62 
pond is emptied of fish in the autumn it is immediately 
laid dry and‘allowed to remain so until just before 
putting fish into it again the next spring or summer. 
The purpose of the soft and rich bottom is to encourage 
the growth of animal life. The laying dry is useful in 
two ways: first, it destroys predatory insects and other 
vermin which, in a pond continually filled with water, 
become so abundant as to prove very destructive to fish- 
food and to the young fish themselves ; second, through 
the drying and freezing it appears to directly encourage 
the development of the eggs of the small crustacea 
which form the most important part of the food of 
young fish. The water-level must be reduced to at 
least a foot below the bottom of the pond, else the 
vermin may not be destroyed. 
Here we have reached what may perhaps be consid- 
ered the most important point in the whole live-food 
business, the encouragement of the food and the 
destruction of the vermin by the simple process of 
laying the pond dry. The life-economy of the small 
crustacea, the entomostraca, is adapted to just these 
conditions, water for a portion of the year, drouth and 
frost for the rest. It can hardly have.escaped ine 
attention of any one interested in these matters what 
multitudes of minute creatures people the pools that 
are filled with water in the spring and dry up in the 
summer and autumn. It is nature’s way, and in devis- 
ing his system Dubisch has simply been following 
nature, 
The most important members of this pool fauna are 
the entomostraca, the daphnids, copepods, ostracods, 
and their relatives. They owe their importance to 
their ability to endure drying and freezing as mentioned 
above and also to the enormous rapidity of their repro- 
duction. A Daphnia, for instance, is endowed with the 
faculty of producing, under proper environment, such as 
obtains in the spring, generation after generation of 
