CARE OF ALEVINS. 155 



or holes in the hatching troughs where they can so 

 entrap themselves, for they will certainly do it. 

 The instinct is so ceaseless that it seems to drive 

 them on farther and farther, without any thought 

 of turning back. I have seen a thousand at a time 

 white and dead with suffocation under a pane of 

 glass in the hatching trough, whither this instinct had 

 pushed them on and on to this fatal termination. 

 Here arises a serious objection to the use of hatching 

 troughs with uncemented glass linings. The glass 

 prevents the growth of fungus to some extent, it is true, 

 but there is always danger of the alevins getting un- 

 der the glass and becoming suffocated, as in the case 

 just mentioned ; and so invincible is their instinct to 

 do this, that they will constantly try to return under 

 the glass, even when they are just taken out white and 

 almost dead with suffocation. If, however, the reader 

 should happen to use loose glass linings, or any lining 

 or hatching bed of any kind which the young crea- 

 tures can get behind or under, he is here cautioned to 

 examine every day, and see if any are hidden in dan- 

 gerous places, and, if so, to liberate them at once It 

 is true that after the eggs are all hatched the linings 

 can be taken out, but as this is so difficult to do, with- 

 out burying some of the fish under the gravel, and as 

 it also releases the fungus behind the glass upon the 

 young trout, the remedy is almost as bad as the dis- 

 ease ; and besides this, it is no remedy at all for the 

 earlier-hatched alevins, which must necessarily be ex- 

 posed to the danger some time before the glass is 

 ready to be taken out. 



