CAKE OF YOUNG IN HATCHING-HOUSE. 107 



too soon, they seem not to have acquired sufficient 

 strength to earn their own living ; if too late, they 

 are stunted in their growth the happy medium, 

 as before mentioned, is about two months. After 

 the first few days of feeding, the gravel should be 

 carefully but thoroughly washed. Turn on as 

 strong a current of water as the fishes can bear, 

 and gently place the hand in the water at the 

 upper part of the topmost compartment of the 

 nursery-trough. The fishes will crowd downward 

 toward the screen. Slowly stir the gravel with the 

 hand, avoiding all sudden motions, until all dirt 

 is carried downward ; then place the hand in the 

 lower part, when the fishes will ascend upon the 

 portion cleaned, and repeat the operation. If the 

 dirt is not carried through the screens, it may be 

 rubbed through ; any large pieces, which will 

 sometimes find their way into the troughs spite of 

 all care, may be removed with the bulb syringe. 

 This tedious but important process should be re- 

 peated at least as often as every third day. If the 

 trays be used, the fish may be drawn out by 

 removing the cork, and replaced after thoroughly 

 washing the tray. 



Sometimes, as has more than once happened to 

 us, in spite of all our care, a sudden epidemic 

 will break out among the fry in the troughs. 

 They may all appear in the evening perfectly 



