
206 A FISH FARM. 
The hatching troughs (Fig. 40, e) are placed at right an- 
gles to the others, and are sixteen feet long, fifteen inches 
wide, and eight inches deep, and are six in number with cov- 
ers upon hinges, the top of them being about fifteen inches 
from the floor. They are lined with slate, one-half of an 
inch thick, upon the sides and bottom, with transverse sub- 
divisions; every two feet made of the same material and two 
inches in height. A fungus growth, very detrimental to the 
ova, is unavoidable when wood only is used. The bottom 
of the troughs is covered with about one inch of moder- 
ately fine gravel, and over it flows a constant stream of 
screened spring water about an inch deep, the lower end 
of the trough being depressed two inches. On this gravel 
the impregnated ova are placed in a single layer. In about 
three weeks the eyes can be seen in the impregnated eggs, 
appearing simply as two black specks; the blood-vessels of 
the future fish may also be seen, and from this time its de- 
velopment may be traced daily in the shell. With the tem- 
perature of the water at 489, we may look for the hatching 
of the ova from the forty-fifth to the fiftieth day. A trout 
just hatehed is about three-eighths of an inch in length, and 
has attached to it an umbilical sac of several times its own 
bulk, which sustains the young fish for about forty days, 
when it is absorbed. The young fish may now be let out 
into the waters it is desired to stock. They will thrive if 
placed in a brook even at this early age, such waters sup- 
plying an abundance of minute particles of food. If reared 
in confinement, however, they must be fed with raw liver 
chopped to the consistency of blood and mixed with water, 
with the yolk of eggs grated very fine and treated in the 
same way, or thin sour curds. The latter food is perhaps 
the best as it sinks more slowly, and trout seize their food 
tn transitu, paying little attention to it after it reaches the 
. We have sought only to give guch a general description 
of a fish breeding establishment, and of the habits and treat- 


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