The present investigation was undertaken at the invitation of H.M. Treasury, in consequence of an application to the government from H.M. Inspectors of Irish Fisheries for a scientific investigation into the life-history of the mackerel. The problem to the solution of which the inspectors attached particular importance was the relation to one another of the spring and autumn schools of mackerel which regularly visit the Irish coasts. In the spring a multitude of large fish approach the south and west coasts of Ireland to breed. In the autumn schools of immature, but usually well-grown, mackerel come around the island. According to one of the inspectors, the Rev. W. S. Green, there is a sharply defined interval between the two visitations of fish.

The investigation described in the present paper was commenced in 1895, with the aid of a grant of £100 from the Government Grant Committee of the Royal Society to meet the expenses of boat-hire, and a further grant of £25 has been made by the Society to assist in the production of the charts by which the paper is illustrated. The object of the investigation has been to gain an accurate knowledge of the distribution of the fauna on the sea-bottom over a continuous area, i n order to ascertain and where possible to explain the changes which take place in the animal population when the nature of the bottom-deposit changes. At the same time it was hoped that fresh light would be thrown upon the general question of the distribution of life on the sea-bottom and the principles upon which it depends.

The mackerel (Scomber scomber) is a pelagic and migratory fish, which during the warmer months of the year frequents the coastal waters in the northern temperate region of the Atlantic. The whole form of the fish is evidently well fitted for swift motion and the free-swimming mode of life. The spindle-shaped outline of the body, its perfect curves and rounded surfaces, the absence of all irregular projections which would tend to retard forward movement, the great muscular development of the tail, and the deep forking of the caudal fin, combine to produce an almost ideal adaptation for propulsion at high speed through the water.

These notes are intended to be explanatory of the record of tow-net stages of Teleosteans kept by Mr. S. D. Scott and myself. Although my own name appears alone under the title, it must be understood that the observations were in the sole charge of Mr. Scott until the beginning of March. The record of the 5th April is also Mr. Scott's. The rest were kept by myself. The credit of any scientific result that may accrue from the observations previous to the 30th March belongs therefore solely to Mr. Scott, since his notes and figures are so complete as to render my own share of this part of the work a very simple one.

This journal is not designed for the publication of such profusely illustrated papers as are best suited for the explanation of the earliest stages of Teleosteans. It so happens that in the present instance I am able in most cases to refer either to figures already published, or to others now in the press. A series of notes made at Professor Marion's laboratory at Endoûme, Marseilles, was prepared for the press during 1897. Observations made at Plymouth during the same period were found to have an obvious bearing on the subject-matter of my researches at Marseilles, and by the generous permission of Professor Marion I have been allowed to include in a paper shortly to be published in the Annales du Musée de Marseille a number of drawings made from Playmouth specimens. I am therefore able in many instances to eke out somewhat inadequate descriptions by references to figures in the Annales.

The investigations dealt with in this memorandum were commenced in the autumn of 1895, and have been carried on, as opportunity permitted, until July of the present year. The observations were made in 1895 and 1896 by Mr. F. B. Stead, in 1897 by Mr. S. D. Scott and myself, and in 1898 by myself. A preliminary memorandum, dealing with the observations made in 1895, has already been submitted to the Committee by Mr. Stead. As a matter of general convenience it is reprinted as an appendix to this Report.

During my stay, from August to October, 1897, at the Laboratory of the Marine Biological Association of the United Kingdom, I was especially engaged in investigating the variability of Pleuronectes flesus, Linn., and Siphonostoma typhle, Linn. Of the results so obtained, some of more local faunistic importance are briefly reported here.

In the following Memorandum I propose to lay before the Sub-Committee of Enquiry, appointed by the Devon Sea Fisheries Committee, certain facts with regard to the contents of two of the bays on the South Coast of Devon, in which I have conducted trawling experiments, and then to point out the bearing of these facts on the practical questions before the Committee.

During the present year tow-netting has been carried on with such continuity as the weather permitted, and the fish-ova and larvæ thereby obtained have been studied by Mr. S. D. Scott during the winter months, and by myself since the spring. While reserving a general account of the results until the close of the season, it seems advisable to deal now, in however preliminary a manner, with a few species, an addition to the existing knowledge of which may be found of immediate use by workers in the same field. I take this opportunity of expressing my indebtedness to Mr. Scott for observing certain eggs which I was obliged to leave at the Laboratory at a stage too little advanced for specific determination.

This species was originally found by Ehlers at Spiekeroog, an island off the coast of E. Friesland, in the North Sea. It has more recently been found by Joyeux-Laffuie at Luc-sur-Mer (Normandy), and by Prouho at Roscoff and at Banyuls. Its wide distribution, from the North Sea to the Mediterranean, made it almost certain that it would be found in British waters when looked for in the right place. Ehlers discovered it in the substance of the tubes of Terebella (Lanice) conchilega, while Joyeux-Laffuie and Prouho found it in the tubes of Chætopterus.

A Pontobdella lived in my tanks for about six months of the present year. I first placed it in a wide shallow tank with a variety of Actiniæ and a few Hermit Crabs, but no fish of any sort. When first introduced the leech was very restless, and wandered all over the tank. After a day or so, however, he took up his abode on the glass, close to the surface. He remained in this spot about three months, and if disturbed would always go back to it. He never noticed any of the other animals, and did not appear in the least sensitive to the stinging power of the tentacles of the Actiniæ. I have frequently seen him plunge his head and neck in amongst the tentacles of a large Anthea cereus who lived near him, and he treated T. crassicornis with a like disrespect.

