REARING THE YOUNG FRY. 17! 



taining the equilibrium on which the continuance of 

 organic life depends. 1 * This is a good a priori reason 

 in itself. Besides this, we have the facts that the plants 

 do in practice improve the water, prevent disease, give 

 shelter to the young fry, and furnish more or less nat- 

 ural food for them. They also absorb much of the 

 feculence of the fish for nutriment! 



The larger the young fry grow, the larger the place 

 they can be trusted in ; and it is never desirable to keep 

 them in a smaller place than perfect safety requires ; for 

 the more range they have, other things being equal, the 

 better they will do. Accordingly, as they continue to 

 grow, increase their range, and by the ist of Septem- 

 ber or a little later, when they take their food like old 

 trout, that is, spring for it from their lair and whirl, 

 they can be put into a pond suitable for larger trout, 

 and treated very much as the larger trout are treated. 

 By this time they are much hardier, and less suscep- 

 tible to invisible sources of injury ; they do not stay 

 away alone and get lost, they are better able to take 

 care of themselves ; you can throw them their food 

 very much as you do the larger fish, and they can 



* Self-preserving aquaria have been contrived by lining the 

 sides and bottom of a tank with the most oxygen-giving water 

 plants, so that the fish (not trout] confined in them have lived 

 without a change of water. I am told by a gentleman who has 

 had experience with Barnum's aquaria, that the fish kept in these 

 self-preserving tanks without change of water thrived better 

 than those in the ordinary tanks which had water running through 

 them all the time. 



t The introduction of fresh-water snails accomplishes the same 

 end, but snails are destructive to fish eggs and very young fish. 



