Hitherto rearing and "fattening" has been a far less dubious enterprise than breeding, but recent discoveries point to a possible change in this respect. For a considerable number of years salmon have in this and other countries been systematically "hatched" from ova, artificially fecundated; and as method and manipulation have improved, it has been found that most of the fishes of commerce—both sea and fresh-water—can in like manner be multiplied at the will and under the control of man. Obviously a great step in advance would be made if oyster-culture could be so widened in scope as to include artificial propagation. The reproductive power of the oyster is very great. It is estimated that the larvae sent forth by a single parent oyster at a single breeding period reach in number a million or more. If this enormous reproductive power could be fully utilised there would be no scarcity, but, on the contrary, a too abundant supply. But only a very small proportion of the young oysters come to maturity, or become "fixed" where they can live. The difficulty is not in obtaining oyster larvae, but in the fixation of the spat. The larvae swim about in the water for a brief period of not very many days, the exact number being undetermined and perhaps variable. At the termination of its free-swimming career the young oyster settles down to the bottom of the water, there to pass the rest of its life. It alights, probably on the first solid object that comes in its path, generally the sea-floor. Should it have the good fortune to fall on a suitable object, its chief risk is that of being devoured by some other animal. In the vast majority of cases, however, the larvae are swept away by currents to be lost on unsuitable soil— choked or buried perhaps by sand or mud. To intercept these larvae or spat by means of faggots or branches of trees, tiles, or prepared wooden collectors, or even stones, or to lay down a culch or top-dressing of clean empty shells, where they are expected to fall, are familiar operations of oyster-culture. By these contrivances a certain proportion of the young oysters are, when other circumstances are favourable, preserved; but probably a far larger proportion are carried away by currents to stock new or replenish old banks, or perish, as the case may be. Uniformity of method does not prevail among British cultivators, but there has been an all but complete identity of experience among them in one respect. They have generally been unable to maintain their fisheries in a prosperous condition by means of natural increase. Spat either has not been produced, or it has perished from cold, or at least failed to adhere to the collectors prepared for its reception. The best localities for reproduction are situated in the English Channel, chiefly about the Isle of Wight; and the reason of their superiority, it seems pretty clear, is that the temperature is higher there at the breeding season than in the North Sea. A temperature approaching 70° is favourable to the fixation of spat, and while this is higher than the normal range of the waters of the Channel in early summer—the spatting time—it is still farther above the temperature of the Thames estuary and the east coast of these islands. The Channel receives a branch of the warm Gulf Stream, and responds more quickly than the colder North Sea to the warming rays of the summer sun. I have learned—though information of the kind is not an abundant commodity—that at some at least of the Channel oyster farms there have been exceptionally good falls of spat during the last two seasons, and that on the east coast it has also been better than the average. A very good spatting season in the Thames is quite phenomenal, and 1859 continues to stand out as the year of proverbial excellence in regard to the supply of young oysters. In the warmer waters of France considerable vicissitudes of fortune attend the oyster breeder's industry; but there such a thing as absolute failure is hardly known, whereas in these more northern latitudes it is by no means of rare occurrence. Still we have the important fact to remember that the oyster is indigenous all round these islands where localities that suit its habits are to be found; and the oyster industry has of late years undergone a great development in the estuary of the Scheldt, while it holds its ground in the cool waters of the Schleswig-Holstein coast—showing that the temperatures prevailing in these latitudes are not fatal to reproduction and development on a moderate scale, though it may perhaps be impossible to get the plethoric swarms of young that are successfully collected farther south in favourable seasons.

It is of great importance that the culch or collectors should be perfectly clean, and not covered with vegetable matter of any sort; in other words, they should not be put down until the reproductive season is close at hand. Wooden and even tile collectors should be covered over with a coating of hydraulic lime, or asphalt and sand, before being put down; and a culch of old shells, if previously used, should be bleached in the sun before being put down a second time, so that any kind of organic matter that may adhere to them may be rendered incapable of life and growth when they are put back into the water.

