156 DOMESTICATED TROUT. 



And while the patent charcoal troughs can be had, 

 it is not necessary. This irresistible instinct, which 

 drives the alevins past all obstacles to secure a hiding- 

 place, does not seem surprising, when we reflect that 

 it is the only instinct, as well as the only means of 

 self-preservation, which these very clumsy and perfectly 

 helpless creatures have to protect themselves against 

 their myriads of enemies. 



Up to the time when the first half of the yolk-sac 

 period is passed, there is not much danger of loss, 

 except from the little creatures' getting suffocated as 

 just described, because they remain at or near the 

 spot where they were born, and do not roam about 

 much. But after the first half of this stage is over, a 

 new instinct makes its appearance, and it is accom- 

 panied with a new danger, which is both alarming and 

 insidious. This second instinct of the trout is to fol- 

 low a current of water wherever they can find it; 

 usually, but not always, following the current up 

 stream, and diving into any corners, however small, 

 where their delicate perceptions detect the entrance 

 or exit of a current of water. Then woe to the trout 

 breeder if his troughs are not perfectly tight ! for if 

 there is a loose joint in the box, or a nail-hole or aper- 

 ture under or about the screen where water comes in 

 or out, these little creatures will be sure to find it, 

 and one by one will go through it in thousands, even 

 if the crevice is not much larger than would admit a 

 snow-flake. If a beginner were told how small a 

 crevice a six weeks' trout will go through, and has 

 gone through, he would say it was simply incredible. 



