The concept of external metabolites in the sea, which has received support from biological investigations, invites chemical corroboration which, until recently, has not been forthcoming. Separations of organic matter from filtered sea water using a variety of methods are reported and a preliminary assessment made. Organic residues obtained from different open sea sources by adsorption on carbon give rise to different paper chromatogram patterns. Certain organic components of a carbon adsorbate contain substances which affect the growth of a number of marine phytoplankton organisms. Further research is planned employing methods of isolation and chromatography of the dissolved organic matter from different sea waters and the assessment of biological activity of certain fractions by means of common marine organisms. Some aspects of the significance of biologically active compounds in the sea are mentioned.

A description is given of the commonest sublittoral algae and sessile animals found on rock at Stoke Point Reef and at the E. Blackstone rock near Dartmouth to a maximum depth of 28 m. The E. Blackstone fauna resembled that of Plymouth Sound. The marked change which has been found is ascribed to the greater turbidity of the water near Dartmouth and the increased shelter from wave action.

The jelly-fish Aurelia aurita possesses external and internal ciliary currents that play a large part in food collection and in the transport of food, reproductive products and excretory matter.

Adults feed on relatively small organisms, which are collected in mucus on all external surfaces and eventually passed to the inner surfaces of the oral arms.

The inner surfaces of the oral arms bear two ciliated tracts which operate simultaneously in opposite directions. The lateral tract carries food materials proximally towards the gastric pouches, but is capable of rejecting inedible matter. The basal tract carries excretory matter distally, away from the gastric pouches and canals to the exterior.

Rejection reactions are also found in the gastric pouches and radial canals, parts of which have currents moving in opposite directions on the roof and on the floor. These opposing currents appear to be derived from the system in the ephyra stage, where the circulation in the wide gastric cavity and blind-ending canals is maintained partly by centripetal currents on the floor and centrifugal currents on the roof.

The directions of the main currents remain constant throughout the larval stages to the adult, although slight variations are introduced by morphological changes. The currents also remain the same during spawning, when the eggs and sperm leave the gastric pouches by the normal excretory path.

Many of the ciliary currents found in Aurelia are present in other semaeostome and rhizostome medusae, but only in Aurelia do the umbrella surfaces and currents play a large part in food collection.

Kidneys of Lophius piscatorius L., perfused with heparinized blood, respond to a high tension of CO2 in the blood by a drop in urine flow and in their capacity for concentrating Mg. At the same time, but independently, CO2 reduces the blood flow. Both cyanide and fluoride may stop or reduce water secretion and Mg concentration, according to the concentration used, showing that both these activities are dependent on aerobic processes and presumably on the integrity of the carbohydrate cycle.

The results of analyses of water from the International Hydrographic Station EI during 1954 are discussed. The seasonal variation is shown, in which it appears that consumption of nutrients in the spring outburst of plants was: phosphate 0.37μg atom P/l., total phosphorus 0.26μg atom P/l., silicate 2.49μg atom Si/1., these figures being means for the whole water column. Unusual changes in silicate concentrations between January and February,and between August and September, are ascribed to changes in the water mass at the station. This conclusion is supported by the temperature, salinity and phosphate.observations.

A bacteria-free culture of the important centric diatom Skeletonema costatum has recently been established at Millport, and some exploratory nutritional experiments have been carried out with it. S. costatum is a photo-autotroph whose autotrophy is, apparently, limited to cobalamin (vitamin B12).

Details concerning isolation and maintenance of S. costatum differ from those already published (Droop, 1954a, 1955) only in the matter of pH control, a vital factor in the successful culture of this species whose range of tolerance is narrow (pH 7–5–8–5).

Six common supra-littoral Protista from the island of Cumbrae are described and details given of their cultivation. Chlorophyceae: Nannochloris oculata n.sp., Brachiomonas submarina var. pulsifera n.var.; Cryptophyceae: Hemiselmis virescens n.sp.; Chrysophyceae: Syracosphaera elongata n.sp., Microglena arenicola n.sp., Mallomonas epithalattia n.sp.

In a recent short note in this Journal (Fraser, 1954) the occurrence was announced, off the entrance to the English Channel, of the solitary form of the salp Ritteriella picteti (Apstein), and seven aggregate forms of R. amboinensis (Apstein), taken by H.M.S. Challenger in 1953. The identification of the aggregate forms as R. amboinensis and not as R.pictetiv/as based, as then stated, on Thompson's (1948) description from a very young specimen of R. picteti which emphasized the similarity of its muscle arrangements to those of Salpa cylindrica and not to Ritteriella amboinensis.

