On October 28th, 1920, a conjoint meeting was held by representatives of the Development Commission, the Ministry of Agriculture and Fisheries and the Oyster Merchants and Planters Association to institute investigations into the cause of the abnormal mortality which had occurred among oysters in the oyster beds in the Thames Estuary during the summer of 1920. As a result of this meeting investigations were begun under the general direction of the writer. On the completion of the work a full report of the results obtained was forwarded to the Fisheries Department, Ministry of Agriculture and Fisheries. The more important parts of that report will be published as follows: Part I, Main Report, Fishery Investigations, Ministry of Agriculture and Fisheries, London, Series II, Vol. VI, No. 3, 1923; Part II. containing the more important Appendices, will appear later.

Of the relation of amœboid movement to other forms of contractility, very little is known at present. Hypotheses have been advanced to explain the movement, but they differ widely among themselves, and are founded almost entirely on direct observations of the normal activities of amœba. More recently Loeb (24) (25) and others have tried to determine the rôle of various environmental factors, such as the presence of certain salts, in amœboid activity. It is on these lines that the present work is being conducted.

Last year preliminary results on the feeding of some of the commoner plankton organisms were published (1922). Further progress is made this year, more especially on the living animals, chiefly cœlenterates, kept in the plunger jars. The results of these experiments, specially undertaken to find out whether medusæ naturally caught and ate small fishes, answer the question undoubtedly in the affirmative. A large number of the smaller medusæ were kept alive, and most of these were seen to catch and eat fishes. The usual method of catching the food is with the outstretched tentacles, which, drawn out to very fine threads, react when anything living touches them, stinging the prey with their stinging cells; the tentacles then contract and helped by others, and often also by the lips and sides of the umbrella, manage to convey the food to the mouth, from which it reaches the stomach and is digested. A certain amount of selection is apparent, for the tentacles often reject food. Moreover, medusæ of one species do not as a rule eat one another, although taking other species voraciously. If many small fishes are available the smaller crustacea are neglected by many of the medusæ, although these may be taken when other food is searce. Sagitta bipunctata and Tomopteris helgolandiea are popular with nearly all those that can eat fishes. Certain medusæ, e.g. Sarsia tubulosa and S. prolifera, have never been seen to eat anything but crustacea (copepods or decapod larvæ), and fishes have not been seen inside them.

In the first publication under the above general title the seasonal changes in sea water were studied, but as explained previously it was not possible to regard all the data as of an equal degree of accuracy. For this and other reasons the seasonal changes were further traced in the hydrographical cruises up to October, 1922, when the approach of the winter equilibrium made it profitless for some months to continue. Since, however, at times from April to September the changes are relatively rapid it may be advisable to follow up the matter during the period mentioned at shorter intervals.

On account of the minute quantities in which they are present and of the fact that they are considered of secondary importance as indicating sewage contamination, phosphates are not usually estimated in analyses of natural waters. The tediousness of the determination also militated against it in the past. As a result, of the numerous analyses recorded by Clarke (1920), but few mention phosphates. C. H. Stone's analysis of the Mississippi in 1905, carried out upon a sample above Carrolton, Louisiana, shows 0.27 per cent of phosphate (PO4) with a total salinity of 146 parts per million, or 0.39 mgrm. PO4 per litre, corresponding to 0.29 mgrm. P2O5.

When studying the seasonal changes in the algal plankton in relation to the supply of the constituents necessary for their growth, one is led to seek the source of the silica used to form the valves of the diatoms and to consider whether lack of silica might be a factor limiting their multiplication.

In a former paper (1922) it was shown that the pH value of stored sea water decreased owing to the production of carbonic acid by organisms in it, and the oxidisable matter as indicated by this biological method appeared to be higher than the result obtained by oxidation with permanganate, according to various analyses available for comparison. These, however, were not done on the same water, so an attempt was made to determine this quantity on water of the English Channel off Plymouth. As is well known the permanganate method gives results which vary appreciably, according to the conditions of the experiment.

From May, 1922, onwards the sq. metre bottom-sampler has been used to collect samples of the bottom-deposits with their animals, in the waters off Plymouth. The animals have been removed as soon as possible after capture by passing the samples through a series of sieves, and have been preserved in alcohol, to be identified and counted ashore. The present report deals with the distribution of the species represented, in the light of Petersen's Community investigations in Danish waters.

