422 THE KEEPER'S BOOK 



that depth of water beneath them, while the water-level 

 is maintained at half an inch over them. As it is im- 

 portant to strain the water of all sediment, the nose-cock 

 at the upper end of the box discharges first into a per- 

 forated zinc strainer, which, with a further inch or two of 

 space before the trays are reached, distributes the inrush 

 of water to the box in a uniform gentle flow. At the 

 lower end of the box a removable perforated zinc screen 

 prevents any egg lapping over into the lower box, and, 

 later, prevents the escape of the alevins and fry when 

 the eggs hatch out. 



Between the system of glass grilles and the per- 

 forated zinc baskets the only difference in principle is 

 that the eggs on the grilles are laid in uniform rows, while 

 in the baskets they are deposited in mass, perhaps two, 

 perhaps three, layers deep. At Luss two layers deep 

 has been found to produce results equal to the grilles, 

 while hatching double the quantity of ova, that is, the 

 proportion of loss is no greater, the total loss being in 

 both cases from two to three per cent. only. The baskets 

 are carefully made of finely and closely perforated zinc 

 sheets and are 8 in. square and 3 in. deep. Two rows 

 of eight baskets occupy the space in the hatching 

 box, a number sufficient for convenience of working. 

 The whole sixteen baskets rest upon the longitudinal 

 side ledges and central runner already described, 

 at such a level that at least three-quarters of an inch 

 of water will flow freely over three layers of eggs. 

 When it is added that, as in the upper boxes, a strainer 



