THE ARTIFICIAL INCUBATION OF OVA. 37 



Place a bit of tile across it to keep it down. In 

 a day or two it will be soaked, and the tile may be 

 removed. Then take the ova in a spoon carefully, 

 and strew it on the bars thickly, so that all are well 

 covered, but not so that one ova rests upon another ; 

 whenever this occurs, with a soft camel-hair brush 

 gently pass it to the nearest vacant space. It is not 

 advantageous for the ova to lay on one another. 

 Indeed, it is decidedly objectionable. The ova being 

 placed, do not disturb them, if you can possibly avoid 

 it, imtn the eye becomes visible in the eggs, when you 

 may do almost what you like with them — pack them 

 up in wet moss, and send them 500 miles off if you 

 please, and even a little squeezing or tossing about 

 (although it is not at all to be recommended) will fail 

 to destroy them, so great is the vitality of the embryo 

 in the egg at this period. But I must confine myself 

 strictly here to apparatus. A tray such as I have 

 described wiU accommodate about 1,100 salmon ova, 

 and about 1,400 trout, and perhaps from 1,800 to 

 2,000 grayling. For greylihg those grilles which 

 have the bars the closest together should be chosen, 

 or the ova is so small and soft that it easily slips 

 through, when it causes much mischief and trouble. 



The volume of stream required is governed a good 

 deal by the quantity of ova you wish to hatch. 