Since this was written, Berner (1954) has described the aggregate form of R. picteti from good specimens found off the west coast of U.S.A., and he has shown that the musculature was in fact not like that of Salpa cylindrica but very similar to Ritteriella amboinensis. Differences were noted in the number of fibres constituting the various body muscles and in the number and arrangement of the oral muscles. A still more recent paper by Yount (1954) includes comparisons of the two forms, based on Berner's characters but also including differences in the length of the endostyle and in body shape (length of anterior and posterior processes, and degree of extension of the gut outside the rest of the body). Yount also goes into greater detail in describing the oral musculature in tie two species.

A re-examination of the specimens taken by H.M.S. Challenger shows them to be in fairly close agreement with both Berner's and Yount's descriptions of R. picteti, but with one or two small differences. The actual number of fibres in the muscles is rather smaller than given by Berner for R. picteti, though the precise figure is difficult to ascertain, and there is no median interruption of the first sphincter muscle in the upper lip which Berner believed to be characteristic, and which Yount accepted.

Rothschild (1935) reported that Dr M. V. Lebour drew her attention to a ‘huge-tailed’ monostome which had occurred during 1931 in specimens of Turritella communis collected from the Rame Mud, Plymouth. From 1932 to 1934 Rothschild (1935) examined 541 specimens of this gastropod from that locality without finding this larva. During the summer of 1952, the present author examined a number of specimens from the same locality and was also unsuccessful in finding such a larval trematode. However, in November 1952, the monostome described below was found in two of 110 Turritella collected from Cawsand Bay, Plymouth Sound.

The author wishes to express his indebtedness to the Director and Staff of the Plymouth Laboratory of the Marine Biological Association for their friendly co-operation and assistance in all phases of this work. The work was carried out while the author was holding a Fulbright Scholarship.

METHODS

Fully developed cercariae were obtained by isolating infeaed specimens of T. communis in jars of sea water and allowing the cercariae to emerge. Rediae and immature cercariae were obtained by crushing the shells of the hosts. Living specimens as well as permanent preparations were studied. Whole mounts were fixed in sublimate, stained with borax-carmine, and mounted in Canada balsam, or fixed in sublimate or formalin, unstained, and mounted in Faure's medium or in Cristalite (E. Gurr). Serial sections (5 /x) of several cercariae were stained with Ehrlich's haematoxylin and eosin. The orientation of the objects in the desired position at imbedding was achieved by the method of Peterfi (after Romeis, 1948, p. 99). The incidence of infection was determined by crushing the gastropods and examining the digestive glands and gonads under the dissecting microscope.

Living specimens of Petricola pholadiformis Lamarck were obtained from Burnham-on-Crouch, Essex.

Studies of the principal organ systems were made on the living animal, particular attention being paid to the ciliary feeding and cleansing mechanisms in the mantle cavity, and the ciliary sorting mechanisms within the stomach. The action of the bulbus on the posterior aorta was also studied.

A detailed comparison was made between P. pholadiformis and all the British species of Pholadidae. Thirty anatomical features were found in which P. pholadiformis differed from all of the Pholadidae, and fourteen features in which P. pholadiformis resembled one or more species of Pholadidae. It was concluded that these resemblances were purely fortuitous.

The optic cushion of Marthasterias glacialis is seen to contain yellowish orange and reddish orange pigments. The former occurs throughout the cushion, the latter is confined to the wall of the optic cups and a few scattered, irregular patches. Both pigments occur in the cytoplasm of long and narrow or irregular cells, some in the form of granules or vacuoles.

Optic cushions yield an orange extract in methanol which decomposes in light.

The behaviour of methanolic extracts after partitioning, saponification, chromatographic separation and spectrophotometric examination indicates the presence of β-carotene and esterified astaxanthin.

The significance of the results in relation to previous findings and their possible bearing on photoreception is discussed.

The logarithmic transformation has been used in the statistical analysis of certain marine biological data. Parameters calculated from the transformed distributions have been used in the description of the observations, but it appears that some of the mathematical procedures adopted have not been fully understood.

Winsor & Clarke (1940) have analysed data from plankton hauls. The problem considered by them was the determination of the variability in numbers of animals caught by repeated hauls through the same body of water. The raw data were characterized by a constant coefficient of variation, i.e. the variability in catch was proportional to the size of the catch. By transformation from the actual numbers caught to their logarithmic values, it was possible to equalize the variances and to apply the method of analysis of variance to esti-mate the variability due to the different sources. Finally, an estimate of the coefficient of variation was obtained from the logarithmic values. Their method of estimation was quoted by Snedecor (1946, p. 451) and was employed by Barnes & Bagenal (1951) in their study of repeated trawl hauls. Barnes & Bagenal also calculated confidence limits for comparison of observations following the method of Silliman (1946) in his work on pilchard eggs. These methods seem to be based on a misunderstanding of the nature of a trans-formation. The formal relation between the variance of such transformed data and the coefficient of variation of the untransformed data follows from the moments of the ‘log-normal’ distribution, given first by Wicksell (1917). From these moments it will be shown that the method given by Winsor & Clarke is mathematically unsound.

