FOOD OF FISH AND ITS PRODUCTION. 95 



Here is a point well worthy the consideration of 

 those who wish to take up the science of pisci- 

 culture. What particular species of food can it be 

 which not only makes up for the total absence of 

 the may-fly and mianow, but so feeds the fish in this 

 admirable little stream, that there is no river, large 

 or small, which I have ever seen in all England, 

 can for its size equal it in production? "What, then, 

 can be the particvdar food that fattens them so 

 rapidly ? 



My own impression is, that the fresh-water 

 Pulex, or Screw, which I have previously referred 

 to once or twice, has not a little to do with it, 

 for these insects abound in this stream even to 

 profusion — to a greater extent, indeed, than I have 

 ever found them in any other brook. The trout 

 feed upon them voraciously; and it is a very common 

 thing to find in the trout a mass of these insects, 

 half digested, and as large as a filbert. I have seen 

 the trout picking them off the walls, which pen the 

 stream in some places, as rapidly as a child would 

 pick blackberries from a hedge; and I am induced 

 to think that this insect has, as I have said, much 

 to do with the fineness of the fish; and the more 

 so, because, when I have found it to exist in 

 any quantity, I have invariably observed that 



