Comparison of the conceptions which have hitherto been held in regard to the hydrography of the English Channel with those which are offered as a result of the recent activities of the Atlantic Slope Committee, shows that a difference exists which, in the writer's opinion, lies in the interpretation of the material, rather than in the fundamental differences in the material itself. For example, it is stated that the physical character of the water in the English Channel is conditioned, especially in the summer months, by that of the North Sea water rather than by that of the Atlantic water. “En plein été, en août, les eaux chaudes de la mer du Nord affluent dans la Manche.” A similar regimen is suggested for the waters of the Irish Sea, which are said to be derived from the northward. Carruthers shows that the normal water movement in the eastern part of the English Channel is through Dover Straits into the Southern Bight, this movement appearing to be more persistent along the bottom than on the surface. Furthermore, one of the two months in which reversal of this direction appears least likely to occur is August.

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.

When studying the seasonal changes in the algal plankton in relation to the supply of the constituents necessary for their growth, one is led to seek the source of the silica used to form the valves of the diatoms and to consider whether lack of silica might be a factor limiting their multiplication.

Although adult Norway lobsters are extremely common on the southern part of the Northumberland coast, there were no records of the taking of larvæ of the species in this part of the North Sea until the Plankton Investigation now being carried out at Cullercoats (1) was commenced.

During the period 1921–23 a few specimens were taken from time to time in the ordinary plankton hauls, but the best catches of Nephrops larvæ were obtained from the young fish trawl used at a number of stations in 1922 arid 1923. It is, therefore, chiefly on the material from the last two years' samples that the following observations are based.

All three of the larval stages have been obtained, together with a single post-larva, but the majority of our specimens are second and third stage larvæ.

While experimenting on the vertical distribution of plankton in comparatively shallow waters I found it necessary to devise a releasing apparatus for use with horizontally towed plankton nets. Under existing working conditions there were four circumstances for which the instrument had to be adapted:

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.

It is a curious fact that the majority of the British anemones had been discovered by 1860, and that half of them, as listed at that date, had been established during a burst of energy on the part of Gosse and his collecting friends. Gosse added 28 species to the British Fauna himself. It is still more surprising that since Gosse ceased work, no authentic new ones have been added, other than more or less offshore forms, with the exception of Sagartia lucice; and this species appears to have been imported from abroad. There is, however, an anemone which occurs on the Breakwater and Pier at Plymouth, which has not yet been described. Dr. Allen tells me it has been on the Breakwater as long as he can remember, and to him I am indebted for the details of its habitat given further on. Whether it occurs elsewhere than in the Plymouth district and has been seen but mistaken for the young of Metridium dianthus, is as yet unknown.

In a former paper (1922) it was shown that the pH value of stored sea water decreased owing to the production of carbonic acid by organisms in it, and the oxidisable matter as indicated by this biological method appeared to be higher than the result obtained by oxidation with permanganate, according to various analyses available for comparison. These, however, were not done on the same water, so an attempt was made to determine this quantity on water of the English Channel off Plymouth. As is well known the permanganate method gives results which vary appreciably, according to the conditions of the experiment.

From May, 1922, onwards the sq. metre bottom-sampler has been used to collect samples of the bottom-deposits with their animals, in the waters off Plymouth. The animals have been removed as soon as possible after capture by passing the samples through a series of sieves, and have been preserved in alcohol, to be identified and counted ashore. The present report deals with the distribution of the species represented, in the light of Petersen's Community investigations in Danish waters.

I express my thanks to Dr. Allen, Dr. Orton, Mr. Hunt, and Mr. Smith, of the Plymouth Laboratory, for their kind help in the identification of the material. I am particularly indebted to my friend, Mr. R. Winckworth, a late member of the staff, who has not only gone over with me the bulk of my collection of lamellibranchs, but has provided me with an excellent type series as complete as the material would allow.

