As a serpulid, Pomatoceros triqueter L. realises to the highest degree the adaptation to a sedentary life. The calcareous tube in which this annelid lives is characterised by a keel running along its upper surface. It is rather misleading to say that this tube is triangular in section. Figure 2 shows a newly formed calcareous rod; it is spur-shaped; the two rami of the spur might approach each other so nearly as to simulate an almost complete tube. The substratum in this species not only serves as a support, but completes the tube. This is in accordance with the fact that the tubes of Pomatoceros never extend freely off the support as happens with tubes of other serpulids–Protula, for instance. The aim of this paper is to record some observations on the way an adult Pomatoceros endeavours to build a new calcareous tube if it is artificially removed from its old one. I undertook this observation as original work at Roscoff, where a complete literature was not available. I discovered later that Harms, in the course of his research on regeneration in Hydroides pectinata, arrived at identical results. My paper cannot therefore pretend to more than a confirmation of previous results.

In a previous paper (Lebour, 1930) the general characters of the larvæ of Galathea were described and the various stages of Galathea strigosa and Galathea dispersa identified. The present paper deals with the larvæ of Galathea squamifera and Galathea intermedia which have also been followed through their life histories. This completes the larvæ of the Galatheidæ from Plymouth with the exception of Galathea nexa, the larvæ of which have not been seen. As is noted in the previous paper this Galathea is regarded as a separate species from G. dispersa.

1. Details are given of the results of a series of hauls with the 2-metre stramin ring-trawl fished at six different depths in daylight, at dusk, in the dark, at dawn and again in daylight on June 3rd–4th, 1926.

2. A comparison is given of the results obtained on the four nights July 15–16th, 1924; June 17–18–19th, 1925, and June 3rd–4th, 1926.

3. The importance is stressed of the effects on the type of behaviour shown by any animal produced by the depth at which it is living in the daylight and the speed at which it can swim upwards.

The following is a report on the Cœlenterate plankton taken off the Northumbrian Coast in 1924 during cruises of the Evadne of the Dove Marine Laboratory, Cullercoats, Northumberland. The work has been carried out under the supervision of Professor A. D. Peacock to whom I am indebted for much helpful advice. I must thank Professor A. Meek of Armstrong College, Newcastle-upon-Tyne, for so kindly providing the material, and Miss M. Yeats for the use of her notes on the 1924 surface medusae. Mr. P. L. Kramp of Copenhagen was so good as to check my identifications of certain specimens hitherto unnoted from Northumberland, and for this service I express my obligation. Dr. Allen, Director of the Plymouth Marine Biological Laboratory, and Capt. Totton of the British Museum, have also been kind enough to assist in questions of nomenclature. My own work consisted of the investigation of middle and bottom water samples and Miss Yeats' results on surface samples have also been incorporated here to make the yearly report complete.

The pteropod Clione limacina (Phipps), now regarded as one of the tectibranchs, occurs at times in the neighbourhood of Plymouth. In 1930, however, it was extraordinarily abundant, especially in the summer, and was breeding freely. Although not specially recorded it has been seen singly or in small numbers in almost any month of the year, and for some years the eggs and larvæ (not recognised at the time as belonging to Clione) have been seen in summer. So far it is known from the British coasts in the North Sea and the west and extreme south-west of England. Its distribution, as known up to 1908, is given fully for the area of International Fisheries Investigations by Paulsen (1910). There it is shown that it is an Arctic-boreal species, spreading southwards nearly to the Bay of Biscay, which is about its southerly limit. It is known to occur in the northern and mid North Sea, but not in the southern North Sea, and at that time was only recorded from the Channel in the extreme west. It is also common in the Atlantic. Paulsen was led to infer that Clione limacina did not enter the North Sea from the Channel, but its prevalence sometimes at Plymouth shows that it can come a long way up the Channel and, as few samples are taken to the east and in the southern North Sea, this view should be carefully reconsidered.

1. The diurnal behaviour of Sagitta of different sizes is shown as a result of collections made with the 2-metre stramin ring-trawl throughout 24 hours on July 15th–16th, 1924, and on June 3rd–4th, 1926.

