Since the advent of nuclear fission, considerable interest has been aroused in the biological fate of strontium, as two isotopes of this element are among the longer-lived fission products of uranium. Strontium 90, in particular, constitutes the major hazard in old fission products because it is readily taken up by all kinds of plants and may then be concentrated in the bones of animals feeding on the plants. Strontium 90 contamination may be derived from fall-out from atomic explosions or from uncontrolled disposal of fission products. The oceans should receive more than twice as much Strontium 90 from fall-out as the continents because 70% of the surface area of the globe is covered by sea. The oceans are also used, though to a very limited extent at present, for the disposal of fission products from reactor wastes. Hence it is obviously important to study the behaviour of strontium in marine organisms in order to evaluate the health hazard caused by controlled or uncontrolled radioactive contamination of sea water. Barium has only relatively short-lived fission-product isotopes, but can readily be studied at the same time as strontium because of its similar chemistry.

The summer of 1954 will long be remembered for lack of sunshine, excess rain and frequent high winds over England and Wales. In the south-west of the region the winds from June onwards until the end of the year were predominantly westerly, often reaching gale force, and the total run of the winds was often above average. During the last week of July there were persistent westerly winds from well out in the Atlantic, often strong and reaching gale force at times, particularly on the 27th and 28th. During the last 4 days the winds were generally from the north-west at Scilly and in southern Ireland. They were variable in strength and direction early during the first week in August, but occasionally blew freshly from the south-west. On the 7th it was often blowing strongly from the west, a gust of 50 knots being recorded at Scilly. It was during this first week in August that the first few specimens of Ianthina janthina (Linnaeus) came ashore, heralding the most extensive strandings of this species on British shores for very many years.

The quantitative study of phytoplankton production may be pursued in many ways, but these ways can be divided into two general methods of approach. There is, first, the direct estimation of a production rate for a particular sample of the population; for example, the light-dark bottle technique for measuring oxygen production (Gaarder & Gran, 1927; Riley, 1939) and the new 14C technique (Steeman Nielsen, 1952). These estimates are made under conditions which must be, to some extent, artificial. Secondly, there is the direct estimation of relevant variables in the sea (phosphate, oxygen, chlorophyll concentration, etc.) from which production is calculated on the basis of hypotheses about the behaviour of phytoplankton. These hypotheses are, of necessity, simplifications of a mass of laboratory experiments and of previous field work. Riley, Stommel & Bumpus (1949) give a full account of this approach and of the difficulties involved in it.

During the autumn of 1954 plankton samples were taken in the northern Irish Sea and the North Channel from R.V. Clupea (Scottish Home Department) as part of a larger survey of the distribution of herring larvae. At the same period similar samples were taken in the central Irish Sea from R. V. William Herdman (Marine Biological Station, Port Erin). The present paper concerns the distribution, as shown by both sets of samples, of a few selected species.

I am indebted to all those on both vessels who assisted in taking the samples and to the Marine Laboratory, Aberdeen, for lending me for analysis the samples taken from R.V. Clupea.

A fishery has developed in recent years in this country for certain hydroids collectively termed ‘white weed’. The hydroids, particularly Sertularia and, more recently, Hydrallmania, are raked up from the sea-bed, processed, dyed and used, largely in the United States of America, for decorative purposes. Fishing for white weed is not new, for it was practised in Germany between the wars. German scientists, notably von Reitzenstein (1913), Pax (1928), and Thiel (1938), examined various aspects of the fishery, and of biology of the hydroids concerned.

The sudden appearance of Akera bullata in the static water tanks of H.M. Dockyard, Devonport, provided specimens for the investigation of pigments. Morton & Holme (1955) have given an account of certain aspects of the biology of this interesting tectibranch mollusc.

The two new species, Gymnodinium vitiligo and G. veneficum, which are described below, are both small and highly motile, and in other respects very similar. The greatest difference between them is physiological, as G. vitiligo is harmless, whereas G. veneficum produces a very powerful toxin which is lethal to fish. There are also small morphological differences which are visible when the organisms are in culture, confirming the existence of two separate species.

Sex phenomena in molluscs have been widely investigated, and the relevant literature on the subject has been reviewed by Coe (1943,1944). Coe recognizes ambisexuality (monoecism, hermaphroditism) and unisexuality (dioecism, gonochorism) and further subdivides ambisexuality into functional ambisexuality (functional hermaphroditism), consecutive sexuality, rhythmical consecutive sexuality and alternative sexuality. Of these, functional hermaphroditism is of widespread occurrence: it is encountered in all the main groups, with the exception of scaphopods and cephalopods. Of the more than 20,000 species of living gastropods approximately half are functional hermaphrodites when fully adult (Coe, 1944). Limpets of the genus Patella are unisexual, though there is evidence that sex change may occur in some of the species (Orton, 1920, 1928, in Patella vulgata; Bacci, 1947, in P. coeruled). Little is known with certainty of the mechanism of sex-determination in these animals, but sexuality appears to be labile since it seems that more than 90% of individuals of P. vulgata change sex at some stage in their life history. Aberrant sexual forms might therefore reasonably be expected to occur. In the present paper thirty hermaphrodite gonads encountered in an examination of 64,576 limpets are described and their significance in the wider context of sexual phenomena in molluscs is discussed.

