TEOUT 



the first year at any rate, and a good fly may 

 thus be introduced into a water where it was 

 before unknown. 



I have already spoken of the fresh-water 

 shrimp and the water-flea (Daphnia pulex). 

 These valuable articles of diet should be intro- 

 duced whenever it is possible. Daphnia must be 

 reared in a stagnant pond, the fresh- water shrimp 

 (Gammarus pulex) in running water, with plenty 

 of weeds. 



Other useful creatures besides those snails and 

 mussels which I described in a previous chapter, 

 are the water-louse (Asellus aquaticus), Cypridce, 

 and Cyclops quadricornis. Asellus is very similar 

 in size and shape to the common garden-louse, 

 which is found in decaying wood. It will live 

 either in stagnant or running water. Cypridce 

 are very much smaller, being generally only as 

 large as a large pin's head. They have a bivalve 

 shell which makes them look something like a 

 small mussel. They are, however, very active, 

 swimming by means of two pairs of legs. They 

 also possess two pairs of antennae and one eye. 

 (The species belonging to the genus Candona of 

 the family Cypridce, do not swim.) Cyclops is 

 another very small crustacean, shaped like a 



65 p 