The extensive use of his bottom-sampler in Danish waters and elsewhere has enabled Dr. C. G. Joh. Petersen to advance an opinion that “as a rule it is best to regard the animals living on the sea-bottom as communities, just as botanists group together the vegetation of the land into plant communities, even though in the present state of our knowledge it is impossible to show how intimate the mutual relations are between the animals of the sea in the single cases.”

It will probably assist the reader if I commence with a short summary recalling the more important points, concerning the recognition of communities, which have been advanced by Peterson, and in doing so I shall adhere closely to his own words.

This paper contains anatomical descriptions of some British species whose systematic position has hitherto been uncertain because of the absence of detailed knowledge of their structure. To these descriptions are added notes on anatomical points of interest connected with other species.

Some of the facts gained have a general systematic bearing which will be pointed out as they occur in connection with the descriptions, or in the discussion at the end of the paper. I am indebted to Dr. Allen, Mr. W. Edgar Evans, Mr. E. Elmhirst, Miss M. Delap, and Dr. T. A. Stephenson for material, and to Dr. Esdaile for valuable guidance.

Since April, 1921, observations of temperature and salinity have been made at depths from top to bottom of the sea at Station El, 20 miles to the south-west of Plymouth, where the depth is 70 metres. These observations already throw some light on the causes of different sea temperatures during the same month in different years. As these temperature differences from year to year play an all-important part in the life of cold-blooded marine animals (1), it is of particular interest not only to follow their seasonal changes, but to arrive as far as possible at the causes which govern them.

Changes in salinity and the temperature conditions during 1921 showed a marked inflow of warm highly saline Atlantic water into the English Channel, and a very marked inflow into the El area during September, October and November of that year (2). From that time until the end of 1923 there has been an irregular fall in salinity of the water at El.

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 a previous paper (1924) the writer considered the factors which bring about the mixing of surface water, warmed by the sun, with the cooler water below. Observations were cited to show that in the English Channel, between May and September, a warm surface layer may exist, which differs from the deeper water in being more alkaline and poorer in phosphates; both these differences are due to the activity of the phyto-plankton. The reduction in phosphate proceeds in the upper well-illuminated layer till none is left. No further increase in phytoplankton is then possible till phosphate is set free by decomposition or supplied by mixing with the deeper water. The phenomena of thermal stratification are consequently of great importance in the study of the phyto-plankton.

In 1913 a successful attempt was made to introduce the European Turbot to New Zealand waters. On 12 January of that year 298 young fish, caught in the neighbourhood of Plymouth, and kept for some time at the Marine Biological Station, were put aboard the Waimana. Of these fish 195 were safely transported across the tropics, and were put into the tanks at the Portobello Marine Hatchery. The operation was a very successful one, thanks to the care of the late T. Anderton, who was then Curator of the hatchery.

The turbot were originally from one to two inches in length. It was intended to liberate most of them in the sea, but, on consideration, it was decided to keep them in captivity. Three years later (May, 1916) there were still 182 fish, 5 having died and 8 having been liberated in the sea. They grew very rapidly in the tanks, so much so that in May of 1916 many were about 18 inches in length. To keep these large fish healthy was difficult, and so, in 1916, 128 of them were liberated in Taukutu Bay.

Data obtained during the cruises of the s.ss. Huxley and Oithona in the years 1903 to 1906 indicated a general seasonal movement of water into and out of the mouth of the English Channel. It was found that in the autumn, somewhat sooner or later and to a greater or less extent each year, water, of the high salt content characteristic of the open Atlantic in the north of the Bay of Biscay and to the south-west of the English Channel, began to move in a north-easterly direction into the mouth of the English Channel, extending in a tongue along the centre of the Channel and into the Irish Channel, which is characterised by water of lesser salt content.

This general movement of relatively high salinity water continued during the winter until the spring or early summer, when water of lesser salinity moved southward from the Irish Channel across the mouth past Ushant, and to some extent into the English Channel; the condition in August being that water of relatively high salinity which had entered the Channel during the winter months was cut off from Atlantic water of equal salinity by a less saline water-mass extending south from the Irish Channel.

