176 How to obtain it. 



change of water that has been provided, and if the current be all 

 on the surface, it is clear that it would not be advisable to bury 

 the eggs deep in the gravel. The best plan, in such a situation, 

 is to place them on the surface, slightly mixed with the gravel, 

 which prevents them from touching one another. When it is 

 remembered that every egg gives off carbonic acid, the advantage 

 of this will be apparent. 



Some years ago I invented an artificial hatching bed, which 

 has now been thoroughly tested and found to work exceedingly 

 well. It is made of wood, has a lid, and is on the hatching-box 

 principle. In size, it has been found convenient to make these 

 beds twelve feet long, nine inches wide inside, and five or six 

 inches deep. Along the entire length of the box, except for about 

 two inches where the water enters, is fixed a false bottom of 

 perforated zinc. The inflowing water is conducted under this 

 perforated bottom, by means of a water-board placed a couple of 

 inches from the end where the water supply enters. The perforated 

 bottom is placed about an inch above the real bottom, and the 

 water rises up through it. It is coated with asphaltum varnish, and 

 covered with gravel, and upon this gravel the eggs are deposited. 

 At the lower end of the box is the outlet for the escape of 

 the water. This is formed by simply cutting away the upper 

 portion of the box end, say for a couple of inches down. It will 

 be clearly seen from this description that the water on entering 

 the box at one end is conducted direct to the bottom, but passes 

 out at the top, so that it must rise up through the perforated 

 metal and the gravel and eggs upon it. 



Gravel is beneficial in several ways. It tends to prevent over- 

 crowding of the eggs, and it keeps them from coming in contact 

 with the metal. It also provides a more natural bed for the 

 "alevins," and as we are now endeavouring to treat them as nearly 

 according to nature as possible, it is best that it should be so. I 

 have always liked to associate young trout with a clean gravelly 

 bottom as far as practicable, but in a large hatchery, where quan- 

 ./ titles arc dealt with, it is much better not to use it at all. The 

 fish do better and are kept cleaner when they are the sole occu- 

 pants of the rearing box. But in an artificial bed the case is very 

 -different. In the rearing box in the hatchery the fish are obliged 



