The length, weight, calorific value and organic matter content of Calanus finmarchicus, Stage V, males and females, were measured in monthly samples taken from April 1962 to June 1963.

There is considerable variation throughout the year and all stages had their maxima of weight and calorific value in spring, 1962, and winter 1962–63.

The calorific value and weight are closely correlated so that, knowing the dry weight, the calorific value can be calculated from it. The correlation is closest in Stage V and, for these, only the dry weight need be known. Since the relation-ship is slightly different for males and females the sex of the adult must be known as well as the dry weight; curves showing these relationships are given.

The calorific value obtained from organic-matter analysis at times deviates widely from the values obtained in direct bomb calorimetry, and it is concluded that in the method used not all the fat is accounted for.

In weight, calorific value, and organic matter, but not in length, Stage V for a good part of the year show higher figures than adults.

In comparing the weights with those of other years and other places, the annual pattern is found to vary considerably. The spring maximum seems to occur every year, but there may be either a maximum or a minimum in autumn and winter.

Arsenate was found to interfere with both of Murphy & Riley's methods of estimating phosphate in sea water. The magnitude of interference showed day-to-day variations.

Five methods of estimating dissolved inorganic phosphate in sea water were compared in the northern North Atlantic. Differences observed between the methods were related to those found in similar earlier investigations in inshore waters by Jones & Spencer.

The sampling of a discrete unfished population of escallops at Holyhead by diving showed that there was no influx into the area of escallops at any age or size, other than by spat settlement. The success or otherwise of the spat settlement, which was very variable, determined the age- and size-distribution of the population. Evidence is adduced that normal dredge sampling gear is very selective or, if it is made unselective, becomes too laborious to use because of the low densities of escallops. In a commercially fished population the failure to catch the smaller escallops by the sampling dredges, combined with the fishing off of the larger ones, makes the age-distribution of the population appear always to be dominated by the 2- or 3-year-old escallops. The great variability of the success of year-classes is masked by this sampling selection combined with the effects of commercial fishing.

Field and laboratory observations were made of the erycinacean bivalves Montacuta substriata and M. ferruginosa, which are usually considered as ‘commensals’, respectively, with the burrowing spatangoids Spatangus purpureus and Echinocardium cordatum. These species were obtained mainly from the Plymouth area, where M. substriata was also found with E. flavescens and E. pennatifidum, and also very occasionally with E. cordatum. Similarly, M. ferruginosa was also found with 5. purpureus, E. flavescens and E. pennatifidum. This indicated that the associations are not as specific as had been thought.

The behaviour involved in the maintenance of the ‘commensal’ associations of Montacuta substriata and M. ferruginosa with spatangoids was investigated experimentally.

Both species are highly mobile when isolated from the ‘host’, and this activity was recorded through their mucous trails on glass plates, and photographically with a repetitive electronic flash system. Their responses were analysed mainly in a trough apparatus with a slow flow of water. The behaviour was resolved into responses to factors normally present in their environment. These included both gravity and water currents and a chemical influence from the ‘host’ spatangoid. M. substriata showed a marked negative geotaxis, while M. ferruginosa showed a similar response but of opposite sign. Pedal activity was stimulated as a kinesis to an unknown chemical ‘attractant’ from the urchin. The bivalves showed no specificity in this response since it was shown by both species to any of the spatangoids tested, regardless of the urchin species from which they were taken.

A new species of enchytraeid worm, Lumbricillus christenseni, is described and compared with some closely related members of the genus Lumbricillus.

Twelve other species of enchytraeid, recorded in the British Isles for the first time, are listed.

The habitats and localities in which these new records have been found in North Wales and Europe are also listed.

A revised check-list of the British Enchytraeidae is given.

Following the publication (Nielsen & Christensen, 1959) of a critical revision of the taxonomy of European enchytraeids, which resolved much of the confusion in the existing literature, the task of identifying the members of this family has been made much easier. Between 1961 and 1964, during an investigation of the littoral Enchytraeidae of the coasts of Anglesey and the Menai Straits, twelve species of enchytraeid new to the British Isles and one species new to science were identified. The new species, a member of the genus Lumbricillus Ørsted 1844, is hereby named Lumbricillus christenseni, after Dr Bent Christensen of the University Zoological Museum, Copenhagen, in recognition of his contribution to our knowledge of enchytraeid taxonomy.

Lumbricillus christenseni sp.nov.

Location and habitat

This worm has been found in only one location, namely, Porth Eilian, a small bay at the north-east corner of the island of Anglesey, North Wales. The worm was most common at about high-water mark of the neap tide, in a mixture of sand and pebbles with a sparse covering of undecayed weed. The specimens examined were all taken within 5 cm of the surface. There was a large proportion of mature specimens at the time of collection, that is, late spring and early summer of 1964.

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.

Starch gel electrophoresis of extracts of Siboglinum atlanticum showed that all five individuals tested have two acidic haemoglobin components and a strong α-naphthyl acetate esterase. There was individual variation in the position of the esterase. Low levels of amylase activity were found in the extracts but no trace of dehydrogenases for such important substrates as glucose-6-phosphate, lactate, malate, and glutamate could be revealed by standard histochemical methods as applied to zone electrophoresis. The high level of haemoglobin and the protein peculiarities of the Pogonophora are discussed in relation to experiments on respiration. It is concluded that Siboglinum haemoglobin functions at very low oxygen partial pressures and that the high level of haemoglobin dissolved in the blood plasma of pogonophores does not reflect a high level of oxygen consumption or activity. The meagre biochemical data at present available on the Pogonophora do not favour relationship of this phylum to the echinodtrm-chordate line any more than to the annelids or other invertebrate phyla.

