookplace in the Kiel Canal in salinities down to 5%0, and Ford (1929) records that ripe herring have been found in the Tamar estuary. In a series of experiments Ford found that the eggs of herring could be successfully fertilized and incubated even in a salinity of 4·8%0. McMynn & Hoar (1953) investigated the effect of salinity on the development of the Pacific herringC. pallasii and found it had a wide tolerance, the lower level being somewhere between o and 6‰

In exploring a substratum, Balanus amphitrite amphitrite Darwin (Crustacea: Cirripedia) cyprids deposit ‘footprints’ of antennular secretion. The results of in vitro settlement assays suggest that in addition to serving as a temporary adhesive, the secretion acts as a pheromone, in that its presence induces the settlement of conspecific cyprids. This result is in accord with a previous study on Balanus balanoides (L.)(=Semibalanus balanoides). In settlement assays, the pheromone is likely to contribute to an observed positive linear relationship between settlement and cyprid density. The density effect should thus be an important consideration in the design of barnacle settlement assays. In the field, cyprid searching behaviour may render a surface more attractive to settlement by cypris larvae.

An account is given of the reproduction and development of the larva of N. diversicolor O. F. Miiller.

In any one population the number of males was found not to exceed 10 %.

The species is dioecious. Both sexes become green at maturity, but may be distinguished externally.

Ripe oocytes, which vary between 200 and 250μ in diameter mature in a loose coelomic parenchyma, and are released by rupture of the body wall after its partial histolysis. Sperm is released through the nephridia, or possibly by rupture of the body wall as well. In the male histolysis occurs, but the coelomic parenchyma is transitory. Sperm matures in the form of coelomic sperm plates.

The influence of sedimentation, depth and substratum angle on sponge assemblages in the Wakatobi region, south-eastern Sulawesi, Indonesia was considered. Sponge assemblages were sampled from two reef localities. The first reef (Sampela) was highly impacted by high sedimentation rates with fine sediment particles that settle slowly, while the second (Hoga) experienced only fast settling coarse sediment with lower overall sedimentation rates. Sponge assemblages were sampled (area occupied and numbers) on the reef flat (0 m) and at 5 (reef crest), 10 and 15 m (15 m at Hoga only). Some significant (P<0·001) differences were observed in the area occupied and the number of sponge patches between surface angles and sites. Significantly lower (t>4·61, df=9, P<0·001) sponge numbers, percentage cover and richness were associated with the reef flat at both sites compared with all other depths at each site, with the exception of abundance of sponges on the reef flat at Sampela, which was much greater than at any other depth sampled. Species richness increased with depth at both sites but differences between surface angles were only recorded at Sampela, with higher species richness being found on vertical, inclined and horizontal surfaces respectively. A total of 100 sponge species (total area sampled 52·5 m2) was reported from the two sites, with 58 species found at Sampela and 71 species at Hoga (41% of species shared). Multi-dimensional scaling (MDS) indicated differences in assemblage structure between sites and most depth intervals, but not substratum angles. A number of biological (e.g. competition and predation) and physical (e.g. sedimentation and aerial exposure) factors were considered to control sponge abundance and richness. Unexpectedly a significant (F1,169=148·98, P<0·001) positive linear relationship was found between sponge density and area occupied. In areas of high sponge coverage, the number of patches was also high, possibly due to fragmentation of large sponges produced as a result of predation and physical disturbance. The MDS results were also the same whether sponge numbers or percentage cover estimates were used, suggesting that although these different approaches yield different sorts of information, the same assemblage structure can be identified.

An account is given of a commonly accepted method for measurement of the gill area of fishes. A number of practical hints are included together with some warning about possible sources of error. In particular, these include sampling methods and reduction of errors due to shrinkage. Emphasis is given to the importance of weighting in the calculation of gill area. Problems which arise in comparisons of gills from different species are discussed and attention is drawn to possible errors that can be introduced by the reduction of all data to a given body weight offish. Such dangers are especially present where comparisons are made between fishes which may differ in weight by as much as four orders of magnitude.

