CuapterR XXI. 
THE CRAY OR CRAW-FISH 
(Astacus fluviatilis) 
Is also known as the fresh-water lobster, and should be killed 
whenever and wherever met, as it is very destructive to the eggs of 
fishes. 
It will also occasionally catch a young fish, and often injure 
others by snapping at them, tearing away parts of the fins and flesh, 
thus rendering a beautiful and valuable fish wholly valueless as 
merchandise. 
The main damage done by the craw-fish, however, is the under- 
mining of the dams, which is not only annoying and costs much time 
and labor for repairs, but makes it possible for the fish in the several 
ponds to get mixed by passing from one to the other. 
THE WATER-FROGS 
(Rane var.) 
As the heading indicates, there is a recognized distinction between 
frogs, there being water-frogs, tree and grass frogs, the latter in no 
ways molesting the fish in the ponds, in reality on the contrary, 
making themselves very useful to the culturist by destroying harm- 
ful insects. The common frog is the one we have to guard against, 
both itself and all its varieties, whose destructive habits far outweigh 
the little benefit derived from them. Just as soon as they have 
completed their gradual metamorphosis, and become perfect frogs, 
they prey upon anything that has life, including young ducks, turtles, 
snakes and cray-fish, as well as fish. Besides this, the adult deposits 
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