THE HATCHING APPARATUS. 21 



the trays should be removed, the water syphoned out 

 (unless a tight bung has been fitted in the bottom), all 

 dirt, slime, and grease from the varnish or paint care- 

 fully sponged out, and the apparatus re-filled. The 

 first tray is then floated on the surface, the eggs being 

 carefully distributed on the top of the wires, which are 

 arranged in parallel rows, with cross wires to strengthen 

 them and, if more eggs be at hand, a second tray is 

 very gently laid on top of the first, so as not to disturb 

 the first layer ; this is filled in its turn, and so on, 

 according to the supply. Finally, one empty tray is 

 put on, and the trays are very gently and evenly sunk 

 a little under the surface of the water in the box, and 

 secured by wedges. It has been said that the water 

 must enter at the bottom of the apparatus and flow 

 out at the top, passing through the layers of ova : this 

 may be effected by a side chamber, as in the sketch, 

 or by a pipe carried down outside the apparatus and 

 gaining an entrance by a well-caulked aperture in the 

 bottom. 



For keeping a number of ova in a small space, when 

 fully " eyed," /.<?., when the eyes of the embryo are 

 visible as black dots in the egg, this apparatus, if 

 deftly managed, is very good; but it wants much 

 manual dexterity and experience probably that expe- 

 rience may be bought at too high a price by the 

 amateur. In some cases there is a pipe fitted in the 

 bottom with a portion of indiarubber pipe attached, 

 and stopped with a wooden plug ; so that if any of 

 the young fishes fail to swim up -with the current, 

 which must not be too strong until all are on the eve 

 of hatching, they may be drawn off by the hose into 

 a vessel placed beneath to receive them. 



