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.

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.

The tidal rhythm of migration of the mud-fiat diatom community is a curtailed diurnal rhythm. Evidence is given of the similarity of these two oscillations in the laboratory and in the natural conditions of the estuary. However, the interference of the diurnal rhythm by water or stirring results only in one repeated rhythm on the following day; thereafter the migrations revert to a day-length-induced synchronization.

There are two main types of muscle fibre in the dogfish myotome. Slow fibres make upabout 18 % of the mass of the myotome, the remainder consisting of fastfibres. The slow and fast fibres have a different pattern of innervation, and differ in such respects as their fat and glycogen contents, and in abundance of mitochondria. The two typesof fibre show different responses to depolarizing agents.

Extracellular recordings from the myotomal muscle taken during the swimming of spinal fish show that only slow muscle fibres are active when the fish swims slowly, whereas during vigorous movements, the fast fibres are active. Although both types of fibre contain glycogen, the fast fibres contain only about 50–60 % ofthe amount found in the slow fibres. After a period of vigorous movement, the glycogen levels in the fast fibres fall markedly, whilst those in the slow fibres donot change. The slow fibres contain around 4–5 times the amount of fat found in thefast fibres; after long periods of sustained slow swimming, the fat levels inthe slow fibres fall, and there also may be a slight decrease in the glycogen levels in the slow fibres. Long periods of slow swimming do not alter the glycogen levels found in the fast fibres.

In simple choice experiments Protodrilus symbioticus Giard, an interstitial archiannelid, was shown to prefer the sand from its habitat in the natural state to the same sand altered by various physical or chemical treatments. The attractiveness of a sand was measured as the ratio of the number of Protodrilus entering the experimentally treated sand to the number entering the natural sand in simple or multiple choice experiments.

The attractiveness of natural sand to P. symbioticus could be destroyed almost completely by acid cleaning, by heating in water above 50° C or by drying at any temperature.

Treating attractive sand with formalin or cetyltrimethylammonium bromide rendered it about half as attractive as before treatment. Heating natural sand in water to 40°C and keeping it in fresh water for 18 h had no effect on the attractiveness. Sands that have been made unattractive by acid cleaning or drying can be restored to an attractive state by soaking in sea water. Typically acidcleaned sands recovered up to half and dried sands almost the whole of the attractiveness.

Inoculation of naturally occurring sand bacteria to highly unattractive acid-cleaned sand restores the attractiveness completely. Autoclaved sand to which a culture of Phaeodactylum had been added was preferred to sand treated with cultures of Dunaniella and Chlorella. An ordinary culture of Phaeodactylum contaminated by bacteria restored the attractiveness to autoclaved sands more effectively than a bacteria-free culture.

Sands restored by inocula of natural sand bacteria, soil bacteria and Pseudomonas sp. were preferred to those treated with Corynebacterium erythogenes, Flavobacterium sp. and Serratia marinorubra and these were preferred to control sands kept in sterile sea water.

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 structure of the tentacle in two species of Pogonophora (of the genera Nereilinum and Oligobrachia) has been investigated by light- and electron-microscopy. The fine structure of the pinnules, epidermal cells and mucous cells is described. The surface membrane of the epidermal cells and the pinnules forms an elaborate system of microvilli which traverse the cuticle and often extend up to the surface particles.

The classical problem of decapod egg-membrane formation and egg attachment was studied in Carcinus maenas, Homarus vulgaris, Nephrops norvegicus and Astacus pallipes. It was found that no fundamental difference existed in the membranes of the above species, and that some of the current views on the physiological processes involved were incorrect. The present study indicated that no externally deposited membranes have been formed around the egg at any stage. The outer-most membrane really consists of three layers which are histochemically distinct from one another and cannot be equated with epicuticle. The outermost layer (layer 1) of this membrane is derived from the vitslline membrane, the second layer (layer 2) is formed through solidification of a fluid exuded from the egg at spawning, and the third layer (layer 3) is formed by highly PAS-positive substance from the egg. It is suggested that the formation of this ‘trichromatic membrane’ is initiated by fertilization.

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 metabolic or respiratory rate, measured as the aerobic oxygen uptake, of the limpets Patella vulgata L. and P. aspera Lamarck was determined over a range of temperatures in January and in July. In order to determine the effects upon metabolism of adaptation to habitat, P. vulgata living at high shore levels were compared with those living at low shore levels.

