In a former paper (Lebour, 1924) attention was called to the eggs, Calyptopis and first Furcilia stages of Thysanoessa inermis together with the form neglecta, which was regarded as a different species, mainly on account of the size of the eggs shed by the females in glass jars in the aquarium, those of the neglecta form being much smaller than those of the inermis form. Certain differences were also found between the males of the two forms.

Having through the kindness of Mr. C. F. Hickling obtained a number of Thysanoessa from the Atlantic Slope, chiefly in the region of the Smalls trawling ground, I found both forms present, which were usually much larger than those from the Channel, and presented certain other differences. Specimens of the two forms from both localities were sent to Dr. H. J. Hansen, of Copenhagen, who has kindly examined them and pronounced them all to belong to the same species,e.g. Thysanoessa inermis. It is an interesting fact that the specimens from the Smalls district are usually much larger than those from the Channel, and the neglecta form has the long legs much longer and stouter. Specimens from Iceland, for which I am indebted to Dr. Hansen, are also of a large size.

As Hansen has already pointed out (1911, 1915), Thysanoessa inermis which has a wide range of distribution has two forms, a short-legged form, formerly known as Rhoda inermisand a long-legged form, formerly known as Thysanoessa neglecta; these may be referred torespectively as the inermis and neglecta forms.

Always to be found in Drake's Island Tank.* Very abundant during the summer, but diminishing innumber during the winter months. It has been described by O. MÜller (22), Ehrenberg (6), Stein (31), Dujardin (5), Claparede and Lachmann (3), under various names, but their descriptions may be regarded as only of historic interest. The later observations of Gruber (13), Cohn (4), and Entz (8) aremore detailed, and Lebedew (17) has given the fullest account of the animal. Kent (16), Biitschli (1), and SchewiakofE (27) have only short notices.

1. The method of water sample preservation used by Gad-Andresen is not suitable for nitrite or nitrate estimation.

2. Using Buch's method it has been shown that the variation in nitrite during the summer is from less than 0-001 mg. to about 0-01 mg. per litre and that the deeper water layers have more than the surface layers.

The use of a mixture of copper soap, 5 or 10 per cent, with 1 per cent mineral oil, dissolved in petrol or benzol, increases the life of silk plankton nets by about four or five hundred per cent, and roughly doubles that of a hemp net for a single treatment. The beneficial effects last far longer than does the green colour. Re-treatment at suitable intervals is recommended.

The use of 5 or 10 per cent of resin * with an equal percentage of the soap improves its adherence to the fabric, as does also the addition of tar or anti-fouling paint. For silk nets, to avoid clogging, only one-half per cent of resin should be used with 5 per cent of soap.

A liquid soap mixture, which may be used with paraffin oil, can be obtained by adding one pound of resin to one pound of melted copper soap, and then dissolving in one and a half pounds of carbon tetrachloride. When wanted, this is used to make up a paraffin oil soap solution of the desired concentration, but adherence is less than with petrol.

1. A method of estimating nitrates in sea-water is described.

2. A considerable concentration of nitrates occurs in the depths of the ocean and a very low concentration (0 to 10 parts per 1000 million of nitrate-nitrogen) in the surface layers of those areas where there is no upwelling of water from below.

3. The nitrates in the water of the English Channel, twenty-two miles south-west of Plymouth, are almost entirely utilised by phytoplankton in the summer, and commence to be reformed from ammonium salts at a greater rate than they are utilised by the end of the summer.

1. The method of Dienert and Wandenbulcke permits of the estimation of silicate in solution down to the limit of 0-04 mg. of silica per litre, which cannot be distinguished from zero. The phosphate normally present does not interfere with the reaction.

2. All fresh waters examined were found to contain more silicate than does the water of the English Channel.

3. The water of Plymouth Sound is richer in silicate than that of the sea.

4. At Station El in the English Channel silicate decreases during spring, from a winter maximum of 200-240 mg. per cubic metre, so that from April to June, 1925, the amount left, recorded as 40 mg. per cubic metre, was indistinguishable from zero. At this time the water was stripped of phosphate also. Silicate increased again till early July, decreased in August and again in November ; the times of decrease are suggested as being those of diatom increase.

5. In deep Atlantic water silicate is much more abundant than in the English Channel; values from 360 mg. per cubic metre at 1000 metres to 1200 mg. at 3000 metres were obtained. In winter at any rate the surface value in the Atlantic is similar to that off Plymouth, about 110 mg.per m3 in 1925.

1. Horizontal hauls were made with a “stramin” ring-trawl and a silk net at different depths in 1924 and 1925 to determine the vertical distribution of the pelagic post-larval stages of Teleostean fish in daylight. The depths at which the nets fished on every occasion were obtained by means of a graphic depth-recorder.

2. It was indicated that there are specific differences in the behaviour of the post-larvae of various fishes as to their vertical distribution in daylight, some preferring the surface layers, others apparently indifferently distributed from surface to bottom, and others preferring the deeper layers and avoiding the surface; of these last it was found that some

species became abundant at deeper levels than others. A tentative list of distribution types is given on page 107. 3. Eesults emphasise the necessity when examining the horizontal distribution of young fish of sampling all layers : oblique hauls are to be desired fishing at as many levels as possible. 4. Mention is made of seasonal distribution : the year 1924 appeared to differ from 1925 in that certain post-larvae which were prevalent in the plankton well into June or July in the former year were cut short a month earlier in 1925.The post-larvae of Molva molva and of Lophius piscatorius were unusually abundant in 1924 ; post-larval Gobies (Gobiidce) and Wrasses (Labridce) were extremely scarce in 1925 during the months April to beginning of August.

1. The period of time which the oyster larva requires to attain its respective developmental stages was measured and recorded in 0. virginica and 0. angulata.

2. The development in various concentrations of salinity was studied in the three species, 0. virginica, 0. angulata, and 0. edulis.

3. In optimum salinity, all the impregnated eggs undergo segmentation and further development; the rate of development is uniform and its progress speedy.

1. A description is given of some measurements of the penetration of light into sea-water carried out near Plymouth in the autumn of 1925 by means of photo-electric cells, the current through the cell being, measured by a method, previously described, which is not affected by the motion of the ship.

2. The absorption coefficients found for off-shore waters down to 30 metres are smaller than the average of those found by several recent observers in various localities, but considerably larger than those found by Shelford and Gail for the deeper waters of Puget Sound. The coefficients tend.to increase with increase of depth, and are generally larger for in-shore waters. The clearest water, 20 miles out in the English Channel, gave an absorption coefficient 0-110 for the upper 10 metres, 0-117 for the second, and 0-133 for the third. This water, with glassy surface, transmitted 0-54% of the vertical illumination to 34-8 metres, 28-3% to 8-9 metres, at which depth a white disc was just visible, and 71-2% to 1-5 metres.

During 1925 dumpy oysters spawned in a high proportion on the Fal beds, and although not such heavy breeders as normal oysters, they are undoubtedly valuable in forming a stable spawning stock for replenishing the beds in the future. Nearly every normal and dumpy oyster above a size of 2 to 2\ inches produced at least one batch of spawn in 1925. Since dumps increase in proportion on the beds as over-fishing occurs, they form a natural breeding reserve for repopiilating the beds in favourable years, as there is no adequate reason to suppose that the larvae of dumps are unhealthy. Weekly samples of oysters examined closely during the summer of 1925 for the percentage of spawning females and ripe but unspawned females show

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.