In a collection made with a 2 m stramin ring trawl at 47°03′ N., 5° 47′ W. on 4 July 1956, with 800 fathoms of wire out, I have found a new species of medusa. This specimen is in a comparatively good state of preservation except that the stomach is badly damaged.

The umbrella is hemispherical and the jelly is moderately thick. The form of the stomach cannot be described for certain. Parts of it are to be seen as narrow strips hanging down from the upper ends of three of the radial canals. One of these strips is continued for a short distance along the subumbrella surface towards the summit. It has the form of two short curtains with a space between them which leads into the radial canal. It thus seems quite possible that the stomach is i n fact an open cross with mouth lips extending along each arm as in Staurophora.

The disappearance of mercury from stored sea-water solutions of mercuric chloride has been studied by means of the chloroform-dithizone procedure and by the use of radioactive mercury (203Hg).

When sea water is enriched with nutrients facilitating the growth of bacteria, the rate at which mercury is lost from the solution is markedly increased. On the other hand, when the sea water is treated in various ways which prevent the development of bacteria, the loss of mercury from solution is considerably reduced.

Rates of loss of mercury measured by the chloroform-dithizone procedure and by the use of tracer isotopes are in good agreement only in the early stages of the experiments. Thus, at a time when approximately hah0 the mercury has been lost, titrations with chloroform-dithizone only account for about 50% of the mercury determined by measurements of radioactivity. Further findings have suggested that this discrepancy arises from the fact that a considerable amount of the mercury is taken up by bacteria and converted into a form which is not detectable with chloroform-dithizone.

A study has been made of the toxicities of mercuric chloride, mercuric iodide and methyl-, ethyl-, n-propyl-, n-butyl-, n-amyl-, iso-propyl-, iso-amyl- and phenylmercuric chlorides to larvae of the crustaceans Artemia salina and Elminins modestus. With both species it has been found that all the mercury compounds are more toxic than mercuric chloride, that primary alkylmercuric chlorides are more toxic than the corresponding secondary compounds, and that as the homologous series of primary compounds is ascended, toxicities increase. In addition, it has been found that Elminius is much more readily poisoned than Artemia by each mercury compound, and that differences between the toxicities of the poisons to Elminius are much smaller than corresponding differences observed in experiments with Artemia.

Growth-rings on the shell of the scallop (Pecten maximus) are laid down annually, in spring, and so can be used to determine the age.

Scallops grow from spring to December, and cease growing in winter. The resumption of growth in the spring is marked by the appearance of the annual growth-ring at the edge of the shell.

The first year's growth is of one of two types. A few scallops have shells which show a large first year's growth, 28 mm or more wide, while the great majority have shells which show a small first year's growth, less than 28 mm wide. These two types probably depend on the two principal spawning periods of the scallop, most of the former arising from the spring spawning and most of the latter from the autumn one.

The growth curve of P. maximus is of a type characteristic of lamellibranch shells. The annual growth is greatest in the first two or three years of life, after which it decreases steadily.

Scallops grow more quickly in shallow water than in deeper water.

Possible causes of the annual cessation of growth are discussed.

A paucity of young scallops was noted in the dredge samples, as previous workers have reported. No reason can be given.

Observations have been made of the surface currents off the Northumberland coast over a period of 12 months, using a free-floating buoy. A mean vector current was found, setting 114° at o·i knot. Currents flowed into the quadrant to the right of downwind except when this would have directed them ashore. A relationship is established between wind speed and current speed.

Vitamin A and carotenoids were measured in six species of Penaeidae and seven species of Sergestidae.

Vitamin A was present in at least one sample of all species except Gennadas borealis at concentrations mostly of the same order as previously found in other Decapoda, but usually higher in the Sergestidae than in the Penaeidae.

Carotenoids in the Penaeidae included astaxanthin and its esters, carotenes and xanthophylls, but only astaxanthin or its esters with occasional traces of xanthophylls were found in the Sergestidae.

A method, suitable for routine use, of determining total iron in sea water is described. The water is acidified to about o·13N with hydrochloric acid and is heated for 5 h in an autoclave at 140°C. Iron is determined absorptiometrically with 1:1 phenanthroline after reduction with hydroxylamine hydrochloride.

