The life-histories of the erycinaceans Montacuta substriata and M. ferruginosa were investigated with special reference to the initiation of their ‘commensal’ associations. The planktotrophic larvae are released in summer as veligers after incubation within the adults, and they may spend several months in the plankton before settlement and metamorphosis. Larvae of both species, isolated from the Plymouth plankton, were reared to post-larval stages that were comparable with spat found associated with spatangoids. Some corrections are made of the identifications of planktonic larvae, of these and other Erycinacea, by previous authors. Experiments showed that, apart from being more active, the responses of walking post-larvae are similar to those I have described previously with adults. It is considered that the reactions operate, in an integrated manner similar to the adults, in initiating their associations with spatangoids; the behaviour of the adults in maintaining and re-establishing their associations would thus represent a retention of larval faculties. Possible reasons for the restriction of M. substriata to superficial burrowers and the less specific occurrences of small M. ferruginosa amongst spatangoids—including both deep and shallow-burrowing species—are discussed.

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.

Experiments on yolk utilization were done with developing herring eggs and larvae from races spawning in the Clyde, North Sea, Atlantic and Baltic. The range of mean dry weight of unfertilized eggs varied from o·126 to o·366 mg in the different races.

The ultra-structure of the epidermis of herring larvae is described. It is composed of two cell layers; the outer layer contains mitochondria, vesicles and a practically continuous layer having a dense 'fibrous' appearance. The cell border in contact with the sea water is thrown into an irregular arrangement of ridges and pits. The inner cell layer is usually thicker than the outer layer and lacks the continuous dense layer. No differences could be found in the structure or thickness of the epidermal cells of larvae reared in salinities of 5, 17·5, 35 and 50 ‰

Observations were made on the feeding and respiration of the common small copepods in the Clyde sea-area, using cultures labelled with P for feeding experiments and the Winkler method of oxygen determination for respiration measurements.

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.

It has not been known with certainty that the haddock produces underwater sounds of biological significance, though various authors have suggested the possibility.

Descriptions are given of sounds (grunts and rasp-like noises) produced in particular behavioural contexts by haddock maintained in tanks, and of sounds recorded at sea and attributed to haddock. Oscillograms and a spectrogram of these sounds are given. It is suggested that the sounds are involved in aggression and self-defence.

The sound-producing mechanism is described.

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.

The development of an ellobiopsid parasite,Thalassomyces fagei (Boschma), within the cephalothorax of an euphausiid,Thysanoessa raschi (M. Sars), is described for the first time. The tissues of the young stages of the parasite have no intimate connexions with those of the host but become fused with them when the trophomeres begin to differentiate into a series of gonomeres. The parasites are found inT. raschi but have not been found in recent years in the associated population of the euphausiid,Meganyctiphanes norvegica (M. Sars), although it was recorded in one specimen of this species in 1925. The older stages of this parasite only occur inT. raschi in the Clyde during the period March-June but they have been recorded in the same species and other species of Northern Atlantic euphausiids in other sea areas later in the year. No fresh evidence has been found to decide whether these parasites have dinoflagellate, rhizopod, or fungal affinities.

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 eggs of two common cirripedes, Balanus balanoides and B. balanus, have been analysed at different stages of development for their lipid content.

Triglyceride and phospholipid are the main lipid components; small amounts of free fatty acids, lipochromes, sterols, and some very non-polar material (possibly hydrocarbon) are also present.

Lecithin followed by phosphatidyl ethanolamine make up a large proportion of the phospholipid fraction.

The fatty-acid spectrum is similar to that of other marine animals being rich in unsaturated fatty acids of which eicosapentaenoic (20:5) and docosahexaenoic (22:6) predominate.

Triglyceride is lost during development.

Initially some lecithin and phosphatidyl ethanolamine are lost during development, but they accumulate in the late stages.

Cardiolipin shows a marked increase in quantity during the late stages; this is presumably associated with increased cellular differentiation.

There is a tendency for all the components to approach the values for the adult bodies—taken when lipid reserves are minimal—as the embryos develop.

Consideration has been given to the cell diameters of twenty-four samples of Rhizosolenia styliformis var.oceanica from a wide range of latitude together with material from eleven other collections already briefly recorded in Part II of this paper.

It was found that the cells of the smallest diameter occurred in high latitudesand that the average values were greater at lower latitudes.

More auxospore generations were present simultaneously in higher latitudes. An interpretation of these observations is that the prevalence of smaller cell diameters and the simultaneous presence of more auxospore generations in high latitudes could be due to relatively lighter grazing by herbivorous zooplankton in these regions.

Measurements of a few samples of a form of Rhizosolenia styliformis (Bright-well) which I called var. oceanica have been published earlier (Wimpenny, 1946), and auxospore formation was recorded from the Faroe-Shetland area. Since that time, owing to the kindness of the late Dr Vedel Taning, I have been able to see sixteen samples taken in the North Atlantic by the Danish research ship 'Dana' in1948. Mr J. Corlett of the Fisheries Laboratory, Lowestoft, has also been good enough to have made available to me three collections containing this variety from the Weather Ships 'Jig' and 'Item' in 1950 and two from the west ofBear Island in 1952. Finally, I have to add two samples of 33 and 50 specimens fromthe northern North Sea area made available to me many years ago by the late Miss Ogilvie and another sample from which I have been able to measure 100 specimens givenme by Dr James Fraser (E 34, 1934).

