1. Measurements of hydrogen ion concentration, of phosphate concentration, and of temperature all show at certain seasons a well-marked gradient from surface to bottom. The upper 10–20 metres is more alkaline, notably depleted of phosphates and warmer.

2. Settled summer weather and deep water, free from irregularities of the bottom, favour the formation of such a gradient. Its breaking up is occasioned by wave action and the cooling of the surface water in autumn.

3. Thermal stratification in the English Channel arises at each station, and is not due to the inflow of warm over colder water.

The Herring season of 1923–24 was a peculiarly good one, the fishery continuing from the end of October into the beginning of February.

Newly hatched Herring were first observed on December 17th, 1923, and post-larvæ were abundant up to March, 1924, in the neighbourhood of Plymouth.

Investigations were made into the food of these young Herring, and the probable depth at which they were feeding. Hauls with Young Fish Trawl were made near the surface, midwater, and near the bottom, and tow-nettings were also taken. It has, however, now been found by Mr. Russell that the samples assumed to be near the bottom were possibly in reality some distance above it.

(1) The effect of temperature on the viscosity of the protoplasm has been determined in the unripe eggs of Nereis diversicolor by the centrifuge method.

The viscosity rises as the temperature falls, the rise becoming rapid near 0°C.

(2) These changes of viscosity with temperature are similar to those described by Weber (21) in the protoplasm of certain plant cells.

(3) Attention is drawn to the fact that the temperature coefficients of biological processes should be corrected for the viscosity of the protoplasm in which they occur.

(4) It is shown that the relative changes of protoplasmic viscosity with temperature are probably of the order required to make the temperature coefficients of biological processes constant when corrected for the viscosity factor.

(5) The magnitude of the temperature coefficients of biological processes when corrected for viscosity changes is probably of the same order as that of the temperature coefficients of a chemical process when corrected for changes in the viscosity of its medium.

Many of the difficultics found in naming and classifying Crustacea are due to the extraordinary modifications caused by growth and sex, and the confusion arising from our lack of knowledge of these developmental stages has led to many errors.

An investigation into the euphausiids in the Plymouth waters was undertaken on account of the fact that on examining adult Herring for food it was found that Nyctiphanes Couchii (Bell) was of great importance, and occurred in enormous numbers in a large proportion of the Herring caught in the earlier half of the period of the Herring fishery.

The Zoea of Eurynome aspera has already been twice described—namely, by Kinahan (1857) and Cano (1893), but there is some discrepancy between the two accounts which an observation made at Plymouth in April, 1922, fully explains.

Kinahan observed the larva immediately on hatching and described it as having neither rostrum nor dorsal spine; whereas Cano describes it as having both.

The present paper is a continuation of the work already published under the above general title and should be considered in relation to the results previously recorded. The method of performing the measurements remained unchanged; xylenol blue was used to check the determinations made with cresol red in the more alkaline regions—namely, around pH 8.24. The water was tested immediately after being drawn, or within a few hours, unless otherwise stated in the tables.

This paper contains a general account of about forty examples of tumours, mostly “malignant,” found in eighteen species of fishes, all of them marine except two, a Stickleback and a Gold-fish. In all these cases the affection was a very obvious one, attracting immediate attention from the fishermen who caught the specimens, or leading to condemnation of the fish by market inspectors. In some cases the appearance presented by the fish was grotesque, or repulsive in the extreme. I give a list of the specimens dealt with on p. 447–8: all these represent “cancerous” affections. Many other diseased fishes, obtained in the same ways, have been seen and examined. Malformations of development, or growth; large healing scars due to wounds; repulsive ulcers of unknown origin; parasitic tumours and two cases of undoubted piscine tuberculosis (in Cod) have also been examined. Here, however, I refer only to tumours which exhibit the character of malignancy.

In view of the importance of Calanus as a food for fish, and especially for the Herring, its food and feeding habits have been kept under examination throughout the course of the year.

1. Eggs may be clearly differentiated in a female specimen of Haliotis before a length of 2 cm. is reached by the animal, and the female gonad visible before 3 cm. is reached. The female may spawn at 5·5 cm. In the male, active sperms with tails may be differentiated before a length of 3 cm. is attained, and the gonad visible before 4 cm. is reached. The male may spawn at 5·5 cm., if not before.

2. It is estimated that specimens up to about 3·5 cm. long are a year old or less. If so, male and female can both spawn at three years old at any rate, more likely at two years.

3. The first week in August certainly lies within the breeding season. The range of that season is not known, but evidence points to its being late summer.

4. The male gonad is typically white or cream-coloured, or with a tinge of green in addition; rarely salmon or pale yellow. The female gonad varies more, various shades of green, grey-green, brownish grey, etc., are found. These data refer to specimens observed in June and July.

5. Of 127 specimens examined for sex, 50 were males, 71 females, 6 young ones not giving decisive evidence.

6. A male and female were seen spawning. The male puffed out successive clouds of sperms. The female puffed out one cloud of eggs through the holes in the shell, perhaps 10,000 of them. They sank rapidly. They were visible to the naked eye, pale green and quite free from one another. Each was enclosed in a transparent shell.

7. Fertilisation took place after the eggs were laid. The young had reached an early trochophore stage at fourteen to fifteen hours after introduction of sperm. At forty-four to forty-six hours many had left the egg shell and were swimming actively, being then at a decidedly more advanced trochophore stage. How long it is before they settle down and end the larval stage is not known.

8. The food supply consists of algae (both coarse ones and confervas, also diatoms), polyzoa, sponges, small Crustacea, foraminifera, etc. A good deal of sand is taken in with it.

9. Haliotis is certainly a browser and uses the radula as a licking tongue. Experiments were. made to ascertain whether it can extract plankton from the water as part of its food as Crepidula does. The results were interesting (see p. 487), but not conclusive, pointing to inability to use plankton.

10. There is no evidence to show that Haliotis is a homing mollusc like Patella, what there is pointing the other way. It is an exceedingly active species.

11. Haliotis demands the highest possible conditions of aeration in its water. Given these it is hardy, and will even live for months after removal of its shell, secreting one or more new ones (Boutan).

12. In the attempt to find out why Haliotis is getting scarcer in Guernsey and the neighbouring islands (leaving Jersey out of account), it was concluded that this could probably be brought about by overfishing, and by a too ruthless disturbance of the beaches, leading to a certain diminution of the food supply over the area within which Haliotis is available for fishing. If this is not the main cause, some kind of natural fluctuation may account for i t; contamination, natural enemies, etc., not appearing to be main factors. The fishing of Haliotis in Guernsey has consequently been totally suspended by the States for a period of two years. At the end of that time more permanent regulations will be devised.