So soon as the weather grew warm, the leech displayed signs of uneasiness, and finally left his place on the glass, and retired to a cool corner formed by the slate back and side of the tank, close to the syphons of the aerating apparatus, where he remained two months and a half.

He never appeared to notice sticks or nets moving near him in the water, but would remain in his usual position, viz., the base fixed to the wall of the tank, the body sticking out horizontally for about half its length, and the fore part doubled under, so that the mouth was pressed against the under side.

I have made several attempts to keep medusae alive in an aquarium, but have only recently been successful. A medusae when first placed in an aquarium swims actively about, but in a few hours it sinks to the bottom apparently tired out. After an interval of rest it takes another swim and again sinks to the bottom. This is repeated until the medusa becomes completely exhausted; then it stays at the bottom and slowly dies. In spite of every attention, plenty of clean sea-water, plenty of copepods, and a suitable temperature, I found that my medusae often used to die within a day of their capture.

When I have been watching medusae at the surface of the sea, I have noticed that they simply float along with the tide without often pulsating the umberlla. In my bell-jars the water was perfectly motionless, so that a medusa had to pulsate its umbrella in order to keep afloat, and as soon as the pulsations stopped it began to sink. There are some species, like those belonging to the Bougainvillidae, which live longer in confinement, as they are able to poise themselves in the water by the extension of their tentacles and remain motionless for long periods, but even these finally reach the bottom of the bell-jar, and a long period at the bottom ends in death.

It appeared to me that to keep medusae alive in an aquarium it was necessary to have the water in motion so that a medusae could float about just as it does in the sea, without having constantly to pulsate its umbrella.

During my visit to the Plymouth Laboratory in September, 1895, Mr. Roach brought in, on the 28th, some fine colonies of Tubularia which he had found attached to the stern of a large three-masted sailing ship, the Ballachulish, of Ardrossan. This ship had come direct from Iquique, Peru, and after staying a few days in the Sound left for London. The Tubularia was kindly given to me for identification by Mr. E. J. Allen. After making drawings and noting the variation of the different organs, I came finally to the conclusion that as it agreed so closely with Parypha crocea, Agassiz, from Boston Harbour, there was no need to add another species to the genus. I was fortunate to meet with colonies of both sexes, and to find the ova in various stages of development. I believe enough material has been preserved to trace the development of the ovum, which shows a remarkable similarity to the development of the ova from the medusa of Hybocodon prolifer.

Actinulæ were being liberated in large quantities when the colonies were taken from the ship, so it is possible that this hydroid may become an interesting addition to the fauna of Plymouth Sound.

To distinguish this species it is necessary to examine the female gonophores, and count the number of apical ridges. Agassiz states that the number varies between six and ten, but only eight were present in my specimens. The male gonophore is destitute of ridges, and usually terminates in a blunt apex.

Morone labrax. Linn. Bass.

Towards the end of May a large female bass in one of the Aquarium tanks appeared to be approaching ripeness, and constantly swam round the tank followed by one or more of its companions, probably of the opposite sex. A fine-meshed net was accordingly placed over the overflow from the tank in question, and on the morning of the 29th May was found to contain a very large number of eggs, undoubtedly attributable to this species, the only other Teleostean inmates being turbot, congers, pollack, rocklings, and two species of wrasse.

All the eggs proved to be unfertilised, or, at most, showed only an approach to segmentation, which may have been due to the spermatozoa of a rockling. Circumstances seemed strongly to point to the fact that the eggs are not all shed at once, but owing to an unfortunate series of accidents with the net it is impossible to speak on this point with absolute certainty.

Although the bass is a common British fish, its ova find no place in the records of British naturalists, and are only known from the descriptions of Raffaele, who obtained them both from parents living in the tanks of the Naples Laboratory and from the neighbouring sea.

The eggs observed by us at Plymouth are spherical, and, while living but unfertilised, measure from 1·25 to 1·34 mm in diameter. Raffaele gives 1·155 to 1·2 mm as the diameter of Naples examples. The latter have an oil-globule of ·332 to ·366 mm.

For a number of years our tanks have from time to time contained a very large and easily-recognised Skate-purse, but its specific identity has remained a matter of uncertainty. Fishermen attributed it to the “Bottle-nose ray”, a species not to be found, so far as I am aware, in ichthyological works.

Scandinavia has been for a number of years past the centre of interest in hydrographic inquiries. The waters of the Baltic, Skagerack, and Cattegat, have been thoroughly investigated by Swedish men of science; the complicated currents of those seas and their periodic alterations have been determined and explained; and a relation has been found to exist between the movements of herring and mackerel and the periodic changes in the character of the water which bathes the Swedish shores. The brilliant results attained by the Swedish hydrographers have been fully described by Prof. Otto Pettersson in the tenth volume of the Scottish Geographical Magazine (1894), and a critical summary of these results is included in Cunningham's paper on the “Physical and Biological Conditions of the North Sea,” published in this journal last year. (Vol. iv., 1896, p. 233.)