Acteon tornatilis is an opisthobranch mollusc which burrows in sand, using foot, labial and cephalic tentacles in the process. The last also help to exclude sand from the mantle cavity, which is extended into a caecum coiling alongside the visceral hump, presumably used for respiration but also for excretion. The main pallial water current is an exhalant one on the right.

The mantle skirt carries, on the left, numerous repugnatorial glands with toxic secretions.

Labial glands lie at the mouth and the buccal cavity contains jaws and a reduced buccal mass and radula. Into it open salivary glands the structure of which is like that of the pyramidellids. The oesophagus shows traces neither of glands nor of torsion whereas the stomach, though simplified, has resemblances to that of a prosobranch.

The reproductive system is shown to be different from previous descriptions. Male and female ducts are separate from the lower end of the little hermaphrodite duct. The former passes to a prostate from which a vas deferens leads to a large uninvaginable penis; the latter has associated albumen and mucous glands and there is a receptaculum seminis to the duct of which a ventral channel leads from the female aperture in the mantle cavity.Discussion of these aspects of the animal's structure confirms its position as the most primitive of the opisthobranchs.

On 26 November 1953 the new research ship Sarsia on her first cruise collected a number of Pontophilus echinulatus (M. Sars) (with an Agassiz trawl, depth 100 fm., La Chapelle, Bay of Biscay). Mr G. R. Forster, of the Plymouth Laboratory, noted that these did not fit into the key given by Kemp (1910) in that they have in the male a distinct appendix interna at the base of the four last pairs of pleopods, while in the female this is absent, the inner ramus being usually undivided, although occasionally an indistinct division can be made out. Otherwise they agree with Kemp's diagnosis.

Kemp (1910) notes M. Sars 1861 as authority, but this is only a preliminary description. In Sars (1868), given in Kemp's (1910) bibliography but not under the species, it is seen that he describes both male and female exactly as in the specimens from Sarsia, the male having a distinct appendix interna on the last four pairs of pleopods and an appendix masculina also on the second pair, the female pleopods having very short inner rami, except in the first which is long, and there is no appendix interna. Sars's figures of these limbs are very good. Kemp (1911) joins Philocheras with Pontophilus, and in this he is now followed by most authors.

Kemp (1916) reviewed the pleopods in the genus Pontophilus, as far as he could with the material he had in India, and he proposed certain groups according to the presence or absence of the appendix interna.

Results are given for measurements of fat, vitamin A and carotenoids in groups of Meganyctiphanes norvegica, Thysanoessa raschii, Crangon allmani, C. vulgaris, Nephrops norvegicus and eyes of Homarus vulgaris, collected at regular intervals for a year or longer.

In both species of euphausiids vitamin A was consistently present mainly in the ester form and concentrated chiefly in the eyes. More than half the total astaxanthin was in the eyes. No other carotenoids were detected.

Astaxanthin and vitamin A were accumulated by the euphausiids more rapidly during the spring and autumn-feeding periods associated with diatom outbursts than at other seasons. There was a delay in Thysanoessa raschii, but not in Meganyctiphanes norvegica, between resumption of more rapid growth during spring and autumn and increase in concentration of vitamin A and astaxanthin. The difference was possibly due to differences in diet of the two species in relation to the seasonal biological composition of the plankton.

In the euphausiids, concentrations of vitamin A and astaxanthin were much higher in larvae and in adults over 30 mm long of M. norvegica, and in larvae and adults over 15 mm of Thysanoessa raschii, than in mature adults of Meganyctiphanes norvegica of 20–30 mm and Thysanoessa raschii of 13–15 mm, respectively. An inverse relationship between fat and vitamin A concentration was noted in both species throughout the year.

In Crangon spp. and Nephrops norvegicus there was no evidence of any seasonal variation of either vitamin A or carotenoids. Differences in the carotenoid metabolism of the two species of Crangon are discussed.