Apart from a general account (Kon, 1954) of our work on vitamin A and carotenoids in invertebrates, our publications so far (Kon & Thompson, 1949a, b; Batham, Fisher, Henry, Kon & Thompson, 1951; Fisher, Kon & Thompson, 1951, 1952, 1953, 1954, 1955) have been concerned only with marine Crustacea. We have also studied, during our investigation of the metabolism of vitamin A and its possible precursors in the sea, numerous species from most other phyla of marine invertebrates. Except for the nematode worm, Anisakis physeteris Baylis, taken from the stomach of a sperm whale, the only two phyla of invertebrate animals in which we have so far found vitamin A are the Arthropoda and the Mollusca. The vitamin was present in at least some species from each of the molluscan classes, Loricata, Gastropoda, Lamellibranchiata and Cephalopoda, but we have no information yet about the Solenogastres or the Scaphopoda of which we have analysed no representatives. So far as our studies were concerned, the cephalopods differed considerably from the other molluscs examined, and the relatively large amount of information they have provided will be more conveniently presented in a subsequent paper. The account which follows, therefore, deals only with species from the first three classes just listed.

In our previous paper (Fisher, Kon & Thompson, 1956) on Mollusca we pointed out that the Cephalopoda were so different from the other classes in vitamin A and carotenoid relationships that they would be more satisfactorily considered separately. We have so far analysed ten species of cephalopods and found vitamin A in all of them. The studies of previous investigators of vitamin A in these molluscs were confined to its function in the visual cycle and to its contribution to the vitamin A reserves of sperm whales feeding on cephalopods. The carotenoids of cephalopods have been given even less attention than vitamin A.

On 30 July 1955 Dr J. H. Fraser, of the Scottish Home Department, Marine Laboratory, Aberdeen, sent to the British Museum for determination two adult females of a penaeid prawn collected at 01.56–02.0 h B.S.T. near the surface (15 fm.) at Rosemary Knoll, to the north-west of the Outer Hebrides, on 22 July 1955. The actual depth at this locality, 59° 12′ N., 10° 09′ W., is 229 fm (419 m). These specimens were identified by one of us (R. W. I.) as Funchalia woodwardi Johnson. Later the senior author confirmed this determination and wrote to Dr Fraser as follows:

The rate of circulation and age of the deep water of the oceans is of much interest. Worthington (1955) has suggested an age of 100–160 years for northern North Atlantic water which has reached the Carribean and Cayman Seas. I (in part. Cooper, 1955, 1956) have suspected that the rate of circulation of much of the North Atlantic deep water may be even faster than Worthington's results suggest. Provisional direct observations by G. Wüst & G. Dietrich (private communication) also suggest that the deep circulation is quite rapid.

Several methods have been devised for sampling plankton in the different water layers in the ocean, but for many years vertically hauled nets closed by a method devised by Nansen (1915) have fulfilled this purpose. Recently, however, an investigation by Barnes (1949) cast doubt on the validity of this method for quantitative work, and as in his paper he specifically referred to nets of the type used on the ‘Discovery’ Expeditions, the present observations were conducted to determine whether Barnes's findings were of general application to the method.

The polychaete Nereis diversicolor F. O. Müller is one of the most characteristic elements of the brackish-water fauna of north-western Europe, and inhabits an extremely wide range of salinities. As a background for comparative physiological studies of chloride regulation in worms from different parts of the geographical range, the writer has attempted to describe the salinities and the variations in salinity endured by populations of N. diversicolor in eco-logically distinct and geographically well separated areas. Three principal environments have been studied:

Detailed data have recently been given on the growth rate, under varying conditions, of the common barnacles, Balanus balanoides (L.), B. crenatus Brug. and B. balanus (L.) da Costa (Barnes & Powell, 1953; Barnes, 1955; Barnes & Barnes, 1954). This work has now been extended to Chthamalus stellatus (Poli). Some observations have been made on populations growing in their natural habitat, but most relate to animals growing under conditions of continuous immersion such as are obtained by exposure from a raft.

In a collection made with a 2 m stramin ring trawl at 47° 12′ N., 7° 40′ W. on 21 July 1955, with 450 fathoms of wire out, I have found two new species of medusae. These were each represented by a single specimen, one of which was an anthomedusa and the other a leptomedusa.

Broch (1913) described two new species of the coronate scyphomedusa Nausithoë from the North Atlantic, N. atlantica and N. globifera. Bigelow (1928, p. 498) was inclined to think that these two species might finally prove to represent extreme variants of the one species N. rubra Vanhöffen, though a much larger series of specimens in a better state of preservation would be needed to give a definite decision. Kramp (1947, p. 46) considered that N. globifera at any rate was a good species.

Maas (1903) described two specimens of a deep-water coronate scyphomedusa collected on the Siboga Expedition in the Malay Archipelago. He erected for these a new genus Paraphyllina and called the species P. intermedia. It differed from Periphylla in that the rhopalia were perradial and not interradial. In 1903, Lo Bianco figured a specimen taken in the Mediterranean near Capri which was identified for him by Maas as P. dodecdbostrycha (see also Maas, 1904, p. 48, footnote); Mayer (1910) saw this specimen and re-described and figured it as Paraphyllina intermedia. A fourth specimen ascribed to this species by Ranson (1936) was found washed up on the shore at Villefranche.

During a short visit of seven days to the Station Biologique, Roscoff, in June 1955, I was able to make some observations on living colonies of Merona cornucopiae (Norman) and on other hydroids. The object of my visit was to see living polyps of Tricyclusa singularis which were also found, but unexpectedly Merona was found during dredging and provided the opportunity for a much needed re-description from living material.

In a collection of plankton made by R.V. Sarsia, in a 2 m stramin ring trawl at 47° 12′ N., 7° 40′ W., on 21 July 1955 with 450 fathoms of wire out, there was a small anthomedusa which does not agree with any previously described species.