Another point connected with the reproductive process has likewise an all-important practical significance. The nature of that process has not been adequately explained as yet; but according to eminent physiologists, such as M. Davaine, Professor Huxley, and Professor Hoek of Leyden, it is clearly established that the same individual oyster (O. edulis) is alternately male and female, the milt being secreted in abundance after the ova are extruded, and ova in like abundance after the extrusion of the milt; but at any particular breeding time each oyster, as regards reproductive efficiency, is either exclusively male or exclusively female. As the ova in this species of oyster undergo incubation between the gill-plates and between the folds of the mantle, it is obvious that they must be fertilised there, and if the physiologists are right the fertilisation must take place from without. This can occur only in one way. When the milt is fully matured it must be shed into the sea as in the case of fishes, and must reach adjacent oysters and come into contact with the slimy mucus in which the ova are imbedded. This must occur some little time before the female is unburdened of her brood, and manifestly there must be a great deal of waste, while an incredible number of spermatozoa must reach the ovaries if anything like full effect is to be given to the reproductive power of the female. And in proportion as the oysters on a bank are distant from each other are the chances of fertilisation lessened. A few oysters, in close proximity to each other, might soon, in favourable circumstances, replenish a whole bank, but when the dredge has done its worst and only a few stragglers remain, the work of destruction is complete, and another is added to the long list of exhausted beds. If the industry is to thrive, careful attention must, therefore, be given to the conditions governing the reproductive process, and especially to the most essential condition that a sufficient breeding stock should be left gregariously crowded together in accordance with the plan of nature. In France this has been recognised for a considerable number of years, and the Government insists on reserving a portion of the natural beds exclusively for breeding purposes, only allowing a little dredging in order to clean the ground and clear away enemies at intervals. From these natural banks the larvae spread all over the neighbouring waters, and myriads fix on the collectors laid down on private grounds for their reception. Of late years there has been, as already said, a great revival of the Dutch oyster fishery of the Scheldt—due exclusively to the abundant collection of spat on particular parts of the Yerseke bed. This revival at first caused some surprise, and nobody knew very well how to account for it. Various parts of the bank were dredged for the purpose of ascertaining the source of the spat, but only with negative results. At last some one thought of the fringe of 500 metres from the dykes by which the country is protected from the inroads of the sea. Within this fringe dredging is prohibited, and is besides rendered almost impracticable by the presence of large stones. Divers were sent down to explore the ground, with the result that almost everywhere the stone-works which jut out from the dykes were found to be covered with oysters that had never been disturbed. These natural beds were undoubtedly the explanation of the great abundance of spat in regions some little distance off, but found by actual experiment to be connected with them by currents. It may be added that the portion of the Scheldt in which these beds are situated has been cut off by a railway embankment from all direct connection with the freshwater stream, and is to all intents and purposes a sheltered bay or creek filled with the waters of the sea.

An analogous order of things is observed at some of the principal seats of oyster cultivation in the east and south of England. The Blackwater, in Essex, is a wide estuary or arm of the sea, and though many of its oyster-grounds are public and frequented by large numbers of dredgers, they nevertheless maintain their productiveness. The reason is that they are every year replenished by spat brought down by currents from the well-stored private grounds in the upper creeks and reaches of the estuary. These private layings are stocked with young oysters from the public grounds lower down; and thus a mutually beneficial reciprocity exists, and the industry is successfully carried on from year to year. In the same district, a similar condition of mutual dependence is observed on the Roach River, the upper portion being carefully stocked as an oyster farm, while lower down much of the bed is, before the breeding season, strewn over with culch for the reception of spat. And off Whitstable the public grounds undoubtedly benefit by the well-stocked fattening grounds of the bay; but as the water is here an open expanse, unconfined by banks, very much of the spat is dissipated and lost, while experience also proves that the best fattening places are not the best breeding places. The best brood oysters are the produce of natural banks, though artificial layings also yield satisfactory supplies in average seasons, and in localities favourable to collection.

