In connection with the cause of the unusual mortality of oysters reported on the oyster beds in the Thames Estuary in 1920 (see Min. Agric. and Fisheries Report, Fishery Investigations II, 6, Nos. 3 and 4, 1923–24, London), it is of interest to compare the simultaneous effects of known solutions of T.N.T. (Trinitrotoluene) in sea-water on both Portuguese and native oysters. In order to obtain some information on this problem the experiments described in the following pages have been carried out at the request of the Fisheries Department of the Ministry of Agriculture and Fisheries and with the help of the Government Chemist and his assistants.

The anatomy and histology of the food collecting and alimentary organs of the adult oyster are described.

The anatomy of the stomach is investigated with the aid of gelatin casts and attention drawn to the food caecum, the ventral groove, and the two ducts of the digestive diverticula.

Cilia and mucus glands are universal throughout the food collecting and alimentary organs.

There is evidence that the gastric shield is composed of fused cilia.

The histology of the style-sac resembles that described by Mackintosh for Crepidula. There is evidence that secretion of the style takes place in the groove.

Phagocytes are everywhere numerous in the blood vessels, connective tissue and epithelia, and free in the gut and mantle cavity.

The alimentary organs of the larva are described.

The anatomy and histology of these organs in the spat isdescribed, the palps are relatively large and the gills asymmetrical. The style-sac is distinct from the mid-gut.

The course of the ciliary currents on the gills and palps is described and the importance of the various selective mechanisms emphasized.Selection appears to be purely quantitative, large particles or mucus masses being rejected and smaller ones accepted.

Muscular activity is of great importance in the functioning of both gills and palps. Reversal of cilia has never been seen.

Rejected matter is removed from the mantle cavity.

Material is sorted in the food caecum in the stomach, larger particles passing into the mid-gut and smaller ones towards the gastric shield and ducts of the digestive diverticula, within the tubules of which there is a constant circulation.

The rotation of the style assists in the stirring of matter in the stomach.

In the style-sac are cilia, which rotate the style and others which push it into the storuach.

In the larva the velum acts as a food collecting organ ; the style lies in an extension of the stomach and rotates rapidly. Material passes freely into the digestive diverticula.

In the spat rejective mechanisms are highly developed. The style revolves at a speed of between sixty and seventy revolutions per minute.

The tubules of the digestive diverticula are the only place where soluble matter is absorbed, in adult, larvae, or spat.

Fine particles are ingested and digested intracellularly in the tubules of the digestive diverticula, the products of digestion carried away by amoebocytes, and useless matter rejected into the lumen.

Larger particles are ingested and digested by phagocytes in all parts, the products of digestion being carried to the vesicular connective tissue cells and there stored.

Enzymes in the style digest starch and glycogen. The amylase, at pH 5.9, has an optimum temperature of 43'C, and is destroyed at

The optimum medium is pH 5-9. It is inactivated by purification with absolute alcohol or by dialysis, but action is restored on the addition of chlorides or bromides and to a less extent iodides, nitrates, and carbonates, but not with sulphates or fluorides.

Sucroclastic enzymes in the digestive diverticula act on starch, glycogen, sucrose, raffinose, maltose, lactose, salicin, and amygdalin, but not on inulin, cellulose, or pentosans.

The amylase, at pH 5-5, has an optimum temperature of 44-5, and is destroyed at between 64 and 67. It has an optimum pH of 5-5, and is inactivated after purification or dialysis, action being restored in the presence of chlorides or bromides.

There is a weak lipase and protease, the latter has two optima at pH 3-7 and at or above 9-0 ; its action is very slow.

The only enzymes free in the stomach are those from the style.

There is no evidence of any enzymes free in the gill mucus.

There is a powerful complete oxidase system in the style, and a catalase in the digestive diverticula and gonad, and traces in the palps, gills, and muscle.

The style is the most acid substance in the gut and the cause of the acidity of the gut.

The style is dissolved rapidly in fluid of pH 2-3 and above, but very slowly below that point. It is readily dissolved and reformed in the oyster, its presence depending on the maintenance of the balance between the rate of secretion and the rate of dissolution. Its condition is a valuable indication of the state of metabolism.