The respiratory rate is proportional to the power –0·3042 of the fresh body weight and the relationship is not affected by temperature or season, and is the same for both species.

There is very little difference in the rates of respiration of equal weight individuals of P. aspera and either group of P. vulgata in January. In July the respiratory rate of low-level P. vulgata and of P. aspera is higher than in January whilst that of the high-level P. vulgata is little changed.

The Q10 of respiration had a low value between the temperatures of 15–20° C in both species, and this is thought to represent a hitherto unrecognized form of acclimation to maintain metabolic constancy over the mean environmental temperature range. In P. vulgata low values of Q10 were correlated with high environmental temperatures. Lower Q10's were recorded in July than in January and, in addition, limpets which were adapted to the elevated temperature of high shore levels in July had lower Q10's than the limpets from low shore levels. This apparent acclimation of Q10 was not observed in P. aspera.

The significance of the differences in metabolic rate and in Q10 are discussed in relation to acclimation and its importance in the ecological distribution of the two species.

An earlier paper (Holme, 1961) described the bottom fauna off the south coast of England, as sampled by a modified anchor-dredge. Sampling was later extended to cover the whole English Channel, a further 144 stations being worked, making 311 in all. This paper describes the results of the later survey which, as previously, was concerned mainly with molluscs and echinoderms. Distribution charts for the majority of species identified are given, in which are incorporated the results of both surveys.

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.

A 250 ml. chemostat has been used to measure the parameters of vitamin B requirement in the chrysomonad Monochrysis lutheri.

The yield constant was ca. 0·25 × 10 cells/μμg., i.e. one-third of the figure previously measured in batch cultures.

The saturation constant lay between 2 and 6 μμ/ml., i.e. at least twenty times the figure indicated by previous batch culture measurements.

Internal inconsistencies in the chemostat's operation indicate the presence of factors not accounted for by theory.

It is argued that only factors analogous to the release of protein-bound vitamin into the medium could in principle account for all the discrepancies.

Nannochloris oculata Droop, an obligate phototroph, has no absolute nutritional requirement for any organic compounds. However, no growth takes place in neutral media lacking base, due to the lengthening of the initial lag phase. Weak acids shorten the lag even though pH has not been altered. The lag is interpreted as the time taken for the cells to excrete sufficient weak anions to lift the carbon dioxide in solution to the minimum required for growth. Glycollate excretion is discussedin the light of this interpretation.

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.

Thirty-nine strains of (mainly) supra-littoral algae were tested for their ability to utilize glycollic acid for chemotrophic and phototrophic growth at the' natural' pH of 8.c. In no instance was there convincing evidence that glycollate either supported growth in the dark or enhanced the growth rate in the light in the presence of carbon dioxide, although acetate performed one or both these functions in a number of the strains. It was concluded that glycollic acid was unlikely to serve as a significant carbon substrate in neutral or slightly alkaline habitats.

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.

A survey has been made of reflecting layers in the integument of selected fishes, including silvery sea lamprey and various silvery and partially translucent teleosts. Lamprey and juvenile rockling have only a stratum argenteum. Other silvery teleosts have a layer of oriented reflecting platelets lying outside the stratum argenteum; these lie more or less parallel to the vertical to the surface of the water.In dace, herring, and salmon parr the platelets on the upper flanks are tipped slightly upwards; but in some pelagic fishes, e.g. the mackerel and gar-fish, the platelets here are tipped downwards. Smelt, sand smelt, half-beaks, found in shallow or coastal waters, are partially translucent, partially silvery. The implications of these arrangements of reflecting layers are discussed. Both in clear oceanic waters, away from the surface, and in shallow or turbid rivers or ponds, light is distributed almost symmetrically about the vertical to the surface, and the greatest intensity is directed downwards. Under these conditions the reflecting layers diminish thevisibility of the fish from most fields of view because they reflect light approximately equal to the background light against which the fish is seen. On the lower flanks, when the surface is sloping, the reflected light tends to be spread and to beless intense than the incident light. Thin fishes, dark above with vertically reflecting sides, are effectively camouflaged except for the ventral extremity. The lower flanks of tapering or rounded fishes are well camouflaged by reflexion from below and behind because the platelets slope inwards towards the tail, and the projected area of incidence relative to reflexion is thereby increased.