With the growth of modern, industry the problem of the influence of polluted waters on the bionomics of fishes is becoming very important. Fortunately, biologists anticipated this and many works on the subject have appeared, especially during the last twenty-five years. The polluting substances can be divided into two main classes, namely, (i) those that are directly poisonous to organisms, e.g. gas liquor, sulphites, oils, etc., and (ii) those that give rise to poisonous substances or otherwise make the water undesirable after putrefying, e.g. organic matter in solution and the decomposing bodies of plants and animals. The substances in the first category act in a relatively straightforward manner, and numerous investigators have studied them from several aspects (Shelford, '17; Matthews, '04; Powers, Wells, '15, etc.); it is with regard to those in the second class that many questions are yet unsettled and the present communication deals. We roughly know that the effect of the putrefying substances is to increase the hydrogen ion concentration and decrease the oxygen content of water. It has also been suggested that the byproducts of putrefaction themselves may be poisonous to animals.

While working on the beds in the River Blackwater, Essex, a collection of Portuguese oysters, which had been dredged along with native oysters (O.edulis) from the river and creeks, was seen at a glance to show a distinct average difference in shape from the usual type of Portuguese oyster. The ordinary Portuguese oyster as seen exposed for sale is usually im-ported when quite small, or occasionally well-grown, and relaid on English beds at or above low-water mark to grow and fatten. Orton* has shown by definite experiments on the same beds that the Portuguese oyster spawns and spats in English waters in favourable (hot) weather. There can be no doubt, therefore, that the Portuguese oysters dredged had grown in situ from larvae which had developed in the waters of the river and creeks. In Portugal and France the Portuguese oyster is stated to occur at and just below low water springs (see Bashford Dean, Bull. U.S.F.C. XI, 1891 (1893), p. 368), and is apparently hand collected at the present day for export purposes.

A difference in shape in native oysters is very common, but Bell and others have so far found it a very difficult matter to correlate any particular shape with a particular environment. Indeed, Bell stated, in a letter, that each locality seems to have its own type of shell-growth in the native oyster. Such a difference as that noted above in the Portuguese oyster was therefore deemed worthy of some attempt at expression.

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.

Powers, working on some marine fishes, arrived at the important conclusion that the ability of fishes to absorb oxygen at low pressures is more or less dependent upon the hydrogen ion concentration of the water. His method of research was briefly as follows: a fish was placed in a two-quart jar filled with water, which was closed airtight with a rubber stopper. The pH and the oxygen determinations were made immediately after all the movements of the fish had ceased. The amount of oxygen left at death represented, according to Powers, the pressure below which the fish at the particular pH could not extract any more oxygen from water. Powers did not control the amount of oxygen at the beginning of an experiment; he says, “it was always sufficiently high so that the fish did not at first suffer from oxygen want.”

Loxosoma phascolosomatum was first described under that name by Vogt (6) in 1876 when he discovered it at Roscoff on the posterior extremity of Phascolosoma elongatum and P. margaritaceum, where it forms a small tuft. It had probably been observed previously by Norman (4), and described by him in 1861 (3) as tentacular appendages of “Strephenterus claviger”; he found it on gephyreans dredged in 1858 from Bantry Bay. Barrois (2, p. 8) mentions that he also saw this species in 1874–75, before the publication of Vogt's paper, at Roscoff, where it was abundant on sipunculids. Since then it has been recorded as occurring on Phascolion by Andersson (1) in East Greenland, and by Norman (5) in East Finmark.

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.

1. Vegetable detritus of land and coastal origin is of notable importance as a source of food, especially to those specimens measuring 21-29 mm., which is the most abundant size found in the Clyde Sea Area.

2. Meganyctiphanes in the Clyde Sea Area for the most part lives and feeds between 10 and 20 fathoms above a muddy bottom, usually in waters about 60-80 fathoms deep.

3. Meganyctiphanes feeds by selecting from the surrounding water the suspended micro-organisms and detritus, and would thus come under the category of a “suspension feeder.”

4. The larger specimens measuring 29-31 mm. are found chiefly in Upper Loch Fyne. The largest specimens measuring 37 mm. are found exclusively in Upper Loch Fyne.

5. Adult specimens tend to decrease in numbers from May till September. During these months they appear to live during the day immediately above or on the muddy bottom.

6. The association of Meganyctijihanes norvegica, Thysanoessa raschii, Euchceta norvegica, and Calanus finmarchicus, in large numbers in Upper Loch Fyne would indicate that conditions there are specially favourable to all these species.

7. In Upper Loch Fyne M. norvegica, T. raschii, E. norvegica, and C. finmarchicus, make partial vertical diurnal migrations, specimens being found a few fathoms from the bottom during both day and night.

8. Under certain circumstances light appears to have a harmful effect on M. norvegica.

A new type of Nauplius belonging to Meganyctiphanes norvegica is described.

Attention is drawn to irregularities in the development of the furcilia forms in which particular stages are sometimes omitted.

It is suggested that in the larval history of M. norvegica in common with other Euphausids there is an indication of evolutionary progress in the group Euphausiaceæ.

It is difficult to rear crabs from the egg, and few experiments of the kind have been successful. It is intended in these studies of the Plymouth Brachyura to rear as many species as possible from the berried crab, and thus to ascertain without doubt the larvæ of each species in all stages, so that they may be recognisable in the plankton.

The members of the Oxyrhyncha so far observed in the Plymouth district are the following:-

Inachus Dorsettensis (Pennant), Inachus Dorynchus Leach, Macropodia longirostris (Fabricius), Macropodia Egyptia A. Milne-Edwards, Macropodia rostratus (L.), Achæus Cranchii Leach, Maia squinado (Herbst), Pisa biaculeata (Montagu), Hyas araneus (L.), Hyas coarcticus Leach, Eurynome aspera (Pennant).