Twenty-five years ago I published a note (Atkins, 1929) on a then unnamed member of the Saprolegniaceae, a destructive fungal parasite of the pea-crab, Pinnotheres; the name Leptolegnia marina is now proposed for this fungus.

Many brachyuran megalopae swim with the legs disposed in a curious manner. The chelipeds and first two pairs of walking legs are folded tightly beneath the body, while the two posterior pairs are wrapped over the dorsum, the third pair being stretched out anteriorly, the dactylus, according to its length, touching or being looped round the eye-stalk. It is suggested that this posture gives stream-lining to the megalopa and improves its swimming. The described arrangement has been observed in all but three of some twenty-five species occurring at Plymouth.

In the three exceptions, Corystes cassivelaunus, Thia polita and Pinnotheres pinnotheres (= veterum), all legs are carried folded beneath the body.

Reference is made to previous descriptions of the folding of the legs in the brachyuran megalopa.

Comments on the uses of penetrometers in general are followed by remarks upon an earlier one for use on dry beaches. Some discussion is given of the behaviour of beds of sand disturbed by shocks and converted thereby into a state of quasi-liquefaction. Finally, a description is given of a tall pull-down penetrometer which can be used on beaches covered by modest depths of water.

A method of representing the mixing of water in an estuary is given, and the amount of mixing which occurs in the Thames Estuary is calculated. Changes in salinity predicted from the results are found to agree with observation. The application of this theory of mixing to some pollution problems is briefly considered.

A survey of forty-eight species of British marine invertebrates has shown that porphyrins which have not previously been described in these animals are present in three representatives of the Annelida, two of the Mollusca and two of the Echinodermata. The occurrence of protoporphyrin in Asterias rubens was confirmed in a previous paper (Kennedy & Vevers, 1953b). A redfluorescent extract was obtained from the sponge Tethya aurantium, but it contained too little material for further investigation. No trace of a porphyrin was found in the coelenterates, crustaceans and tunicates examined, although Moseley found ‘polyperythrin’ (which MacMunn later identified with the ‘haematoporphyrin’ of Asterias and Arion) in Flabellum and Fungia.

Chlorocruoroporphyrin was found free in the starfishes Luidia and Astropecten. Uroporphyrin was extracted from the soft dorsal integument of Duvaucelia (= Tritonia) plebeia, and from the integument of Aplysia punctata, observations of interest in view of the widespread occurrence of uroporphyrin in mollusc shells.

Coproporphyrin III was characterized from extracts of the viscera of Myxicola infundibulum, Nereis diversicolor and Chaetopterus variopedatus. Evidence of the occurrence of a penta-carboxylic porphyrin was obtained from paper chromatography of the extract from the gut of Chaetopterus.

These findings are discussed in comparison with the distribution of porphyrins in birds and mammals.

Protostyela heterobranchia n.gen. n.sp. is a compound styelid ascidian from Scottish waters. The branchial sac has three longitudinal bars on each side and no folds, and the stigmata are transverse. Both hermaphrodite and unisexual (male) gonads are present.

Pelonaia corrugata in the Firth of Clyde breeds for only 2–4 weeks in January or February. The species is oviparous. Early cleavage is similar to that of other ascidians, but after gastrulation the embryo passes through a two-hemisphere stage. One of these hemispheres is endodermal. From the other hemisphere, which slowly envelops the endoderm, two ampullae grow and fix the embryo to the substratum. The young ascidian develops directly from this attached embryo, and the development is therefore anural. Elimination of the pelagic larval stage is regarded as an adaptation to the sand-dwelling habit of the adult, as it prevents dispersal to unsuitable habitats.

Surgical thyroidectomy has been successfully performed on the dogfish, Scyllium canicula, and has been shown to have no signficant effect on the animal's oxygen consumption over a period of 6 weeks.

The injection of extracts of dogfish thyroid into adult male white rats results in an increase in the animal's oxygen consumption of the same order as that produced by mammalian thyroid preparations.

The significance of these results is discussed in the light of recent investigations of thyroid function in fish.