These facts, and were it necessary they might be multiplied., tell us somewhat of the conditions that must be observed if a large oyster-industry is to be developed in Scotland. With regard to breeding, the best practical measure that can be adopted, is to conserve with jealous vigilance every existing natural bank. It is very difficult to create a good breeding place, but not quite so difficult to utilise to its utmost a breed-jug place already in existence. This utilisation is to be effected by restricting, or altogether preventing, the removal of breeding stock, by clearing away occasionally the whelks, starfishes, boring-sponges, and other "enemies" by which the banks are apt to be infested, and by adopting measures for the collection of as much as possible of the spat. The work of "cleaning" is done by means of the dredge. Collection of spat must be preceded by experiments or observations to ascertain, as far as possible, where the spat is likely to fall; and except in waters more or less hemmed in by land, there is not, it must be confessed, much hope of succeeding with this branch of the business.

In American and Portuguese oysters (O. virginiana, O. angulata) the process of embryonic development is effected not within the shells of the parent, but, as in the case of most fishes, in the water of the surrounding sea. The ova are cast into the water, and are there fertilised, and there the larvae come forth as free-swimming creatures. With these oysters some progress has been made towards establishing artificial propagation corresponding to the fundamental operation of fish-culture, as now extensively practised in Europe and America. The pioneer in this art was Dr W. K. Brooks of Baltimore, director of the Chesapeake Zoological Laboratory, and chairman of the Maryland Oyster Commission; and other early labourers in the same field have been Professor Pice and Mr Ryder in America, and M. Bouchon-Brandely in France. Dr Brooks's experiments in 1879 were witnessed by Lieut. Winslow, of the United States Navy, who, being stationed next year at Cadiz, repeated them with the Portuguese oyster, which he found to be likewise capable of artificial propagation. Stimulated also by Dr Brooks's experiments, M. Bouchon-Brandely has for some years been carrying on an important series of researches with the Portuguese oyster, and has succeeded in raising a large number of young from artificially fecundated ova through all the early stages, as is fully detailed in his Reports to the French Government, which have been translated and issued by the Board of Trade in this country. The practicability of raising Portuguese and American oysters—which indeed are one species—from artificially fertilised eggs, is therefore clearly established. It is true that these oysters differ not a little from the Ostrea edulis, and are in by no means so high repute; still they have a good commercial value, and their cultivation artificially from the earliest stage is an important step in advance. As regards the common oyster, which is incubated within the shells, the difficulty is not in obtaining larvae, but in getting the spat to adhere to the collectors or culch. In confined waters, food conditions and want of aeration are difficulties as well as temperature ; and whatever reasonable hopes there may be that these difficulties will sooner or later be overcome, we must for the present rely upon the old methods, and look forward with hope to the progress of experiment and research into the conditions of oyster life. The requisite aeration of confined water can be provided by mechanical means ; but food conditions are more unmanageable, because, for one thing, they are less perfectly known. They are no doubt affected by aeration, and probably also by temperature. The temperature of a sea water tank of moderate dimensions can of course be raised by artificial means, but the art of cultivating the microscopic organisms, upon which the oyster feeds and fattens and its larvae are sustained, has still to be learned. Old oysters are sometimes supplied with a sprinkling of oatmeal, and appear to benefit by imbibing particles of this food, but we have still to learn how to provide the natural food of the larvae, or whether any substitute is available. These speculations, however, pertain to the scientific branch of the subject. The life history of the oyster is still known only in part, and we are but on the threshold of the art of propagating this mollusc through the intervention of human contrivance. Within certain narrow limits we can assist nature. We can also refrain from thwarting nature by dredging away the parent stock, instead of leaving sufficient breeding places intact.