The Preliminary Check-list (Parke, 1953), with the three subsequent lists of additions and corrections (Parke, 1956, 1957, 1959) was intended to provide a fundamental basis for the preparation of a Flora of the British marine algae sponsored by the British Phycological Society. Changes, both taxonomic and systematic, have been so numerous in recent years that a new Check-list is now necessary for the six Classes dealt with in 1953. Five additional Classes, marked below with an asterisk, are also included in the new list. As there is still controversy regarding the status and arrangement of the major algal groups they are here given, as in Parke (1953), the rank of Class.

This paper gives an account of a survey of the invertebrate populations (omitting Protozoa) of eight species of seaweeds on Church Reef, Wembury Bay, extending over the entire intertidal range.

Above high-water neaps the faunas are poor, except for that in Lichina pygmaea which is the richest in individuals on the shore.

Between high-water neaps and low-water springs the most numerous groups are copepods, acarines, young littorinids and (in Ascophyllum only) ostracods.

In the holdfasts of Laminaria digitata polychaetes are very abundant and make up the majority of the population.

The intertidal faunas are compared with those in the soil on land, and prove to be far more abundant. Even the most plentiful group in the soil, the insects, is rarely as numerous as it is in Ascophyllum around mean sea-level.

Altogether 177 species are recorded, of which 35 are not in the Plymouth Marine Fauna (1931).

An offshore and a littoral population of Echinocardium cordatum have been observed for a period of 7 years, starting from the time of their simultaneous larval settlement and establishment.

The littoral population was found in clean sand of low organic content. Individuals burrowed to a depth of 15 cm and could move through the sand at a speed of 6–8 cm/h. The test length increased at an average increment of 8 mm/annum. Breeding first took place in the third year and continued each year after.

The offshore population was found in very silty sand at depths of 30–40 m. Here individuals burrowed to a very shallow depth, 2 cm. or less, and moved very slowly through the sediment. The annual increment of test growth was only about 3 mm. Estimations showed that the littoral population had a production rate four times greater than the offshore. The offshore population did not reach sexual maturity during the period of observation. No new settlement was observed anywhere in the area during the period of observation.

The offshore population occurred in large discrete patches, each displaying a quantitatively concentric pattern with a central area of high density. Samples taken at single stations within the patch showed that the distribution was random for most of the year but that aggregations formed in June, July and August.

Both populations showed a steady mortality rate of about 15 % per annum and the longevity was estimated to be in the region of 15 years.

Based on prolonged aquarium observations of the feeding behaviour, reasons are given for believing that the surface collecting activities of the penicillate tube-feet of the anterior ambulacrum should be considered as a true feeding mechanism.

The demersal ichthyofauna of the continental slope of the Porcupine Seabight, eastern North Atlantic, was studied from 144 samples taken by three different types of otter trawl. At least 118 species from 43 families were represented among some 54,000 specimens collected from 247 to 2172m soundings. Collectively, the catches were dominated in species richness by the Macrouridae, Alepocephalidae and Squalidae and in abundance by the Synaphobranchidae, Macrouridae and Moridae. Separately, relative abundance of species was more similar between the two larger trawls, setting their catches apart from the smaller net. Gear selectivity evidently accounted for this variation, which was examined by an index we developed and call species fidelity. This accounts for patterns of continuous faunal change with increased soundings concomitant with variance in species adult size and mobility. In pursuance of a more accurate representation of relative biomass and abun-dance than achieved hitherto, the best estimate, within the limitations imposed by the sampling gears and regime, was derived from a combination of the mean values per 200m stratum of the two large trawls with the addition of those of the eel, Synaphobranchus kaupi, from the small gear. Tentative comparisons between these results and those from elsewhere suggest that the Porcupine Seabight is generally lower in biomass and similar or lower in abundance. It was concluded that an accurate indication of ichthyofaunal structure with increased soundings can only be achieved through a detailed knowledge of the size structure of each species over its entire sounding range synthesized from a multi-trawl investigation via analyses of species fidelity.

The intertidal actinian Anemonia sulcata is known to harbour yellow-brown algal symbionts which are similar in appearance to the zooxanthellae of hermatypic, or reef-building, corals and a number of other invertebrate species. The cytochemistry and structural morphology of the zooxanthella has been studied by light and electron microscopy, to help define it taxonomically and to reveal something about its relations with the actinian. These investigations confirm that it is a dinoflagellate and have revealed several structural adaptations which are formed as a result of the peculiar mode of life adopted by this alga. Of significance is the fine structure of the periplast, which may have a considerable bearing upon the type of relationship which can exist between the host and its symbiont. These findings are discussed in terms of other known instances of algal-invertebrate symbiosis.

