FISH HATCHING ON A MODEST SCALE 421 



ing over the eggs of the upper tier has been already 

 partially depleted. The whole water-supply system 

 permits of each box being worked as an independent 

 unit. At Luss a cistern and filter within the hatchery 

 were installed and abandoned, as sufficient pressure 

 from these could not be obtained from the delivery 

 pipe to give the flow of water requisite. 



It will be sufficient now to describe one of the hatch- 

 ing boxes arranged for the glass grille system of 

 hatching, and one fitted with the perforated zinc 

 baskets. To take the former first. The glass grille 

 system is the most effective for hatching out ova. It 

 shows a slightly lower percentage of loss than the basket 

 system, but its practical drawback is that it requires more 

 space in proportion to the number of ova hatched. The 

 hatching box is made of \\ in. dressed deal carefully 

 charred inside. It is 6 ft. 9 in. in length, i ft. 7 in. 

 broad, and 7^- in. deep outside measurements. It has 

 wooden ledges on each side of the bottom, and a re- 

 movable wooden runner in the centre placed longi- 

 tudinally. On these rest the four frames carrying the 

 glass grilles. The grille upon which the ova rest is a 

 series of glass tubes, each tube being 6f in. long and 

 \ in. in diameter. The tubes are set in a row close to- 

 gether, but not touching, across each frame, and are kept 

 in position by serrated wood or zinc strips fixed to the 

 inside edges of the frame. The level of the frames in 

 the box is so adjusted that the eggs when placed upon 

 the grille are 3 in. from the bottom of the box, giving 



