962 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



The water passes through from below upward, and the weight of the fishes 

 constantly tends to keep them away from it and assists them to clear them- 

 selves if once drawn against it. If there is a very strong current this is the 

 only safe screen. It is nothing unusual for young fish to get against an 

 upright screen and, the current being pretty strong, be unable to get away 

 from it, and if the screen be too coarse their sacks are often drawn through, 

 to their almost certain destruction. The safety screen should be sunk an 

 inch or two below the top of the dam. 



12.— TREATMENT OF THE EGGS. 



If the foregoing instructions for the erection and fitting of the hatching- 

 house have been judiciously followed, the task of caring for the eggs and 

 young fry will not be a very difficult one, but will nevertheless demand 

 constant alertness. 



When eggs are received from other stations, it is important to lose no 

 time in opening the package and ascertaining their condition. If the eggs 

 are packed in moss, plunge the bulb of a thermometer into the moss under 

 several layers of eggs, taking care to admit the least possible amount of 

 outside air ; cover it up and wait fifteen or twenty minutes, when it can be 

 examined and the general temperature of the package ascertained pretty 

 nearly. If it is within six degrees of the temperature of the hatching- 

 water the eggs may be immediately placed on the hatching-trays. If, 

 however, the temperature of the moss is six degrees higher or lower than 

 the hatching-water, it is better to drench the boxes with water of inter- 

 mediate temperature, several times if the difference be very great, to bring 

 the eggs gradually to the temperature of the water. After this the sooner 

 the eggs are placed on the trays the better. If it is impossible to avoid wait- 

 ing, (over night, for instance,) let the packages stand in a room of safe and 

 uniform temperature, (hatchmg-house or cellar,) but never let packages of 

 eggs stand in water. If the eggs are packed in the mode now commonly 

 adopted, between folds of mosquito net and layers of moss, first remove the 

 upper moss carefully and then lift them out, a whole layer at a time, on the 

 cloth on which they lie, and turn them into a pan of water, from which 

 bits of moss, &c., can be picked out or rinsed oif. An even distribution 

 of them on the trays will be facilitated by measuring them out in a meas- 

 ure Tiolding just enough to cover a tray. 



Once deposited on the trays the necessary work is comprised in a simple 

 routine. The dead eggs and fish turn white and must be removed before 

 they taint the water. It is better, but not essential, to have a table or 

 sink to do this work on, and a broad shallow square or oblong pan to set 

 the tray of eggs in while picking, that they may not remain long out of 

 water. This pan will also be convenient to rinse the eggs in, should they 

 become very dirty. At any time after the eyes of the embryo become 