This study reviewed published data on dietary preferences of beaked whales (Ziphiidae) from stomach contents analysis. Detailed data were only available for three of the six beaked whale genera (Hyperoodon, Mesoplodon and Ziphius). Stomach samples of these three beaked whale genera primarily contained cephalopod and fish remains, although some also contained crustaceans. Mesoplodon spp. were found to contain the most fish, with some species containing nothing but fish remains, while the southern bottlenose whale (Hyperoodon planifrons) and Cuvier's beaked whale (Ziphius cavirostris) rarely, if ever, contained fish. Of cephalopods identified, Histioteuthid, Gonatid, Cranchiid and Onychoteuthid species usually contributed most to prey numbers and biomass for all beaked whale genera. There was a wide range of species and families of cephalopods recorded from stomach contents, with no obvious preference for bioluminescent prey species, vertical migrating prey species or prey species with specific body compositions. Whales of the genus Mesoplodon generally contained smaller prey, such as cephalopods under 500 g in weight, compared with other beaked whales. Hyperoodon and Ziphius frequently contained much larger cephalopods with many important prey species having a mean weight of over 1000 g. This suggests that Mesoplodon occupies a separate dietary niche from Hyperoodon and Ziphius, which may be an example of niche segregation. In contrast, Hyperoodon and Ziphius appear to occupy very similar dietary niches but have geographically segregated distributions, with Hyperoodon occupying cold-temperate to polar waters and Ziphius occupying warm-temperate to tropical waters.

Infauna diversity is reported from the Sabellaria alveolata reefs in the bay of Mont Saint-Michel in France, known as the greatest European reef formation. Polychaetes dominate the fauna, but other species also play a role in terms of reef functioning. Species richness of the associated infauna is much higher than that of the surrounding sediments and is concentrated mainly on the reef surface. Species richness clearly varied according to the three stages of reef evolution: the ‘degraded’ reef stage is different from the ‘ball-shaped structure’ and ‘platform’ stages. Multivariate analyses indicate that three species communities can be distinguished, each corresponding to a different stage of reef development. The number of species is very high, but only a few species are restricted to a particular reef stage. Variations of surface topography and spatial heterogeneity can explain unusual associations of species that make infauna associated with S. alveolata reefs very unique.

Moreover, the high densities of S. alveolata (up to 60,000 ind m−2) raise questions regarding the role of the reefs in the ecosystem of the bay. Anthropogenic influences, notably mechanical disturbances due to fishing activity, show a steady increase and may have a serious impact on the assemblage diversity and the ecological stability of the reef, even though recolonization of S.alveolata is possible in degraded reef areas. An important question that must be addressed is whether human activities could influence the role of S. alveolata reefs in the bay of Mont Saint-Michel.

Collections of some 22,000 female and 6000 male Crangon vulgaris were made throughout the year from the shrimp fisheries of the Severn Estuary and Bristol Channel. All animals were measured.

The habits of the species are described; it can withstand a wide range of temperature but, though euryhaline, resembles other Decapoda in the inability to withstand low salinity combined with low temperature.

Osmo-regulation is apparently largely inhibited at low temperatures and to a greater extent in the males than the females.

Growth rate decreases with increasing age; in the female there is no increase in length when moulting from the ' neuter' to the egg-carrying intermoult. The duration of this intermoult, if spawning is successful, is about double that of the normal intermoult under the same temperature conditions. Growth almost ceases in the winter.

Secondary sexual characters are described, especially the differences between the endopodites of the pleopods in the two sexes.

Females become mature at a minimum length of 45 mm. in the Channel and seldom less than 50 mm. in the Estuary. The effect of the female sexual cycle on the size of the ovary and the form of the pleopods is described. The process of copulation is described; it can occur in the brackish waters of the estuary. Egg-laying always follows within two days of moulting into the egg-carrying condition but eggs are not retained if copulation has not occurred.

The females lie on their sides during the act of spawning and the eggs are firmly attached within thirty minutes to the egg-carrying setae on the basipodites of the first to fourth pair of pleopods, then to those on the endopodite of the first pleopod, finally to those on the coxopodites of the last two pairs of pereiopods.

