Page:Popular Science Monthly Volume 7.djvu/519

Rh Bad Health of American Women. By James E. Reeves, M.D. Wheeling, Va. Pp. 43. Price, 50 cents.

Animal Volition a Creator. By C. G. Forshey. (New Orleans Academy of Sciences.)

Papers read before the Pi Eta Scientific Society of Troy Polytechnic Institute. Pp. '74.

Oldbury. By Annie Keary. Philadelphia: Porter & Coates. Pp. 420. Price, 81.25.

The Complete Arithmetic. Also, First Book in Arithmetic (Fish). Ivison, Blakeman, Taylor & Co.

Determination of Minerals by Blowpipe (Danby). London: Field & Tuer.

St. Louis Public Schools.

Bulletin of the Bussey Institution.

Morgan Expedition, 1870-'71

Archæological Researches in Kentucky and Indiana (Putnam).

Hygiene of the United States Army.



Fish-Culture.—The results so far attained in this country in the artificial culture of fish are eminently satisfactory, and the efforts made by the various fisheries commissions to increase the supply of food for the people are worthy of all commendation. Naturally, there exists a lively public curiosity to know the processes of fish-culture, and information with regard to its history, its principles, and its methods, is heartily welcomed. In response to this general demand, Mr. Robert B. Roosevelt, Fish Commissioner of the State of New York, has given a public lecture on pisciculture, in which he very fully considers the subject in all its aspects. The lecture is very long, and we must be content with indicating only a few of its points. There are, he said, two divisions of fish in our country which are subjects of fish-culture, viz., the Salmonidæ, or salmon-tribe, and the Alosidæ, or shad-tribe. Under the former head are included the salmon, the trout, the salmon-trout (or lake-trout), the whitefish, and the California salmon. The Alosidæ are represented in pisciculture only by the shad, as yet.

The first point in fish-culture is to obtain the spawning-fish in proper condition. In the Salmonidæ, the eggs, when in a perfectly ripe condition, lie free in the abdomen, and may be extruded by gentle pressure. They are caught as they fall in a basin, and are vitalized by coming in contact with the milt from the males. Formerly, the practice obtained of having this basin full of water, it being supposed that this arrangement more nearly reproduced the natural conditions; but subsequent discoveries led to a change of this method. The eggs are fertilized by the spermatozoa of the milt entering through the micropyle, and taking up board and lodging within. It was ascertained, however, in practice, that these spermatozoa are not fond of water, and, although very active when first emitted, soon drowned. They retain their vitality much longer when dropped among the eggs in a comparatively dry state, and this is the method universally pursued at present.

As soon as the operation is completed, the eggs are placed in hatching-troughs. These are made of various materials, but are simply long, narrow boxes, say twelve feet long by eighteen inches wide, and subdivided into compartments, to keep the eggs from crowding on one another. Cold spring-water, which has been carefully filtered by passing through several flannel screens, comes in at the head of these troughs, passes over the eggs, in one compartment after another, and escapes at the lower end. By this means the greatest dangers to the life of the embryo are avoided. Sediment and confervæ cannot pass the screens, insects are kept out altogether, and ducks and eels are disappointed of their prey. The eggs require about two months to hatch, with the water at the temperature of 45°. They demand constant care and attention, for, if one egg dies or becomes diseased, it contaminates its neighbors. The advance of the process is, however, soon visible in the egg, either to the human eye or under the microscope. At last the pisciculturist will have evidence of his labors being successful. Some morning, on going to his troughs, he 