2. The younger stages of Sagitta elegans appear to withstand higher intensities of light in the daytime than do the older stages, and they migrate first to the surface at dusk, as do those of Sagitta setosa. The older stages leave the surface first at dawn.

3. Diagrams are given showing the curves of equal intensities of light beneath the sea surface throughout 24 hours as calculated from air intensities obtained in June, with a reflection loss of 15%; (a) assuming a coefficient of absorption of 0·200 at all depths, and (b) assuming a coefficient of absorption of 0·100 at all depths.

4. It appears, from a comparison of the behaviour of Sagitta elegans with the calculated light conditions beneath the surface, that the older Sagitta at any rate are more sensitive to light in the early morning after the darkness of the night and can become adapted to light of higher intensities later in the day.

5. Previously published observations on the behaviour of Sagitta sp. on June 17th–18th–19th, 1925, show quite a different type of behaviour from the above, possibly due to more transparent water, the Sagitta only appearing abundantly above 30 metres in the dark. They had again migrated to below 30 m. before there was any appreciable light.

This is a report of the Cœlenterate plankton taken during the cruises of the Evadne in 1925, and investigated at the request of Professor A. D. Peacock. I am indebted to Miss Ann R. Sanderson, B.Sc., for considerable help in the identification of specimens.

In recent years attention has been given to the influence of electrical currents as fish deflectors or screens, and experiments have been made to determine the magnitude of the currents which are sufficient to paralyse or act as deterrents to fish which may enter the electrical field, but in such strong fields the perception of the mechanism by which fish respond to electric currents is masked by the paralysis produced. It seemed possible that experiments with very weak currents might give fuller information concerning the mechanism by which fish respond to electrical stimulus than those made in strong fields. There is also the possibility that weak electric currents may occur in nature to which fish respond, but before exploring that field of phenomena it is necessary to observe the behaviour of fish under the influence of very weak fields. McMillan found that the field (volts per inch) required to paralyse young salmon varied with the resistivity of the water; thus when the latter was 10,000 ohms per inch cube the paralysing voltage was about 1·5, so that a current density of ampere per square inch was sufficient to cause paralysis, whereas when the resistivity was twelve ohms per inch cube the current required was ·03 ampere. In the former case the conductivity of the fish was greater than that of the water, in the latter case less.

The two species of Nassarius (usually known as Nassa), N. reticulatus and N. incrassatus, are both common at Plymouth. N. reticulatus, the larger species, occurs from low water usually to a depth of a few fathoms, more rarely from the waters outside the Breakwater, N. incrassatus occurring between tide-marks and extending into deeper water, even to 46 fathoms.

In July–August of three different years common surface-floating bottles were set adrift at International Station E2 (49° 27' N.—4° 42' W.). With them, various types of drag-fitted bottles were also put out. The journeys accomplished are discussed, and the striking differences as between year and year in the case of the common surface floaters, and as between the different types in the same year, are commented upon in the light of the prevailing winds. An inter-relationship of great simplicity is deduced between wind speed and the rate of travel of simple surface floating bottles up-Channel and across the North Sea from the results of experiments carried out in four different summers.

In 1926 Pelseneer discovered the eggs of Trivia europea on the French coast. These he found were laid in capsules embedded in the compound ascidian Polyclinum luteum, the molluse biting a hole and laying its eggs in a vase-like capsule completely enveloped in the ascidian except for the wide lip of the vase which projects freely and can be easily seen with the naked eye (Pelseneer, 1926, Figs. 11–12). He also hatched some larvae from these eggs which were very interesting, as they possessed an accessory shell somewhat similar in shape to the Echinospira of Lamellaria perspicua. He did not obtain the eggs directly from the Trivia and was not able to keep the larvæ alive more than a few days. In his paper he expresses the hope that some worker will confirm his observations experimentally. This I am now able to do, having procured the eggs actually laid by the Trivia, hatched them out and kept them alive for more than a week, afterwards collecting the larvæ from the plankton from stages which exactly corresponded with those from the egg up to late stages which metamorphosed into young Trivia, and young stages of Trivia feeding on compound ascidians which corresponded with the metamorphosed forms.