The vertical migration of two Euglena species and several diatom species into and out of the sediment on the banks of the River Avon has been studied under natural conditions. All species have been shown to migrate vertically upwards when exposed during daylight. Tidal flooding of the sediment is generally preceded by re-burrowing of the algae beneath the surface. Methods have been devised to follow these migrations in both the field and laboratory. Laboratory experiments show that these migrations are rhythmic, continuing under constant illumination and temperature and removed from tidal influence. The effect of three different temperatures and three different light intensities has been investigated. Transfer from low to high temperatures has been shown to reset the phase of the rhythm. The results are discussed in relation to other work and to the ‘biological clock’ hypothesis.

Competition for space between sessile animals on the seashore and sublittorally is an important factor in their ecology. This is partly because of their density, but also because competition for space between sessile animals is of a more severe kind than occurs between free-living ones, for they cannot move away from their competitors.

Five species of bresilioid shrimp were investigated at seven hydrothermal sites on the Mid-Atlantic Ridge: Menez Gwen, Lucky Strike, Rainbow, Broken Spur, TAG, Snake Pit and Logatchev. Samples were prepared for analysis of stable isotopes, elemental composition and lipids. Shrimp behaviour was observed from the submersible ‘Alvin’ and in the laboratory aboard RV ‘Atlantis’. The distribution and zonation of the shrimp species was recorded. Juvenile shrimp of all species arrive at the vents carrying reserves of photosynthetic origin, built-up in the pelagic larval stages. These reserves are used while the shrimp metamorphose to the adult form and, in Rimicaris exoculata and Chorocaris chacei, while they develop epibiotic bacteria supporting structures, the modified mouthparts and the inside of the carapace. The main food of adult R. exoculata is filamentous bacteria that grow on these structures. The intermediate sizes of C. chacei also feed on such bacteria, but the final stage gets some food by scavenging or predation. Mirocaris species scavenge diverse sources; they are not trophically dependent on either R. exoculata or mussels. Adults of Alvinocaris markensis are predators of other vent animals, including R. exoculata. The dense swarms of R. exoculata, with their exosymbionts, can be compared to endosymbiont-containing animals such as Bathymodiolus and the vestimentiferan tube-worms of the Pacific vents. Such associations, whether endo- or ectosymbiotic, may be necessary for the development of flourishing communities at hydrothermal vents.

A gregarious tendency during settlement, similar to that already demonstrated in oyster larvae, was suspected in Elminius, because cyprids settled in groups during the initial stages of colonization of surfaces (crowded later arrivals showed a spacing-out tendency) and because settlement on test-plates was peculiarly sparse at stations with a muddy bottom, where barnacles were absent.

Settlement was much heavier on areas of smooth glass, which already bore recently settled barnacles, than on similar adjoining areas which were bare.

When barnacled microscope slides were stuck to one set of glass plates, bare slides to another and the two sets exposed side by side, settlement was consistently much heavier on the plates which bore the barnacled slides. The mean density of settlement on the bare slides and the surrounding plates was uniformly low, except for a greater density immediately adjoining the slides, probably due to sheltering alongside their edges. On the barnacled slides density of settlement was much higher and on the plates immediately alongside still more so, whilst at increasing distances from the slides it became gradually smaller but was still much heavier than on the plates with the bare slides. This suggests that the sensory basis for gregariousness can act at a distance. It may possibly be olfactory.

In view of the fact that dogfishes are now of undoubted importance as marketable food fishes, it is necessary that the life-history of each of the species concerned should receive closer attention than hitherto. The present publication is the result of an endeavour to gain a personal working knowledge of the general life-history of the species which are landed at Plymouth. In carrying out a scheme of work of this kind it is certain that many of the observations made will have already been carried out previously by other workers, but, nevertheless, the results obtained are of value, not only in regard to the degree of confirmation which they afford, but also in the building up of an account of the life-history under the local conditions. In some instances, too, it will be seen that the actual numeric results in themselves are of little statistical value, but they yield very interesting suggestions which may be confirmed or disproved by a repetition of the experiments on a larger scale. I express my thanks to the fish-buyers at Plymouth fish-market, particularly Mr. J. Vanstone, for their kindness in allowing me to handle their fish before dispatch, and for their assistance in obtaining a regular supply of material for many months.