362 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Each jar will incubate 200,000 eggs of the whitefish. Tauks of uniform 

 size are placed one above the other in three tiers, and the water enters 

 the upper tank and feeds a row of jars on either side, whence it is dis- 

 charged into the middle tank to supply another double row of jars, 

 thence passing into the lower or waste tank. The jars rest in pairs on 

 narrow shelves placed crosswise of the tanks. 



During the season of 1SS1-'S2 an improved whitefish incubator was 

 devised by employes of the hatchery. The egg-chamber is substan- 

 tially the same as that of the automatic jar; but the separation of the 

 dead and living ova is more perfectly accomplished by improved dis- 

 tributive arrangements, which give to the currents of water absolute 

 evenness and uniformity. A cone-shaped device is fitted to the bottom 

 of the egg-chamber, and resting on this is the tube through which the 

 water is introduced. The bottom of the tube assumes a conical form to 

 correspond with the cone over which it is placed, being slightly raised 

 or separated therefrom by narrow strips of tin soldered to the cone 

 midway between its base and apex, to permit the water to escape. The 

 column of water in its descent through the tube is pierced by the apex 

 of the cone and radiated to the base of the tube, where it escapes into 

 the egg-chamber. Side currents are thus formed which impart to the 

 eggs the best possible motion 5 carrying them upward through the egg- 

 chamber to descend again upon the base of the tube, which diverts 

 them to its edge to be carried up again, as before, by the inflowing 

 current. Fifty of these incubators are now employed at the North- 

 ville hatchery, and over two hundred at the Lake Huron hatchery, 

 recently established at Alpena, Mich., by the United States Fish Com- 

 mission. 



As an experiment, Mr. S. Bower, of the Northville hatchery, con- 

 structed an incubator admitting of a larger scale of operations, at a 

 greatly reduced cost for apparatus. It is made of wood and galvanized 

 iron, in the form of a rectangular box, and is divided into upper and 

 lower chambers; it is 11 inches wide by 13 inches deep and 30 inches 

 long, although its length is not* material, and may be extended indefi- 

 nitely, increasing its capacity to correspond, without impairing or 

 changing its operation. The movement of the eggs is obtained by 

 introducing water into the lower chamber, whence it is admitted to the 

 upper chamber through a sixteenth-inch crevice running lengthwise 

 of the box. From each side the partition which divides the box into 

 two chambers slants downward to the point where the water enters 

 the egg-chamber. By this means the eggs carried to the surface by the 

 inflowing current are constantly returned to the starting point, and 

 thus a perpetual circuit is produced. The principle of operation thus 

 reverses the motion employed in the jars, as the eggs ascend from the 

 center and descend at the sides, instead of rising at the sides and 

 returning through the center. Overflows are provided at intervals 

 around the top of the box. The separation of the dead and living ova 



