754 



THE POPULAR SCIENCE MONTHLY. 



Lower End of Hatching Trough. 



less the eggs flow at a light touch, it is better to return her to the 

 pond, for eggs that have to be forced are not ripe, and if they can 

 be fertilized make weak fish. For the manner of handling the 

 fish, see illustrations from photographs. The so-called "dry- 

 method " is the best. A pan is wet and the water drained from 



it. The eggs of a female 

 are taken by repeated 

 strokes of the forefinger, 

 if the trout is small, or 

 by the hand if large. The 

 eggs will be found to lie 

 the full length of the 

 body cavity, and the 

 strokes begin near the 

 vent and are then worked 

 farther up toward the 

 head. A bending of the 

 back, as shown, often starts the eggs. This operation takes less 

 time than it does to write it, and some water drips from the fish. 

 A male is then stripped over the eggs and water enough to cover 

 them is added, after which they are left to stand until they 

 " free." The eggs are soft as they leave the fish, and for twenty 

 minutes or more they absorb the milt and water, and while doing 

 this they adhere to the pan, but become free when filled. They 

 should not be disturbed until free, when they are washed by 

 changing the water and then are placed on trays in the troughs. 

 If an egg is not impregnated before it fills with water it never 

 can be fertilized, and the advantage of this " dry method " over 

 taking the eggs in a pan of water is that each egg is brought into 

 contact with the milt, which suddenly becomes active when it 

 comes in contact with water. 



This work and all troughs should be in a building and pro- 

 tected from storms and sunshine, but hatching troughs have been 

 successfully worked in the open air. Rats are fond of trout eggs, 

 sediment will smother the embryo within the shell, and direct 

 sunlight will kill it. In a hatching house a distributing trough 

 should run the length of one side. If this is ten inches wide and 

 nine inches deep, with occasional cleats on top to prevent spread- 

 ing, it will be about right. The water may flow in at one end 

 and out at the other, over a dam six or seven inches high. With 

 hatching troughs at right angles to this and supplied by inch-and- 

 a-half cocks or gates the flow will be regular at all times. These 

 cocks should be halfway between the bottom of the distributing 

 trough and the surface of the water, and may have a fine screen 

 above them, or may pour into one below, as seems best, always 

 looking out that the flow is not stopped nor any fine material 