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.

Data are presented on the lipid composition of Balanus balanus spermatozoa.

Lecithin is the major lipid and little plasmalogen is present.

The results are discussed in relation to what is known of other spermatozoa, both vertebrate and invertebrate.

Some data on the inorganic and organic constituents of Balanus balanus seminal plasma have been given by Barnes (1962 a, 1963); lipids were shown to be present in the plasma and are a well-known constituent of the spermatozoa of other animals (Mann, 1964). In view of the relatively small amount of data on the detailed phospholipid composition of invertebrate spermatozoa the opportunity was taken during the investigation reported in the previous paper (Dawson & Barnes, 1966) to examine the spermatozoa of Balanus balanus. The results are, however, best presented and discussed separately. The results are given in Table 1.

Cod (Gadus morhua L.) from the Arcto-Norwegian stock that spawns off northern Norway were caught at various times during the course of their gonadal maturation cycle, and plasma samples were collected for the determination of vitamin A compounds and lipids.

The main changes found concerned vitamin A aldehyde, which increased from a resting level of2μg/100 ml. plasma for adult females caught in September to 10 μ/100 ml. in ripe females caught in January-March approaching their spawning grounds; by contrast little change was observed in the males. In the fish of both sexes caught in September, just prior to the onset of maturation, dehydroretinal formed about 38 % of the total aldehyde, but in the plasma of ripe females the proportion was only 16 %. In both sexes there was a fairly steady decline in the levels of vitamin A esters and alcohol in the plasma during the winter. Similarly, the concentration of plasma lipids fell during the winter in the male cod, but in the adult females, during the period of ovarian maturation, the concentration of lipids increased and was maintained at about 0·5 g/100 ml. higher than in the males; in spent fish the concentration of lipids fell to the same low levels in both sexes.

It was considered that the changes in vitamin A aldehyde, and also of blood lipid, in the females were directly linked with sexual maturation, these compounds being transported to the developing eggs in the ovary. On the other hand, the general decline of vitamin A esters and alcohol in both sexes, and of lipids in the males, was probably due to the obligatory winter starvation which occurs in this stock.

The definition of Ectocarpus by Hamel (1931–39) is accepted and his division of the genus into two species complexes, E. fasciculati and E. siliculosi, vindicated. Observations on the E. fasciculatus complex show that its component taxa rep-resent various stages in thallus growth and elaboration, while the subspecific taxa of E. siliculosus are determined primarily by size and shape of plurilocular sporangia. Both species are shown to undergo a streblonemoid phase in their early development. Field observations are confirmed by following the growth of both species in culture. The habitat and host range of both species is found to be wide.

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.

Detailed sampling of the bottom water of Christchurch Harbour, England, was undertaken in conjunction with a study of the living and dead foraminiferids (to be described later). The Harbour is a shallow estuary with an unusual tidal regime of four high tides daily. During the winter the flow of fresh water from the rivers prevents sea water from entering much of the estuary. During the spring, summer and autumn, when drier conditions prevail on land, the sea enters the estuary as a salt wedge and there is pronounced salinity stratification. In addition to determinations of chlorinity, pH, dissolved oxygen and temperature, analyses of calcium were made during the spring, and of calcium and magnesium in the summer. It was found that calcium was preferentially removed from the bottom water, thus upsetting the calcium-chlorinity ratio. The cause of the calcium removal is thought to be biological activity. Magnesium was not affected by this process. A discussion of the results is presented and it is suggested that biological removal of calcium from the bottom water is particularly well developed in Christchurch Harbour owing to the extensive areas of shoal water favouring biological activity. Estuaries of this type may not be very common.

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.

An account is given of the distribution of certain polysaccharides, lipids and proteins in the tissues of Siboglinum atlanticum, a uni-tentaculate pogonophore collected from depths of 1300–1500 m on the continental slope. The histology of the various glands and cells is described, and the structure and histochemistry of the tentacle compared with that of three multitentaculate species of pogonophores collected from similar habitats.

Esterases hydrolysing a naphthyl acetate and o-acetyl-bromoindoxyl are found in most tissues of Siboglinum after formalin fixation. An eserine-sensitive esterase was present in the dorsal ciliated band, mostly close to the bases of the cilia. An organophosphorus-resistant esterase was widely distributed as scattered particles in the subcuticular region of the epidermis of the tentacle and anterior end. The other tissues, including the epidermal glands, blood vessels, muscles and peritoneum, contained a simple B-esterase which was closely associated with lipid globules; the nerve fibre B-esterase was not associated with lipid and its apparent sensitivity to copper illustrates one aspect of the difficulty of applying mammalian esterase subdivisions to invertebrates. Lipids form the main food reserve, and appear to have a dominant role in the metabolism.

Pogonophores do not possess a gut at any stage in their life, and must take up food through the epidermis, whether or not it is first digested. The epidermal glands do not appear to have any digestive function. The multicellular pyriform glands secrete fibres of chitin and acid mucopolysaccharide, and produce the major part of the tube in which the animal lives. The unicellular glands are of several types, but most of them, apart from some simple mucous glands, appear to take part in tube formation, secreting mucopolysaccharides or mucopolysaccharides and protein.