So large a demand has been made for copies of the recently published paper on the effects of legislation on the crab fisheries of the East Coast that a new paper is necessary. A summary is given of the previous paper and the figures have been reproduced. For convenience of reference they are arranged and numbered as before. The opportunity has been taken to give a review of the attempts to improve the lobster fisheries by legislation.

INTRODUCTION.

1. A series of hauls with the ring-trawl were made at five depths in water 50 metres deep, so that samples were obtained approximately in daylight, at dusk, at midnight, at dawn, and again in daylight.

A depth-recorder was used with the net giving a graphic record of its path through the water.

2. Examination of the catches demonstrated the diurnal changes in vertical distribution of the species caught by the ring-trawl.

3. Four types of behaviour were shown:—

(a) A definite migration to the surface in the dark hours of certain forms living in the deeper layers in the daytime.

(b) An expanding of the distribution of other organisms, that in the daytime had a zone of maximum abundance in the deeper layers, so that they were evenly scattered from the surface downwards.

(c) Certain animals showed no or very little change in their vertical distribution during the dark hours.

(d) A movement up to the midwater region by those forms that during the daytime adopt either a truly benthic existence or are congregated in the water layers immediately adjacent to the sea floor.

(Lists of species grouped under their respective types of behaviour are to be found on page 780.)

4. Many such observations are required before conclusions can be drawn as to the normal diurnal behaviour of plankton animals: this is a definite record of what occurred in this locality in mid-July at a period of full moon in fair weather.

The present paper is a continuation of last year's work on the Euphausiidæ in the neighbourhood of Plymouth (Lebour, 1924), in which the early larval stages were described of Nyctiphanes Couchii, Meganyctiphanes norvegica and, less fully, those of Thysanoessa inermis and T. neglecta. These two last-named forms are reserved for a detailed description in another paper, only Nyctiphanes and Meganyctiphanes being dealt with here. The first paper described these as far as the last Calyptopis stages, and it was shown that they were much alike although perfectly distinct, especially as regards colour. The nauplii and metanauplii were easily distinguishable. The whole of the remaining life-history of Nyctiphanes Couchii has now been elucidated and also that of Meganyctiphanes norvegica, with the exception of a few late larval stages. The absence of these, however, does not materially affect our knowledge of its life-history.

At the end of June, 1924, a female of Typton spongicola, dredged by the Salpa, bearing eggs, was taken from the sponge Desmacidon fruticosus in which it lives, and given to me alive. This was placed in a Plunger Jar in the Laboratory, and on July 8th most of the eggs hatched out. The larvæ did not live long, and never sloughed the skin; but several were preserved, and the following notes on these are of interest, as very little is known of the development in the Pontoniinæ to which subfamily of the Palaemonidee in the Caridea, Typton belongs (Gurney, 1925). The female continued to live for some months at the bottom of the Plunger Jar without any sponge shelter. It ate any dead plankton, and was a useful scavenger. This is interesting, as its ordinary food is the Desmacidon in which it lives (Hunt, 1923).

During the winter of 1924–25 some living specimens of a terrestrial sand-hopper were sent by Major A. A. Dorrien-Smith, D.S.O., Governor of the Isles of Scilly, to Mrs. E. W. Sexton of the Plymouth Laboratory. The specimens, which were handed over to the writer by Mrs. Sexton, have proved on examination to belong to a new species, which is described below and given the name Talitrus dorrieni.

According to information received with the specimens the species has a truly terrestrial habitat: it is found living among the moist humus and under dead leaves in the gardens of Tresco Abbey.

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.

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.

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.

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.

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. In the Lamellibranchs, as typified by Pecten maximus, Mya arenaria and Ensis siliqua, the entire, gut has an acid reaction, the stomach being the most acid region and the pH rising along the mid-gut and rectum.

2. The origin of the acidity of the gut lies in the style. This has a low pH (5·4 in Pecten and Mytilus, 4·6 in Ensis and 4·45 in Mya), and, after it has been artificially extracted from Mya or induced to disappear, by keeping the animals under abnormal conditions, in Mytilus, Tapes and Pecten, the pH of the stomach invariably rises (by as much as 0·825 in Mya and 0·72 in Tapes), although the pH in the mantle cavity has fallen.

3. The style, which dissolves rapidly in alkaline or weakly acid media, is not dissolved in fluids below a certain pH—4·4 for Ensis, 4·2 for Mya, 3·6 for Pecten and Mytilus.

4. The style is never absent, even though animals are starved, so long as they are kept under otherwise healthy conditions. The disappearance of the style under abnormal conditions is probably due to a lowering of the vital activities, which include the secretion of the style substance, and the consequent dissolution of the style by the less acid contents of the stomach.

5. The style is only maintained as a result of a balance between the rate of its secretion and the rate of its dissolution.

6. There is a well-marked correlation between the tolerance of the presence of hydrogen ions possessed by the cilia from the various regions of the gut and the degree of acidity of the fluid with which they are normally surrounded.

7. The pH of the gut in five Gastropods has been investigated. The fore-gut and stomach have invariably the lowest pH.

8. This acidity may be caused by the salivary glands (Patella and Buccinum), the digestive gland (Doris and Aplysia), or the style (Crepidula).

9. The mid-gut and rectum have a high pH, except in Doris, where there is little secretion of mucus, the gut being free and muscular.

10. The style of Orepidula has similar properties to those of the Lamellibranchs. It has a pH of 5·8, and is not dissolved in fluid of pH 3·6 or lower.

11. The cilia from the gut of Buccinum and Doris can function in a pH of 5·0, but there is little difference in the toleration of the various cilia to the presence of hydrogen ions.

1. Putrefaction in sea-water sets free compounds toxic to Calanus. A portion of these compounds withstands oxidation to non-toxic forms in air saturated water for considerable periods.

2. “Deep water” from the English Channel contains a catalyst, probably an iron compound, which increases the rate of oxidation of a number of easily oxidisable organic compounds. Its action is inhibited in surface and inshore waters by dissolved organic matter.

3. Hydrogen peroxide decomposes relatively quickly in “deep water” from the English Channel, at a velocity corresponding to that of a monomolecular reaction. A catalyst, probably an iron compound, active towards hydrogen peroxide, occurs in sea-water. The action of the catalyst is inhibited by dissolved organic substances in surface and inshore water, until such substances are oxidised by the hydrogen peroxide.

1. A simple colorimetric method for plotting the dissociation curve of haemocyanin is indicated. The limits of error are within 5 per cent. The simplicity of the method commends it for laboratory class work.

2. The effect of hydrogen ion concentration on the dissociation of the hsemocyanins of the crustacean Palinurus and the pulmonate Helix have been compared. In the snail change of hydrogen ion concentration over a wide range was not found to affect the dissociation of the hsemocyanin: in 'the crustacean there is a marked effect similar to that seen in the dissociation of hæmoglobin.

3. The similarity of crustacean hsemocyanin to haemoglobin is also seen in that increasing temperature depresses the dissociation curve. The effects of certain salts upon haemocyanin. have also been recorded.

Onchidella celtica (Cuvier) is the only representative of its genus found on our shores. Included in the Sub-order Stylommatophora of the Pulmonates, it is believed to be a land mollusc that has reverted to a marine habitat. It is quite devoid of a shell and closely allied to the land slugs.