1. The vertical distribution of many species in daylight in the Plymouth area is shown, as a result of the examination of a number of serial hauls taken with the stramin ring-trawl between the dates April 2nd and August 6th, 1926.

2. It is shown that probably the errors introduced by the employment of a non-closing net are for the present purpose negligible.

3. The indications are that most species have an optimum level at which they live, in the daytime, the actual depth varying from day to day according to weather and other conditions.

4. A few species appear to show no preference, being present equally abundantly at all depths or showing marked changes in the region of greatest abundance from day to day.

5. A provisional list is given on page 567, showing the order in which many of the different species appear in greatest abundance from the surface downwards.

6. The vertical distribution appears to differ for the two sexes of Calanus finmarchicus, the males tending to avoid the surface layers more than the females.

7. The presence of the medusa Cosmetira pilosella in fair numbers in a catch in the daytime in the Plymouth region would seem to be a reliable indication that the net has been fishing below 20 metres.

8. A catch of Calanus finmarchicus made by the stramin ring-trawl consists nearly always of over 80 per cent adults.

9. No attempt has been made definitely to correlate behaviour with external factors: more observations are to be desired.

10. Brief notes are given on the seasonal distribution of various species. The danger of drawing conclusions about seasonal abundance from daylight hauls only is shown by the results for Tomopteris helgolandica (p. 575).

1. Much of what was formerly considered to be phosphorus in organic combination, in sea-water, is in reality arsenic.

2. Certain analyses giving high values for phosphate in sea-water and a June minimum very far from complete exhaustion of phosphate are vitiated by the inclusion of arsenate, as arsenomolybdate, in the phosphomolybdate precipitate.

3. Arsenic in sea-water exists mainly in the form of arsenite. The arsenate present, if any, has hitherto been included in the results obtained for phosphate.

4. Since arsenic is found in algæ and has been recorded as increasing in quantity with increase of depth it seems that the arsenic present in sea-water must undergo seasonal changes.

The spatfall in 1924, as in 1923, was very slight and from the point of view of the oyster-producer was a failure, and was little better in 1922.

The growth of oysters in the summer of 1924 was unusually great; this has had the effect of bringing a large proportion of small oysters to a legally takeable size.

The dredging results have, therefore, been much better than they were expected to be in the season of 1924–25, but the effect has been to deplete the beds still more of reserve stocks of small.

Practically all the present stocks of small oysters are of a size between 2 and 2½ inches.

With only average growth in 1925 and 1926 a large majority of these small oysters will have attained a size which will not pass through a 2½-inch ring; hence the beds are in a dangerous state.

If, therefore, dredging continues under the present conditions, almost the whole of the present stock of small will have grown to large oysters and be cleared off the beds in the season of 1926–27.

It is shown that although oysters may grow to a size of 2½ inches at Falmouth in small numbers in three summers, yet four summers are required before a fair proportion of spat can be expected to attain a size of 2½ inches.

These notes record the result of work done at the Plymouth Laboratory during the summer of 1926. They deal chiefly with the feeding habits of Nucula, a Protobranch possessing the type of feeding mechanism characteristic of that order, and not found in any other Lamellibranch. During the course of my work I found Vlès' interesting paper on the sense organ of Nucula. After studying the organ, I arrived at a different interpretation of its function from that reached by Vlès.

The three common blennies of Plymouth are the Shanny, Blennius pholis, the Gattorugine Blenny, Blennius gattorugine, and the Butterfly Blenny, Blennius ocellaris. These have their habitat from just below high-water mark downwards. Thus, B. pholis inhabits the rocky pools from near high-water mark to the regions left dry by the tides; B. gattorugine is also to be found between tide-marks, but not so high up as B. pholis, and is more frequent in those parts uncovered by the spring tides; whereas B. ocellaris inhabits the deeper water and is always covered by the tide; it is frequently to be found on the dredging grounds in the region of the Mewstone and beyond the Breakwater.

The intestine of the Echiuroid worm, Thalassema neptuni Gärtner, is occasionally found at Plymouth to be infected with a small parasitic ciliate. I have searched the literature on the anatomy of Thalassema, but have been unable to find any reference to this Protozoon. In fact, I have not as yet come across any record of ciliates infesting the Gephyrea, though Mr. Dobell has informed me that, some years ago, the late Professor Ikeda mentioned to him the presence of ciliates from some of the Gephyrea he was then studying; but I have not been able to find any reference to ciliates in Ikeda's papers on Japanese Gephyrea. Lankester (1881), in a paper on Thalassema, merely records the occurrence of a gregarine which I also have observed in a number of specimens from the neighbourhood of Plymouth. I am, therefore, led to the conclusion that this ciliate must be new, and I have decided to name it Ptyssostoma thalassemæ nov. gen., nov. sp.

Measurements have been made of the hydrogen ion concentration of the muscles of various marine animals immediately after death and 20–24 hours after. The results obtained are of the same order as those previously found for the muscles of the frog and the cat.

In the years 1921 and 1922 a series of experiments on the rearing and hatching of the species of Rays and Skates occurring on the English side of the western end of the English Channel was carried out at the Laboratory of the Marine Biological Association, Plymouth. The egg-capsules were collected from fish landed at the Barbican at Plymouth and from fish captured by the Research steamers, Oithona and Salpa. The egg-capsules were kept in the circulation of sea-water in the tanks at the Laboratory, and for six species the period of incubation under these artificial conditions was determined.

In July, 1924, 250 floating, and an equal number of bottom-trailing, bottles were put out at selected places in the western English Channel. Fifty of each type were put out at each of the two routine Stations E2 and E3, and the same number was “liberated” at each of three selected stretches along the steamship route from Southampton to St. Malo. Those surface bottles, which did not strand locally, travelled rapidly up Channel towards the North Sea and across it. Many bottles arrived in the Skager-Rack after performing their journey of some 700 miles at the rate of 6 miles a day and more. An adequate study of wind conditions, as recorded at several stations along the length of the Channel and at one station in the southern North Sea, revealed the fact that there was, for some 5½ months (counting from the time of liberation of the bottles), an almost uninterrupted predominance of south-westerly winds—as recorded at all stations considered. The whole area of the Channel was swept by south-westerly winds of average speed of some 9 miles a day for at least 5½ months subsequent to the time of putting out of the bottles. July, 1924, had (according to the Falmouth Observatory records) the largest proportion of westerly winds experienced for 54 years; 20 days of this month had winds with westerly components. The association of the unusually persistent westerly winds with the rapid travel of surface bottles towards and across the North Sea is interesting.

The enzyme contained in the crystalline style of Pecten is destroyed more and more rapidly as temperature increases. On the other hand, it becomes more and more active if incubated at fairly low temperatures, possibly as a result of the progressive dispersion of the protein base on which it is absorbed. A graph has been calculated showing the effect of temperature on enzyme activity when both destruction and (?) dispersion are discounted.

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.

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.

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).