70 AMERICAN FISH CULTURE. 



above the wire screen at the end of each trough, as the fry 

 will leap over the top if it is only an inch or so above the 

 surface, and thus make their escape. When, from their 

 numbers and size, the hatching-troughs become too small to 

 accommodate them all comfortably, they may be lifted out 

 with the small net and placed below. It is well, also, to 

 keep the bed of gravel at the top of each trough an inch or 

 two above the surface, as they have a disposition to wriggle 

 over, if it is even the eighth of an inch in depth, and run 

 up the little jet from the supply-trough, then into the 

 filterer, and even into the supply-pipe. Concerning their 

 disposition to escape from the nursery, Mr. Ainsworth in- 

 formed me he once missed many of his fry, and found them 

 in a pond where he kept his large fish. After many days' 

 search for the place of exit, he found that one of the plauks 

 had a hole the size of a quill in it, eaten by a wood- worm 

 before it was placed there ; through this, an earth-worm 

 which had found it, made its way, and then through a 

 bank of clay five or six feet to the large pond ; the fry had 

 escaped along this narrow channel. I had a like experi- 

 ence at the establishment which I started in Warren 

 county, New Jersey ; many thousand of the fry escaping 

 through a crack in the mason-work, not more than wide 

 enough to thrust the blade of a stout breakfast-knife in. 

 These little matters of experience I jot down to show the 

 necessity of having the sides and ends of the nursery of 

 sound plank, and of providing against every chance of 

 escape. 



A month or six weeks after the fry commence feeding, 



