152 DOMESTICATED TROUT. 



haps, will hatch in one day, during a warm rain, than 

 in the three subsequent days. 



The newly hatched fish are about half an inch in 

 length. The yolk of the egg is still attached to them, 

 from which they are nourished by absorption till it is 

 all gone and they begin to feed. The period of ale- 

 vin life is about two thirds or three fourths the length 

 of the period of incubation. 



Its duration, like that of the egg period, depends on 

 the temperature of the water, and it often happens, in 

 water of a falling temperature, that the yolk-sac period 

 lasts longer than it took the eggs to hatch. 



On the contrary, with eggs hatched late in the 

 spring, as in the natural brooks, with a rising tempera- 

 ture, the yolk sac remains on a very short period com- 

 pared with the hatching of the eggs, — probably in 

 some instances not one quarter of the time. 



During the period while the young fish are breaking 

 the shell, the bottom of the troughs becomes quite un- 

 clean from the collecting of cast-off shells and other 

 causes, and it is a good plan to use the watering-pot 

 freely at this time ; and as soon as it can be done 

 without injury to the young fish, the bed of the troughs 

 should be covered over with a layer of fresh clean 

 gravel. 



The alevins lie quite still the greater part of the time 

 at first, sometimes on their sides, sometimes flat on the 

 sac. Occasionally they vary the monotony of this quiet 

 life by aimless sallies of a few inches through the water, 

 apparently in great excitement, but with no particular 

 goal in view. The exertion will soon bring them to 