INTRODUCTION

Largely as a result of studies by A. V. Ivanov, the phylum Pogonophora has become recognized by zoologists in the past decade (reviewed by Hyman, 1959, esp. pp. 208–27; Ivanov, 1963; E. C. Southward, 1963). Pogonophores are small, extremely vermiform animals, living in tubes partly im-bedded in mud or muddy sand; while in some areas they are sufficiently abundant to dominate the benthic fauna, their occurrence at great depths has made living pogonophores very difficult to obtain.

Two especially interesting problems associated with this newly recognized phylum are:(a) Pogonophora are the only group of free-living Metazoa without a gut at any stage in their development, and thus, the method of feeding and type of metabolism has been the subject of considerable speculation; (b) Pogonophora possess a few characteristics—e.g. a ventral heart and dorsal nerve cord—suggestive of the echinoderm-chordate line of evolution.

Filtration rates for Phallusia were computed from the rate of clearance of sus-pensions of colloidal graphite and of the flagellate Isochrysis. Rates varied from 825 ml./h to 5100 ml./h for animals between 8 and 128 g wet weight (40–336 ml./h/g wet weight; 88–570 ml./h/mg nitrogen). The greater part of this current is ciliary; less than 2 % is accounted for by squirting. Squirting thus plays but a minor role in maintaining the feeding current. Its probable function is perhaps more comparable with the expulsion of pseudofaeces in filter-feeding molluscs.

The hitherto unknown hydroid of the anthomedusa Bougainvillia principis has been found in the Firth of Clyde, 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, and its seasonal occurrence is described.

The historical development of our knowledge of B. principis and of B. superciliaris, which have been confused, is discussed. The hydroid and the young medusae of B. principis are shown to be identical with those described by Hartlaub and attributed by him to B. superciliaris.

Several doubtful species of Bougainvillia medusae described from British waters are considered and are identified with accepted species. Medusa ocilia and M. duodecilia are probably synonymous with Bougainvillia pyramidata and B. principis respectively; and B. nigritella is identified with B. muscoides, B. simplex with B. principis, B. dinema with B. britannica., and B. charcoti with Nemopsis crucifera, itself a probable synonym of N. bachei. The medusa B. alderi is a probable synonym of B. ramosa.

The hydroids and the medusae of the British species of Bougainvillia are reviewed and compared; and records of B. superciliaris and B. macloviana are given.

The component acids of the fats of the following marine algae have been investigated by gas-liquid chromatography:Rhodymenia palmata, Laurencia pinnatifida, Laminaria digitata, L. saccharina, Fucus vesiculosus, F. serratus, Pelvetia canaliculata, Ascophyllum nodosum. The principal saturated acids are palmitic and myristic acids, some contain ca. 2–5% of stearic acid; traces of C8 and C10 saturated acids are present, but C12 (and in all but one) C 20saturated acids are absent. The major unsaturated acids are octadecenoic and octadecadienoic acids (probably oleic and linoleic acids), but some species also contain appreciable amounts (up to 12%) of hexadecenoic acid. All the oils contain significant amounts of an eicosatetraenoic acid (probably arachidonic acid) and in some eicosatrienoic and/or eicosapentaenoic acids are also present in small quantities. Two acids of unknown constitution (possibly branched chain acids) are also present in minor amounts. No C22 unsaturated acids could be detected.

INTRODUCTION

Very little is known about the component fatty acids of marine algae. Lovern (1936) examined the fatty acids from the fats of Fucus vesiculosus, Laminaria digitata and Rhodymenia palmata using lead salt crystallization and fractional distillation techniques (Table 2). With these methods, however, it was not possible to separate individual unsaturated acids having the same number of carbon atoms from one another. The mean unsaturation values of these fractions were therefore evaluated from their iodine values and expressed as the number of hydrogen atoms necessary to convert the fraction to the corresponding fully saturated state; thus ( — 4–0H) indicates an average unsaturation corresponding with two double bonds.

During the last 30 years the fecundity of the plaice, Pleuronectes platessa L., has been widely studied over its complete geographical range. In this paper all this previous work is brought together and a distinct pattern (with two exceptions) emerges. The fecundity is lowest in the Southern Bight of the North Sea, and radiating from there in all directions the fecundity increases, while in Faxa Bay (Iceland) and in the Barents Sea it is lower again. The possible factors producing this pattern are examined in detail and it is concluded that the amount of food available, which in turn is related to population density, is the most important. Only in Trondheim Fjord and in the Baltic is the fecundity so different that it is necessary to postulate racially distinct populations. Finally the importance of fecundity variations in natural population regulation is stressed.

A new species, Navicula avonensis, is described, living on the estuarine sediment of the River Avon at Bristol. It has an extremely hyaline theca and can be tentatively assigned to the section Naviculae subtilissimae.

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.