The variable colour of Nereis diversicolor is due to variations in the proportion of green, orange and brown pigments. The orange and brown pigments are mainly carotenoids; the green colour is due to biliverdin.

Phaeophorbide-a and coproporphyrin III also occur, but both these pigments may be restricted to the gut wall; biliverdin occurs both in the wall of the gut, and in the epidermis and coelomic cells.

The biliverdin is formed by the breakdown of the haemoglobin of the blood.

Haemoglobin-breakdown takes place in the epidermis on the dorsal side of the body, in the epithelial tissue surrounding the proboscis and in the pygidium. Granules of biliverdin are probably removed by the coelomic cells and conveyed to the gut into which they are excreted.

In ripe males, and in females during and after spawning, phagocytosis of the tissues is accompanied by an increased haemoglobin-breakdown with a corresponding accumulation of biliverdin in the body. The green appearance is due not only to an increased amount of biliverdin, but also to a complete extraction of carotenoids from the body-wall.

In the heart of Marinogammarus marinus three systems of nerve elements have been found, viz. (1) a local system consisting of a ganglionic trunk situated on the dorsal surface of the heart and sending branches to the muscle fibres, (2) two paired nerves, termed the 1st and 2nd cardiac nerves, connecting the local system with the central nervous system, and (3) nerves supplying the muscles of the arterial valves. It is assumed that the local system rules the beat of the heart and that the cardiac nerves have a regulating function.

Not directly connected with the heart, but having relation to the blood circulation are two sets of nerves: (1) nerves supplying the alary muscles, presumably regulating the pressure in the pericardial cavity, and (2) nerves spreading over the lateral wall of the pericardium in neuropile-like plexuses and supposed to have a neurosecretory function.

It is suggested that the centre controlling the blood circulation could be localized in the infraoesophageal ganglion.

A marine fungus, Plectospira dubia n.sp., has been found infecting crustacean eggs and small Crustacea in the Plymouth Laboratory. It has the following characteristics: mycelium mostly intra-matrical, coarse, hyphae 50–100µ in diameter. Sporangia irregularly inflated, emptying by efferent hyphae of variable length and frequently of irregular diameter; sometimes proliferous; wall persistent. Zoospores dicystic and dimorphic, but the first swimming stage largely suppressed, the first zoospores mostly encysting within the sporangium after a short period of feeble activity, then swimming in the second stage. The first zoospores pyriform and flagellate (probably biflagellate): in the second motile stage laterally grooved with two laterally inserted flagella. First zoospores about 1oµ long, when encysted 7–8µ in diameter; in the second motile stage 11–12µ long, when encysted 6–7µ. in diameter. Gemmae numerous, spherical, up to 1OOµ. in diameter. Sexual organs so far unknown.

The urine secretion of the kidneys of Lophius piscatorius perfused with heparinized Lophius blood is very sensitive to perfusion pressure below a critical level, above which it becomes insensitive. The response of the urine flow to pressure takes the form of an exponential curve.

The blood flow through the kidneys, while rising slowly at pressures of about 20–30 mm of water, responds arithmetically to pressure above such levels.

At present it is impossible to make out whether pressure or blood flow has the greatest influence on secretion.

Water secretion in the aglomerular kidney is an active process. The oxygen consumption of the Lophius kidney is unmeasurably low, yet remains a possible factor in secretion.

Spirontocaris lilljeborgii is a dioecious species and no protandrous hermaphrodites have been seen.

The majority of males become sexually mature in the first year (7–9 months). Some of these may die after fertilizing the females and the majority die after fertilizing the females for a second year (18 months old).

Only a small proportion of the females breed in their first year, all breed during their second year and a few appear to live for a third year.

A first-year female lays from 130 to 160 eggs, and the usual output of a second-year female is from 450 to 650 eggs.

Egg laying begins at the end of November and hatching is complete by the end of March.

The total incubation period is about 90 days. Eye pigmentation first appears at about half the incubation period (47 days).

Juveniles can be distinguished as males and females by the shape of their pleopods within 4–6 months of hatching.