Trivia europea is common at Plymouth between tide-marks and in a few fathoms of water; occasionally further out in deeper water. Records are available from the shore to the region beyond the Eddystone.

1. Among schooling fish, the younger stages of the bass (Morone labrax) provide an instance in which the schooling habit, though strong, is not stereotyped into fixed forms of behaviour.

2. Observations were made on individual fish in connection with their attraction for one another, a special point being made of observing their behaviour in front of a mirror.

3. The data so obtained are summarised in the light of their bearing on the problems of school formation.

In both the series of hauls made for the purpose of estimating the reliability of a single haul of the International Vertical Net, the possibility that the variation in the size of catch of successive hauls is due to errors of the methodique has been examined.

Errors due to variations in the speed of hauling, and to the effect of light and darkness on the catch of the net can be ruled out.

The enumeration error, even where the enumerated total rests on a single count, is insufficient to account for the major part of the variations found, and, having regard to the fact that such totals were derived from two, and sometimes more, separate “counts” from each sample, there is good reason to believe that the main cause of variation in the size of catch is to be sought elsewhere, the most likely being the lack of uniformity in the distribution of the organisms themselves.

Plasmodia of Labyrinthula almost invariably appear in the diatom cultures and other small marine aquaria which I have kept during the last several years for a variety of purposes in Glasgow. These aquaria are stocked with material from Millport, I. of Cumbrae, and I think it quite certain that the Labyrinthula is imported thence.

This amazing creature has attracted interest ever since it was first described by Cienkowski in 1867, and good figures of it have been published by Cienkowski (1867), Duboscq (1921), and Valkanov (1929). The following note is to be regarded as a commentary on previous work and a record of my own observations rather than as an exhaustive account of the organism.

(1) Cotton and linen fabrics were exposed horizontally on the Laboratory roof at Plymouth for two years. During this time the fabrics lost from one to two-thirds of their initial tensile strengths in both warp and weft.

(2) The application of copper oleate, mixed copper soaps, also of the latter with resin or tar as binding agents, had no effect or a slight effect only in lessening deterioration; such weakening must therefore be due to weathering, chiefly the action of light, since these substances have been shown to be useful antiseptics on nets immersed in salt or fresh water.

(3) No deleterious action may be expected when nets treated with these substances are exposed to light, since the treated fabrics were no weaker than the untreated; but where Cuprinol had been used, there appears to have been some weakening, though the antiseptic properties of Cuprinol are excellent.

In a small collection of sponges obtained during the winter of 1930–31 at Plymouth, six specimens were found which are of special interest. Four of these have proved to be new to the locality, the fifth was new to British waters, and the sixth was found to be a new species. Those species new t o the Plymouth area are Gellius angulatus (Bowerbank), Pachymatisma johnstoni Bowerbank, Eurypon clavatum (Bowerbank), and Halichondria firmus Bowerbank. The latter is the first example of the species to be recorded since it was first described forty years ago. The species new to the British waters is Reniera aquœductus Schmidt, and the new species Pseudaxinella alleni n.sp.

The insects, Scatella stagnalis, for the present study were collected from the Marine Biological Laboratory at Plymouth at the kind suggestion of Dr. Allen, F.R.S., the Director of the Laboratory, during my short stay there in the summer of 1929. So far as I can see, no work on the early stages of the genus Scatella is available. This led me to put on record the present account of the different pre-imaginal stages of the insect Scatella stagnalis in the following pages. I have described here only those stages that are exhibited in my hurried collection which may not be complete. A study of its complete biology would be of considerable interest; this, however, requires a constant watch of the species at the spot for a fairly long period.

Somewhere about 1914 D. J. Matthews maintained the sea-water in the Plymouth aquarium tanks at a pH value close to that of the outside sea-water by the addition of suitable quantities of sodium carbonate.