Glycogen and fat are stored, particularly in the vesicular connective tissue cells, the former furnishing the principal reserve food material.

The presence of abundant supplies of microscopic plant life rich in carbohydrates provides ideal food for the oyster, and represents optimum conditions for fattening and reproduction.

Results are given of collections made with the stramin ring-trawl to study the vertical distribution of post-larval teleostean fishes throughoutthe period from daylight, through the hours of darkness, to daylight on July 15th-16th, 1924, and June 17th, 18th, and 19th, 1925. At the time of collecting in July, 1924, it was full moon ; in June, 1925, there was no moon.

In no case, except perhaps that of Sardina pilcliardus post-larvse, was there evidence of marked upward migration at night ; the general impression for most species was that while the type of distribution shown in daylight was somewhat modified at night, only very few individuals moved up to the surface layers. There was, however, a notable increase in numbers of certainspecies at all depths at night, whether this was an indication of a movement up from layers very close to the bottom is not known ; it will need many more observations before the exact significance of this can be fully understood.

The numbers of post-larvae taken were in the case of most species unfortunately very small on all occasions; it is not possible, therefore, to come to very definite conclusions.

A possible indication of the effect of moonlight was shown by the post-larval Callionymus lyra, for while in July, 1924, at the time of full moon they showed no upward movement at night, in June, 1925, with no moon a certain proportion reached the surface layers.

Results of collections with the ring-trawl to obtain evidence on the vertical distribution of plankton animals in daylight at different times of the year and at night are given.

The vertical distribution of Calanus finmarchicus and Cosmelira pilosella is discussed in relation to the distribution of light intensity in the sea.

Results show that light intensity is apparently the external factor of greatest importance in determining the vertical distribution of these plankton animals in this region.

Many more observations at sea correlated with simultaneous records of light intensity at different depths are required, together with laboratory experiments on the effects of various factors on the behaviour of plankton animals kept under different conditions of light intensity.

Apparently calcium carbonate is precipitated in certain parts of the ocean by processes which are inorganic in so far as that the calcium does not first form a true constituent of organisms (Clarke, 1920, p. 128). The conditions governing solubility of calcium in sea-water have been reviewed by Johnston and Williamson (1916) with the conclusion that surface layers of the ocean are approximately saturated, and that slight natural changes, particularly in carbon dioxide tension, might suffice to cause precipitation.

A comparison of the years 1923, 1924 and 1925 as regards the phosphate content of the water at Station El in the English Channel has shown that the vernal diminution was earliest in the year 1924, and latest in 1923, the extreme difference being approximately two months. These differences stand in direct relation to the spring sunshine, that of 1924 for the daily average of the 9th to 12th weeks inclusive being 2-3 hours in excess of the normal, 1923 being 0-1 hr. in deficit and 1925 being 0-6 hr. in excess. Since the phosphate diminution is proportional to the increase in phytoplankton the year 1924 must have been exceptionally early in this respect.

The year 1925 was in general similar to the other two in having a summer phosphate minimum and a winter maximum; but it was noticeable for marked periods of regeneration of phosphate, followed by utilization, within the main cycle.

The maximum value at El was 40 mg. per m3 of phosphate as P2O5, the minimum 5-1 mg. for thewhole water column, 0-70 metres.

Much additional evidence has been found to show that the deep water of the ocean is a reservoir of phosphate, containing 50-80 mg. per m3, or more.

The water of the North Sea was markedly richer in phosphate in the spring of 1925 than in that of 1924, as was also the water around the Faroe-Shetland Channel in July, 1925, as compared with the previous July. A causal connection may be sought.

In tropical waters the intense light normally results in the utilization of all phosphate down to at least 50 metres, and the winter cooling never suffices to effect mixing with the deeper water. At about 38N. latitude the water may be expected to be isothermal in winter to a depth of 350-400 metres, and further north the isothermal column has its base deeper down; accordingly the seasonal phosphate cycle must become more pronounced.

A small orange-coloured Enchytraeid Oligochaete has been known for some years to occur fairly abundantly in certain sheltered parts of the shore on the Cumbraes. It is also generally present, though scarce, on exposed parts of the shore. Hitherto it has been confounded with other species of Lumbricillus, but is now described as a new species.