I express my thanks to Dr. Allen, Dr. Orton, Mr. Hunt, and Mr. Smith, of the Plymouth Laboratory, for their kind help in the identification of the material. I am particularly indebted to my friend, Mr. R. Winckworth, a late member of the staff, who has not only gone over with me the bulk of my collection of lamellibranchs, but has provided me with an excellent type series as complete as the material would allow.

The extensive use of his bottom-sampler in Danish waters and elsewhere has enabled Dr. C. G. Joh. Petersen to advance an opinion that “as a rule it is best to regard the animals living on the sea-bottom as communities, just as botanists group together the vegetation of the land into plant communities, even though in the present state of our knowledge it is impossible to show how intimate the mutual relations are between the animals of the sea in the single cases.”

It will probably assist the reader if I commence with a short summary recalling the more important points, concerning the recognition of communities, which have been advanced by Peterson, and in doing so I shall adhere closely to his own words.

Data obtained during the cruises of the s.ss. Huxley and Oithona in the years 1903 to 1906 indicated a general seasonal movement of water into and out of the mouth of the English Channel. It was found that in the autumn, somewhat sooner or later and to a greater or less extent each year, water, of the high salt content characteristic of the open Atlantic in the north of the Bay of Biscay and to the south-west of the English Channel, began to move in a north-easterly direction into the mouth of the English Channel, extending in a tongue along the centre of the Channel and into the Irish Channel, which is characterised by water of lesser salt content.

This general movement of relatively high salinity water continued during the winter until the spring or early summer, when water of lesser salinity moved southward from the Irish Channel across the mouth past Ushant, and to some extent into the English Channel; the condition in August being that water of relatively high salinity which had entered the Channel during the winter months was cut off from Atlantic water of equal salinity by a less saline water-mass extending south from the Irish Channel.

These general movements have been deduced from the data collected during the cruises in February, May, August, and November. To accurately depict the changing conditions and follow the movement of the water year by year would require frequent observations, more or less simultaneous, over a wide area—a condition of perfection which in practice could not be obtained without the use of several ships working almost continuously and in conjunction.

The short investigation here described was made in March and April, 1922, during the spring mackerel fishing season off the Cornish coast, in order to discover whether the opinion of Skipper Wylie, of Lowestoft, (drifter, Realize) was justified. In his opinion the best catches of mackerel were made wherever his thermometer showed him a sea surface temperature higher than that of the neighbouring water.

About a dozen drifter skippers, who volunteered to undertake the work, were given thermometers, graduated in ⅕° C. (about 20 graduations per cm.) and forms upon which to record their observations, and were shown how to take a surface sample and read its temperature. These thermometers were not very suitable, since the range was too great, and therefore the scale too small. They also suffered from the defect that the mercury thread easily become broken, and if the detached portion ran down into the bulb at the top of the tube, it was difficult to ensure that all the mercury came out again, and that the thread made a proper joint.

The forms used (p. 241) were based upon the log books used during the investigations on pelagic fishes from 1895 to 1911* (Russell, 1915). It was hoped that sufficient data would be collected in the course of a month, but, although the experiment was extended into April, only 32 records are available, covering the period 9th March-19th April.

These records are tabulated in Table 1. In those cases where the temperatures at the times of shooting and hauling differed, both the values are given, but their mean has been used in computing averages.

It was observed during the summer of 1920 that specimens of the Long legged Spider-crab, Stenorhynchus phalangium Penn., which happened to be in the crowded tanks of the Roscoff Laboratory, were always to be found in the neighbourhood of specimens of Anemonia sulcata Penn. (Anthea cereus Ellis). That this was not merely accidental was shown when crabs, removed to a distance of over three feet, returned time after time to an Anemonia, passing on the way anemones of various species, as well as all manner of objects which might conceivably afford shelter. Of fifteen healthy crabs of this species observed during the past three summers, every one showed this tendency in greater or less degree. At least two of these crabs were found clinging to anemones of this species on the shore, between tide marks; but the subsequent behaviour of crabs dredged from deeper water was in no way different.