Tests of the method, collection and storage of samples and the variability of results are described.

Iron contents of water samples from the English Channel and the Bay of Biscay are reported.

The intertidal zonation of the dominant algal species in Beer Bay, south-east Devon, was examined in relation to substratum by means of plane-table maps and transects. The dominance of Ulva lactuca on colonies of the reef-building worms Sabellaria alveolata was noted, but the distributions of Fucus vesiculosus, F. serratus, Gigartina stellata and Enteromorpha spp. showed no correlation with substratum.

The spectral composition of the light of four species of polynoid worms has been measured, viz. Harmothoë longisetis, Gattyana cirrosa, Polynoë scolopendrina and Lagisca extenuata. The method involved the use of coloured spectral filters and two multiplier phototubes. The spectral emission curves of the four species are similar. They are asymmetrical in shape, prolonged towards longer wavelengths, with maxima at about 515 mμ (510–520 mμ.). Values for luminous efficiency are calculated (ratio of luminous flux to radiant flux); for human scotopic vision (λmax at 505 mμ), efficiency is 61%.

In January and March, during the 1955 plaice spawning season, plankton samples were collected with a Heligoland larva net at stations on a grid around a floating radio buoy in the southern North Sea. There was a decided scarcity of suitable food for plaice larvae in the January patch, and this famine was reflected in the deteriorating physical condition of those larvae caught at the transition stage of development, when yolk reserves were becoming exhausted and an adequate external food supply essential. By March, the spring plankton outburst was in full swing. The condition of transitional larvae improved in this good food patch. Feeding started about the mid-yolk phase, mainly on plants. By the time most of the yolk had been resorbed, the appendicularians Oikopleura and Fritillaria had become the principal food items, and remained so throughout pelagic larval life.

The osmotic pressure of the blood of Scrobicularia plana has been measured when the animal is exposed to diluted sea water, and observations made on the behaviour of the animal when exposed to solutions of different osmotic pressure.

The blood osmotic pressure shows no significant difference to that of the external medium except in very low salinities. The external medium with which an animal in its natural habitat comes into equilibrium is represented by the water above the mud rather than the water contained in the mud. Open animals equilibrate to 80% sea water in 4–5 h and to 60% sea water in 5–6 h. The osmotic pressure of the blood of animals that remain closed in dilute media is decreased by as little as 1·5% per hour.

The fishes harbouring parasites of the genus Lernaeocera can be divided, according to the presence or absence of contact with the coastal waters, into ‘inshore’ and ‘offshore’ groups. According to literature, only L. branchialis occurs commonly on hosts in both groups. The difference between this and the remaining species of the genus is explained by the existence of two different species covered by the name L. branchialis. One of these species is parasitic on cod and whiting, the other on haddock. The two species have also different intermediate hosts (flounder and lemon sole respectively) and differ in morphology of the adult male and female and in the mode of attachment to the final host.

Lernaeocera of whiting and cod is distributed mainly in the coastal area, while that from haddock extends over the whole of the North Sea. The former, but not the latter, is present outside the European continental shelf. All these differences lead to the conclusion that the two types represent two different species. The old name is retained for the parasite of cod and whiting. The parasite of haddock is the new species, to which the name Lernaeocera obtusa is given.

In the study of marine diatoms examination of fresh material (or of wet mounts in some suitable preservative such as formalin-sea water) is essential, in addition to ‘permanent’ mounts of ‘cleaned’ frustules, because the violent cleaning process destroys many of the more delicate forms (e.g. the genus Guinardia). Conversely, it is not possible to see the fine details of skeletal structure, upon which the taxonomy of so many diatoms is based, while the organic contents of the cells are still present.

Idotea metallica Bosc occurs occasionally in plankton from waters off the west coast of Britain, but since it does not seem to be a British resident it was excluded from a recent review of the genus Idotea (Naylor, 1955 a). Accounts of the distribution of /. metallica seldom distinguish between occasional records and resident breeding localities, and this note attempts to explain its occasional occurrence in Britain.

In the 4th to 8th thoracic segments of decapod Crustacea, at the bases of the peraeopods, sensory organs of various kinds have been found. They have been observed in Homarus vulgaris, Astacus astacus, Palinurus vulgaris, Eupagurusbemhardus, Carcinus maenas, Maia squinadoand described in greater detail for Homarus, Carcinus and Maia.