Pinnotheres pisum is a small crab with a carapace between about 2−1 and 18 mm. wide. The females are commonly found parasitic in the mussel, Mytilus edulis, though they have been recorded from other bivalves. The males are free-swimming and are comparatively rarely found in mussels. These small crabs are never abundant, and not more than one female has ever been found in a mussel.

Texperiments are described which indicate that there is a physiological problem quite apartfrom the chemical problem of luminescence in the secretion of Malacocephalus Icevis(Lowe). The luminiferous substances are present in granules, which behave as though each were bounded bya membrane whose permeabilities resemble those of a typical cell, but differ from a cell in that they have little or no power of recovery from adverse conditions.

For optimal luminescence they require (i) a medium of a certain osmotic pressure,(ii) a certain range of alkalinity, (iii) a certain range of temperature, and (iv)abundant oxygen. Sea-water is not necessary for luminescence.

If they are exposed to extremes of acidity or alkalinity, or of hypotonic or hypertonic solutions, irreversible changes rapidly set in in the membrane of the granule, whereby the power of luminescence is lost.

In artificial conditions the rapid fading of the light from the initial brilliance is probably due to an increasing acidity caused by the accumulation of the products of oxidation.

An important part of recent investigations on herrings at Plymouth has been the collection of statistical data on the number of vertebræ, and when this report was written a total of 6869 fishes had already been examined with regard to this character. In the case of each of 105 fishes, however, the true number of vertebræ could not be stated with confidence, owing to marked irregularities in one or more vertebræ. These abnormal specimens are of more than passing interest. The abnormalities themselves are such that it would be well worth while to make a careful morphological study of “ fresh ” specimens to determine the extent to which nerves and muscles are affected. The determination of the distribution of abnormalities along the vertebral column suggests a possible explanation of the way in which they may have arisen. Moreover, there remains the question as to how the abnormal vertebræ should be counted when endeavouring to ascertain the true total number of vertebræ for statistical or genetic purposes. In the paragraphs which follow, the 105 cases of abnormality are described and their significance both in numbers and position discussed, but it should be remembered that all observations and measurements were made on dried skeletons, which had been prepared by boiling and cleaning.

Whilt working at the life histories of the euphausiids occurring in the English Channel, and also having had opportunities of examining the larvae of several other species belonging to different genera from various localities, the writer noted certain features in the larvae which usually enabled the genus to be distinguished easily. The chief specimens were obtained from plankton collected by Mr. F. S. Russell within a radius of twelve miles from Alexandria, Egypt, whilst working for the Egyptian Fisheries Department. The larval euphausiid material from this collection is rich, and an account of it will soon be published. In the meantime the following general notes are offered, as at present little is known of the systematics of euphausiid larvæ. As several workers are occupied with this group, so important from the point of view of the Fisheries, it seemed advisable to bring all that is known together. In so doing it has been found possible to form a working scheme, from which, being given a series of larvæ of any species, one is enabled to determine the genus. For this scheme the order of development of the pleopods has been taken as the main factor, as it is found that the pleopods develop differently in several of the most important genera.

The apparatus described in this paper has been specially designed for the taking of samples in cases where it is important that the finer constituents of the sample should be adequately retained. In commencing a study of the micro-fauna and micro-flora of the sea-bottom near Plymouth the writer found that, in samples taken by the “Petersen” (2) 1/10 sq. metre bottom-sampler, or by the, conical dredge, the silt and finest material was liable to be washed away to a variable and non-measurable extent while hauling the apparatus. Quantitative observations on very small organisms were judged impossible by these methods and attention was directed towards devising an apparatus which would retain the finer portions of the deposits.

The Council and Officers.

Four ordinary meetings of the Council were held during the year at which the average attendance was twelve. All the meetings were held in the rooms of the Eoyal Society, and the Council wishes to express to the President and Council of the Society the thanks of the Association for the facilities provided.

The Plymouth Laboratory was visited and inspected by a Committee of six members of the Council in March. The Building Committee has also had several meetings in connection with the building of the new laboratories.