The material upon which the following account of the development of P.canaliculata is based was mainly obtained in 1902 when working in the Laboratory at Plymouth. The larvæ were first noticed, and their identity suspected, in April of that year, and identification was made certain by keeping the larvæ in the “mysis” stage until they moulted into the post-larval form, some individuals being kept also through several subsequent moults. The intermediate stages were all taken from the plankton, since I was unable to hatch the larvæ from the egg. The only egg-bearing female seen at that time was taken on the Eddystone Ground on April 29, and her eggs were so far advanced that, although she was unfortunately killed, a few larvæ escaped from the eggs and made it possible to obtain some idea of the structure of the first zoæa.

During a short stay in Plymouth during April, 1922,1 was able not only to pick out a few more specimens from the plankton then brought in, but also, by working through a large number of preserved plankton samples, to obtain a considerable amount of additional material, mainly of later stages. A few specimens have also been found in samples of plankton from the North Sea preserved at the Fisheries Laboratory at Lowestoft, for the loan of which I am indebted to Mr. A. C. Hardy. But the larvæ of this species are much rarer in the North Sea than in the neighbourhood of Plymouth, where they are quite common.

The well-known Peridinium ovatum (Pouchet) is a common and widely distributed species. It was first described by Pouchet (1883) from the Mediterranean, and later more detailed figures were given by Schütt (1895), Fauré Fremiet (1908), and Broch (1909). None of these figures agree with the plate arrangement found in the specimens from Plymouth. Jörgensen (1913) places the species in his section Humilia in the group Metaperidinium, on account of the supposed arrangement of the dorsal epithecal plates.

A small coccosphere occurs abundantly in centrifuged water samples from the Plymouth district, the western part of the Channel, and outwards towards the Irish Sea and the French coast. This agrees with the species described by Ostenfeld (1899) as Coccosphœra atlantica, from the North Atlantic, which Lohmann (1902) considers identical with Wallich's Coccosphœra pelagica (1877). Lohmann, therefore, unites the two species as Coccolithophora pelagica, and in this he is followed by Ostenfeld (1908), the generic name of Coccosphœra being preoccupied by Perty (1852) for a small green flagellate.

The chief difference between C. pelagica and C. atlantica is in the number of coccoliths (16 to 36 in the former, 10 to 17 in the latter). The overlapping of the margins of the Coccoliths in C. atlantica is another difference, but it appears likely from Wallich's drawings that he had only taken the inner margins into consideration, and, therefore, regarded the coccoliths of C. pelagica as not overlapping. His measurements, which cover an extensive range, embrace those of C. atlantica. It seems, therefore, that C. atlantica is to be regarded as the same species as C. pelagica, the coccoliths having a similar form, and that Lohmann and Ostenfeld are justified in bringing them together.

Coccolithophora pelagica thus includes Murray and Blackman's C. pelagica (1898), Huxley's “Coccospheres” (1868, Plate 4, Figs. 6, c, d, e, and 7, b and c), and Ostenfeld's C. atlantica (1899, 1900). The coccoliths described by Joly and Dixon (1897) and the coccospheres by Dixon (1900) from the Irish Sea also belong to this species.

Owing to the combined action of bacteria, sunlight, sea-water, and general wear and tear the costly silk tow-nets when in constant use are only found to last a few months, or with less use for over twelve months. The young fish trawl-nets, made of a hemp material known as “stramin,” if used several times a week are expected to last over three months.

An apparatus was devised with the primary object of determining the atmospheric nitrogen and oxygen dissolved in sea water from on board ship in fine weather. It was found that the apparatus could be used at sea in fine weather, but owing to the difficulty of manipulation when any sea was running there was a possibility of error which necessitated duplicate determinations being made, each of which took about twenty minutes. In the Laboratory, on the other hand, the apparatus gives rapid and reasonably accurate results, and may be of use for the estimation of oxygen or other dissolved gases in fluids which contain organic matter, rendering Winkler's method of oxygen determination impossible, and where there is an insufficient quantity of fluid and time to carry out extraction of the gases by means of a mercury pump.

The apparatus was made as shown diagramatically in Fig. I, consisting of a glass bulb filled with mercury, with the necessary means of evacuating it and trapping any air leak which may occur in the process. It is mounted in a weighted teak box with hinged door and can be let down by a line to any desired depth in the sea, the tap t opened by a messenger and the charge of sea water (4.59 c.c. in this particular apparatus) drawn in, as shown in Fig. II. The apparatus is then drawn up, tap t and screw pinch cock s closed, and the bulb evacuated by lowering the mercury reservoir and opening tap q (Fig. III).