As a practical means of developing the oyster fisheries of Scotland, we must, I think, look first to an extension of the system of granting leases of oyster grounds for short terms, on condition of a certain amount of money being annually expended on their cultivation. The proceedings to this end, though they might with advantage be further simplified, have been facilitated by the Sea Fishery Act for 1885. Having found a promising locality, and obtained a lease from the Secretary for Scotland, on the recommendation of the Fishery Board, the grantee would set about preparing the ground, putting up a rough fence, perhaps, to mark it off and afford some protection, or at least surrounding it with a few stout posts to which brushwood or hurdling might be attached, at the proper season, for the collection of spat. If the nature of the ground permitted, or rendered it desirable, sloping ridges might be formed so as to give the allotment more or less of an undulating surface, as is done on many of the American oyster layings of Chesapeake Bay; and it should also be strewn over with a layer of old shells, or if these cannot be procured the smaller debris from a stone quarry would be a fairly good substitute. At sundry places on the Adriatic it is customary to drive branches of oak into the bed of the sea round oyster grounds, in 1½ fathom of water, every spring; and in the autumn these branches, which meanwhile have become laden with young oysters, are transferred with their burden into deeper water. There the branches are sunk, and the oysters left to develop and mature—safe alike from the heat of summer and the frosts of winter. At other Adriatic stations the branches, instead of being staked, are simply laid down in the water. This, it may be added, is substantially the method of oyster-culture pursued at Lake Fusaro on the Gulf of Taranto, since the old Roman days—the breeding oysters being placed on heaps of stone with wooden stakes or piles planted around them. It is to an examination of this method by M. Coste that the modern development of the French oyster industry is in great measure due. On M. Coste's recommendation, the Fusaro system was introduced at different points on the Bay of Biscay, and its adoption soon became general. About the same time, however, the system of artificial parcs and claires had its inception. The parcs are simply portions of the foreshore walled round roughly with stones, and having a clay foundation, which retains water, are strewn with a covering of stones or shells. These pares are covered by the sea at every tide, and much labour is expended in keeping them in good order, and in clearing away intruding marine animals. They are used as stores and breeding places, and at the breeding season, collectors—generally tiles— are laid down in them. The claires are similar ponds, but, beyond the range of the ordinary ebb and flow of the tide, though reached by the high water of spring tides. They are used for fattening and "greening" oysters, the comparative stagnation of the water being favourable, as would seem, to the growth of the microscopic organisms by which these processes are effected. Much, however, depends on the character of the soil; British "natives" are not the sickly produce of stale ponds.

The sensitiveness of the oyster to frost renders the French system unsuitable to Scotch conditions, and the model for Scotland is rather the old Italian system. But with a view to commercial results, attention will naturally be directed to rearing fully as much as to breeding. Supplies of brood, ready for "planting out," can be procured at Auray or Arcachon, at a price that need not be regarded as prohibitive. To some people it may sound like rank heresy, but I must also mention the American oyster as deserving of notice. Large numbers of the kind known as "East Rivers," which are those most in repute in this country, are imported every year at the young stage, and "planted out" in the Conway, the Menai Strait, and, I understand, certain places in the south of England. The American oyster trade seems to prosper in this country; at all events, the Transatlantic bivalve is gaining for itself every year a more and more important place in the English market. The most noteworthy trait in its character is, that while it grows and thrives in British waters, it does not reproduce itself; and thus the grounds as they are cleared have always to be replenished by new importations of young from America, Whether "natives," or Americans, or Portuguese are dealt with, the beds where they are to winter must be protected by having always a few feet of water over them. Four feet is a sufficient minimum in sheltered localities, but where the beds are more or less in the current of a river, a greater depth than this is necessary. To attempt to raise oysters on a sandy beach would be no less absurd than to attempt wheat growing among the moving sands of the Sahara. Soft mud is equally to be avoided. A somewhat firm alluvial or clayey soil, with a certain admixture of calcareous matter in some form, is a general description applicable to very many oyster beds; and there must be a good deal of organic matter on the ground or in its neighbourhood. Rocky localities, though not always unsuitable to oyster growth, are undesirable on account of the difficulty of dealing with them. To enlarge and improve existing beds, I repeat, is a far more certain way of attaining success than to attempt to establish new ones. The usual method of taking up oysters is by the use of the dredge, but in America the "tongs" is employed, and in moderately shallow water it is preferable for ridged grounds, as causing less disturbance.