These general movements have been deduced from the data collected during the cruises in February, May, August, and November. To accurately depict the changing conditions and follow the movement of the water year by year would require frequent observations, more or less simultaneous, over a wide area—a condition of perfection which in practice could not be obtained without the use of several ships working almost continuously and in conjunction.

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.

The short investigation here described was made in March and April, 1922, during the spring mackerel fishing season off the Cornish coast, in order to discover whether the opinion of Skipper Wylie, of Lowestoft, (drifter, Realize) was justified. In his opinion the best catches of mackerel were made wherever his thermometer showed him a sea surface temperature higher than that of the neighbouring water.

About a dozen drifter skippers, who volunteered to undertake the work, were given thermometers, graduated in ⅕° C. (about 20 graduations per cm.) and forms upon which to record their observations, and were shown how to take a surface sample and read its temperature. These thermometers were not very suitable, since the range was too great, and therefore the scale too small. They also suffered from the defect that the mercury thread easily become broken, and if the detached portion ran down into the bulb at the top of the tube, it was difficult to ensure that all the mercury came out again, and that the thread made a proper joint.

The forms used (p. 241) were based upon the log books used during the investigations on pelagic fishes from 1895 to 1911* (Russell, 1915). It was hoped that sufficient data would be collected in the course of a month, but, although the experiment was extended into April, only 32 records are available, covering the period 9th March-19th April.

These records are tabulated in Table 1. In those cases where the temperatures at the times of shooting and hauling differed, both the values are given, but their mean has been used in computing averages.

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.

A luminous organ of a hitherto undescribed type has been found in a Macrurid fish. This organ is described in the present paper. It consists essentially of an epithelium for the secretion of luminous substance, which has been thrown into long folds and wholly invaginated to form a gland. This gland is bound in connective tissue and has a compact appearance, and is furnished with supporting tissue internally. The duct is a flat and wide passage, continuous with the gland, which opens to the exterior about the anus in such a way as to surround the lower part of the rectum. The gland lies in the thickness of the body-wall forward of the rectum and between and behind the pelvic fins.

The nature of the secretion is discussed and some experiments described. The luminescence appears to be due not to bacteria living as guests within the tissues of the fish, as has been shown for other species, but is essentially due to the well-known reaction wherein a substance luciferin is burnt to oxyluciferin in presence of the ferment luciferase, with emission of cold light.

1. The seasonal changes in the sea water of the English Channel and. of Plymouth Sound have now been followed for almost two years, and the second year's results closely resemble those of the first, and again confirm the earlier surface results obtained by Matthews. For 1923 the average consumption at Station El, surface to bottom, 70 metres, was 29·6 mg. of P2O5 per cubic metre, leaving a balance of 7·4 mg. out of the original 37 mg. For 1924 the corresponding figures were, used up 28·3 mg., balance 8·7 mg., winter concentration 37 mg. The minimum average value was obtained in June and July in 1924, in July only in 1923. During June, July, and August, 1924, the surface water was almost entirely denuded of phosphate, values from 1·5 to 2·5 mg. per cubic metre being obtained. These figures would be milligrams per metric ton if fresh water were being considered, as it is they are milligrams per 1027 kg. for. water of S35·3% at 11°C, so it may be appreciated that very little phosphate remains unutilized by the phytoplankton.

2. Owing probably to the high sunshine record for March the year 1924 was over a month ahead of 1923 in the spring as regards phosphate consumption, and, therefore, it may be presumed in the multiplication of the phytoplankton. At the same time, in the attainment of definite temperatures 1924 lagged about a month behind. 1923 in spring. Since temperature has such a marked effect upon the rate of development of the plankton as a whole it appears that the zooplankton must have been retarded in 1924 as compared with 1923.

3. Samples obtained from the tropics show that even in winter phosphate may be much diminished, for the light is bright. The periodic alterations in phosphate content are, therefore, suppressed or much reduced as compared with the temperature zones. It is indicated that in arctic latitudes the sea becomes even richer in phosphate during winter than it does here, accordingly the summer development of phytoplankton is all the. more abundant.