The ages of 1426 female, and 135 male Long Rough Dabs have been determined from otolith readings. The females were found to live into their seventh year and reach 30.5 cm, compared with males that live to their fifth year and reach 19.0 cm in length. However, the mean increase in length per year for a given length, has been found to be the same. The growth of the females has been shown to fit the equation lt=26.437 (I—0.574t) and of the males lt=17.754 (I —0.585t). In the case of the females the observed and calculated values agree quite closely, but with the males there is a greater difference, and it is believed that the discrepancy is due to net selection. The suggestion is made that the calculated mean lengths for each age group are better estimates of those of the population than are the observed sample means. The two standard deviations limits can be estimated about the population means and the sample values are found to be within these limits.

Comparison with previous studies shows that the Clyde fish are smaller and shorter-lived than more northern specimens, though broadly speaking the rate of growth for comparable ages is not so dissimilar.

Laboratory and field observations were made on the food and feeding of the starfish in relation to its role as a predator on oyster beds in the rivers of Essex, particularly in the river Crouch.

Asterias rubens was found most likely to be associated with large numbers of Crepidula, the most serious competitor of the oyster.

Laboratory experiments showed that although Asterias occasionally ate spat and adult oysters, the greater part of its food was made up of organisms which are competitors of the oyster. The smaller sizes of Asterias ate large numbers of barnacles, with occasional spat of oysters and Crepidula. The larger occasionally ate oysters and oyster spat, but almost always exhibited a preference for mussels and, in the absence of these, for Crepidula, and sometimes even for Urosalpinx.

Some observations were made on the method and rate of feeding and distribution of Asterias and Solaster papposus, and certain aspects of the feeding behaviour of the stone crab, Hyas araneus.

It was concluded that Asterias is not such a serious enemy of the oyster as was previously supposed, and that under certain conditions, its presence may be beneficial to oyster culture.

As certain previous authors have observed, T. larynx is a species subject to much variation. Disregard of this has led to the erection of invalid species.

The descriptive characters used by Allman are discussed. In a comparison with material collected in Plymouth Sound these characters are shown to be so variable that used singly they are valueless. In particular, disregard of the stage of development and over-emphasis on size will be very misleading.

The causes of some of this variability are suggested.

Idotea feeds on large food masses. It is potentially an omnivorous scavenger, but each species may have a characteristic diet depending on the availability of food in its particular habitat.

The structure, topography and action of the mouthparts are described: spines on the maxillules and maxillipedes scrape the food material whilst the mandibles actually bite the food; toothed spines on the maxillules and mandibles push the food upwards to the molar processes of the mandibles; debris is brushed forwards between the lobes of the paragnath by setae on the inner endites of the maxillules, maxillae and maxillipedes; and spines on the maxillipedal palp, and on the first leg, comb the mouthparts.

The structure of the foregut resembles that of Asellus and Ligia.

The relation of the feeding mechanism to the functional evolution of the mouthparts of Peracarida as a whole is discussed.

A more complete study of reproductive behaviour is possible where observations can be made on individuals. This is especially so in a population where each individual has a succession of breeding cycles which are not synchronous with those of other individuals. Continuous records of the breeding of individual barnacles is possible in species which have a membranous base. Individuals may be grown on glass slides and the reproductive condition determined by observations through the base.

Reproduction in Elminius modestus takes the form of a succession of breeding cycles or broods, each cycle being initiated by copulation, oviposition and fertilization of the eggs in the mantle cavity. Here the eggs develop, and embryos are eventually liberated through the opercular valves.

The time interval occupied by a brood varies both among individuals and with the season of the year. The time of development of the embryos appears to be a function of temperature alone, but the regeneration of the ovary depends upon the nutrition and food supply. When the ovary regenerates rapidly, as in the period of rising temperature, viz. in spring and early summer, another fertilization follows closely upon liberation, but in autumn and winter the ovary may not mature for some time after liberation, with the result that a large proportion of the population do not contain egg masses. In spring and summer the fecundity is probably limited by the rate of development of the embryos; in autumn and winter by nutrition.

There is a slight tendency for eggs to remain in the mantle cavity for a longer period during the falling temperatures of autumn and winter than at corresponding rising temperatures in spring and summer.