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The first requisite now is a supply of pure spring water for hatching the eggs,-neither too warm nor too cold. From 45° to 500 is the best. Every degree warmer or colder will make from six to eight days difference in the time of hatching. From 37° to 54° is considered the limit within which to hatch trout. By a calculation in Mr. Norris' book ("American Fish Culture"), it will take one hundred and sixty-five days with water at 37°, and thirty-two days with water at 54o.

The hatching house in the establishment we have spoken of is a wooden building twenty feet long by twelve feet

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wide, into which water is admitted about three feet above the level of the floor, from springs immediately in the rear, enclosed in sunken tanks as before described, and covered so as to be out of reach of cold or heat. To enable the water to be brought in at this height from the floor, the house is sunk three feet in the ground, and the boards are covered with a heavy coat of pitch inside and out, to a point above the level of the surrounding ground to prevent their rotting. The amount of water now used in the house is what will flow through two faucets, one inch in diameter, with a moderate pressure.

This is led in the first instance into a straining trough (Fig. 40, a), running across the width of the building, where it passes through flannel strainers (1) to insure its purity. It then flows into a distributing trough

R (6), which is parallel to the straining trough and a few inches lower, from which, by means of faucets, it is let on to the hatching troughs in such quantity as may be best.

The hatching troughs (Fig. 40, c) are placed at right angles to the others, and are sixteen feet long, fifteen inches wide, and eight inches deep, and are six in number with covers upon hinges, the top of them being about fifteen inches from the floor. They are lined with slate, one-half of an inch thick, upon the sides and bottom, with transverse subdivisions; every two feet made of the same material and two inches in height. A fungus growth, very detrimental to the ova, is unavoidable when wood only is used. The bottom of the troughs is covered with about one inch of moderately fine gravel, and over it flows a constant stream of screened spring water about an inch deep, the lower end of the trough being depressed two inches. On this gravel the impregnated ova are placed in a single layer. In about three weeks the eyes can be seen in the impregnated eggs, appearing simply as two black specks; the blood vessels of the future fish may also be seen, and from this time its development may be traced daily in the shell. With the temperature of the water at 48°, we may look for the hatching of the ova from the forty-fifth to the fiftieth day. A trout just hatched is about three-eighths of an inch in length, and has attached to it an umbilical sac of several times its own bulk, which sustains the young fish for about forty days, when it is absorbed. The young fish may now be let out into the waters it is desired to stock. They will thrive if placed in a brook even at this early age, such waters supplying an abundance of minute particles of food. If reared in confinement, however, they must be fed with raw liver chopped to the consistency of blood and mixed with water, with the yolk of eggs grated very fine and treated in the same way, or thin sour curds. The latter food is perhaps the best as it sinks more slowly, and trout seize their food in transitu, paying little attention to it after it reaches the bottom.

We have sought only to give such a general description of a fish breeding establishment, and of the habits and treatment of the fish, as would give some idea of the practical parts of the art of pisciculture. There are many details connected with the subject which we have not touched upon. They can be found very thoroughly treated of in any of the modern works on pisciculture, of which Norris' "American Fish Culture" is the latest and most practical.

In the above all general considerations have been avoided. It would, perhaps, have been as well to have stated that the arguments in favor of artificial hatching of eggs is based on the small proportion of them that are hatched when deposited in a stream, by the fish following the course of nature, and the very large proportion when hatched by artificial arrangement. The many enemies of fish spawn (other fish, water insects, birds, rats, not to speak of sediment, freshets, ice, etc., etc.) reduce the number of the eggs sadly. It has been calculated by English pisciculturalists that not one salmon reaches the proper size for the table out of every thousand eggs deposited in the stream. As the salmon migrates to the sea when weighing only a few ounces, it would, however, be more subject to casualty than the trout.

THE FRESH-WATER AQUARIUM.

BY C. B. BRIGHAM.

(Continued from page 136.) We have seen that the aquarium is to be distinguished from the common fish-globe by its self-supporting character. We have examined in a general way the philosophy of the aquarium and concluded that the rectangular tank was the most useful one to have. Let us now look for a situation for the tank before the specimens are placed within it. It is desirable that the sun should shine upon the tank for at least an hour during the day; an eastern or southern aspect then is the best for this purpose. This is especially true in the winter time, while in summer a northern aspect would be preferred, as the water in the aquarium is apt to be overheated by the sun during the hot months. One trouble which arises from too much sun is this : that the small green plants of conferva grow very rapidly upon the glass and stones, obstructing the view of the inside of the tank, and rendering the stones very hard to clean when taken out. These confervæ do not injure the water at all; they even give out oxygen as other plants, and it seems as if it were a provision of nature, that they should render the glass opaque so as to protect the inmates of the tank from injury. This confervoid growth is not essential to the welfare of the tank if it is properly stocked with other plants, and it is desirable to have as little as possible of it. To effect this, a wide screen, or a simple sheet of brown paper, so placed as to shut out the sunlight from the tank will answer the purpose; or by pulling the window shade down when the sun shines upon the tank; or, what is best, by placing a row of plants with full foliage between the tank and the window, we have other means of obviating the difficulty.

Whether the sun shines upon the tank or not, a fresh-water aquarium should have all the daylight it can get, both for its own welfare and for our own convenience in examination. I am convinced that this is correct from my own experience, although Mr. Hibberd, a good authority on aquarial matters, says to the contrary : "A full flood of daylight is more harm than good, a frequency of sunshine destructive, and the tenants of an aquarium are seen to better advantage in a vessel lighted from above only.” Before any specimens are introduced into the tank, it should be thoroughly washed out and the glass cleaned on all sides, as this is the only time when it can be done to advantage. We are sure then that no impurity of any kind will thus far hinder the success of the aquarium. The tank then is ready for the rock-work. This rock-work is useful: first, as a shelter for the animals, some

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of them being averse to the light if it is strong; second, as a means of concealing the sediment which, without doing any material injury, so mars the beauty of an aquarium ; third, as a means for anchoring in their proper place the plants we put in; fourth, and lastly, to make the effect of the aquarium more like nature.

It is generally thought that most water-plants, to do well in an aquarium, must have soil to grow in as well as landplants, and that a layer of earth or sand must be spread over the bottom of the tank for the roots; this is found by experience to be a mistake. No earth nor sand is required for the plants which grow best in the aquarium. Either is very apt to spoil the water after remaining in contact with it a short time. Coarse sand is, to be sure, sometimes used when we have animals in the tank whose nature it is to burrow, but even then only in a small quantity placed near a corner of the tank. Some of the small lilies grow better if they have a cubic inch of peat attached to their roots. This small quantity does not injure the water, however long it may remain in it, and is often very useful. In general, however, if the plants are placed right side up, among small stones about the size of a fresh pea, they will grow to any extent, seldom throwing out roots of any kind.

We want, then, a layer of small stones on the bottom, about an inch in thickness; this will be sufficient to bury the ends of the plants in, and to conceal all the sediment which may collect, at the same time giving depth enough for the mussels to burrow in. The stones used with tar for the tops of houses are about the right size for this layer, and on the top of it some larger stones about the size of an almond may be scattered here and there. As to the color of the stones this may add greatly to the effect. If we can have the patience to pick out for ourselves the white and variegated stones from the beaches, we shall be amply repaid by their appearance in water. White stones give a brighter look to the inside of the tank than dark-colored ones, and

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