PROPAGATION OF FISH. 255 



determined by the velocity of the current. The water 

 striking against the screen enters the minute interstices, 

 and lifting the eggs, keeps them in gentle motion like 

 the bubbles of air in a pot of moderately boiling water. 

 All that is necessary is to attach these boxes one behind 

 the other in a long row, anchor them in the river, and 

 fill them with impregnated spawn, and the work is done. 

 The continuous motion of the water passing around 

 each egg and holding it suspended, aerates it perfectly 

 and makes its hatching a certainty. Hardly one per cent, 

 of healthy eggs fail to hatch, and while the process is go- 

 ing on hardly any care or attention is required. Fish 

 and eels cannot enter the boxes to prey, nor can the 

 eggs be driven out by the water, and lost. 



In the artificial manipulation of shad the parents are 

 taken in seines from their spawning beds. The haul is 

 made at night, at which time only can ripe fish be found 

 in any considerable number. The captured fish are 

 thrown indiscriminately into a boat and are stripped at 

 once as they die quickly. They are afterwards sold in 

 the markets. The eggs, which are caught in a pan with 

 a little water in it, after being allowed to stand for a few 

 minutes until impregnation is complete, which is sig- 

 nified by their swelling in size and reducing the tempera- 

 ture of the water some ten degrees, are poured into the 

 hatching boxes and left to themselves. Nothing more is 

 required. In twenty-four hours the black eyes of the 

 young fry will be visible through the shell, and in from 

 three to ten days they will be hatched. 



Black bass is one of the most prolific varieties of our 

 fresh-water fish. Their natural increase is so great and 

 their growth so rapid, that it has never been an object to 