In all species examined there is in each peraeopod a proprioceptor consisting of a thin muscle with various nerve elements which extends from a point of the endophragmal skeleton situated near the ventral ganglia to the anteroventral part of the coxa. In the 4th to 7th thoracic segments of Homarus, in the 4th to 8th of Palinurus and Astacus, and in the 4th of the Brachyura, the receptor muscle is proximally attached to the tip of a chitinous projection of the endophragmal skeleton for which the term ‘receptor rod’ is proposed. In other instances it originates on the plate of the endosternite.

The nerve components of this ‘muscular receptor’ are of two sorts: (1) motor nerves spreading their branches over the whole length of the muscle, and (2) processes of the sensory neurons distributing their ramifications on the connective tissue associated with the muscle at its proximal end. The arrangement of the sensory elements is different in various species, but they all exhibit one feature, unusual in invertebrates, viz. their cell-bodies are situated within the central nervous system and not outside it.

The spectral composition of the light of Chaetopterus variopedatus has been measured by means of spectral niters and multiplier phototube. Spectral emission extends from about 405 to 605 mμ, with a maximum at about 465 mμ. The spectral curve of Chaetopterus light is compared with a human visibility curve (scotopic vision), a visibility curve for Limulus, and an absorption curve for fish visual purple. Luminous efficiencies, based on these curves, are calculated.

Cell ovoid to almost sphaeroidal in face view of right or left valve, lenticular to almost sphaeroidal in view showing junction of valves, in both views flagellar pole flattened, length (10) 14–17 (22), breadth (9) 11–15 (20), thickness (5) 6–8 (18) μ. Two valves of cellulose, each with a striated band at margin, band wider in larger cells, striations about 0–5 μ apart, remainder of valve surface with poroids, apparently in rows, 0–25μ apart, poroids 0.2–0.2 μ. diameter; right valve with shallow indentation, about 2 μ wide, at flagellar pole, usually lying to left of centre line; left valve with small projecting flange, about 2 μ wide, bearing flagellar pores and fitting into and over indentation on right valve; the two flagellar pores of unequal size, in apical view larger nearly triangular, smaller circular, in left valve view smaller pore to left of larger.

Measurements were made on the intact retinae dissected from freshly caught deep-sea fish. The unbleached retinae of such fish are not rose-pink like the retinae of most coastal fish or purple like the retinae of most freshwater fish, but are golden in colour.

The golden colours are of photosensitive pigments which give retinal absorption curves similar in shape to frog's rhodopsin, but with maxima of absorption displaced on the average about 15 mμ. towards the blue end of the spectrum. The names ‘chrysopsins’ or visual golds are suggested for this group of pigments.

The density of such photosensitive pigments is often very high. Retinal density changes on bleaching of more than 1.0 has been found for several deepsea fish. These probably correspond to absolute retinal densities of pigment of about 1.3, i.e. the absorption of 95% of blue-green light striking the retina.

The conger and silver freshwater eels have retinae containing similar golden-coloured pigments. These eels begin their lives in the deep ocean and return there when mature to spawn.

The significance of this type of photosensitive pigment in the vision of deep-sea fish is discussed, and an estimate is made of the depths at which deepsea fish will see daylight.

The distribution and ecology of subspp. anceps and edentatus of F. distichus L. emend. Powell (1957) in Britain and Ireland is described in detail, based on recent ecological surveys and critical examination of all past records.

F. distichus anceps is a small form confined to certain very exposed coasts in the north and west of Scotland and Ireland, where it reaches the southern limit of its geographical range. This plant may be a relict form in Britain, existing now only under an extraordinarily narrow range of rigorous habitat conditions; it is not thought to be actively extending its range southwards at the present time. The ecology of subsp. anceps is considered principally in relation to that of other reduced fucoids found on exposed British shores, viz. F. spiralis f. nana and F. vesiculosus f. linearis; all three forms are illustrated by photographs and means of distinguishing them are described. The lifespan of subsp. ancepsis thought to be 2 to 3 years at some Irish sites, but may be longer at some of the Scottish sites.