Artificial propagation of the shad and pike perch . o control the water levelin the collector-tank. Long-handled nets of ^-inch mesh are requiredto remove egg lumps or other matter from the jars. THE AUTOMATIC HATCHING-JAR. The United States Fish Commission, in the development of itswork, had presented to it the necessity of dealing with the eggs of the whitefish and the shad upon ascale unprecedented in the his-tory of fish-culture. Millionswere to be handled instead ofthousands, and the removal ofdead eggs by hand picking wasno longer to be successive experimentsthe McDonald
Artificial propagation of the shad and pike perch . o control the water levelin the collector-tank. Long-handled nets of ^-inch mesh are requiredto remove egg lumps or other matter from the jars. THE AUTOMATIC HATCHING-JAR. The United States Fish Commission, in the development of itswork, had presented to it the necessity of dealing with the eggs of the whitefish and the shad upon ascale unprecedented in the his-tory of fish-culture. Millionswere to be handled instead ofthousands, and the removal ofdead eggs by hand picking wasno longer to be successive experimentsthe McDonald automatic hatch-ing-jar was devised, and it isnow generally employed. The most meritorious featureof this apparatus is that itprevents the development ofthe saprolegnious fungus, whichcaused so great a mortality insome other forms of hatchingcontrivances in which all the ovawere not in continual very gradual, gentle, andcontinual rolling movement ofthe ova upon each other in thejar apparently prevents thespores of the fungus from ad-. Automatic shad-hatching jar. hering. The cleanliness of the apparatus is also advantageous, and asthe material of which it is made is glass, the progress of developmentcan be watched satisfactorily from the outside of the jar with a handglass or pocket lens of moderate power. The jar is a cylindrical glass vessel, of about 7 quarts capacity,with hemispherical bottom, supported upon three glass legs. The topis made with threads to receive a screw cap. It is closed by a metallicdisk perforated with two holes five eighths inch in diameter—one inthe center admits the glass tube that introduces the water into thejar, the other, equally distant from the central hole and the edge of MANUAL OF FISH-CULTURE. 139 the metal plate, admits the glass tube which carries off the wastewater. The central tube is connected by half-iuch rubber tubing withthe pet-cock, which regulates the supply of water. A groove in theinner surface of the metallic pl
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