NATURAL HISTORY. 05 
must be taken that the decomposed vegetation 
does not accumulate, and a little fresh water 
must be added occasionally, preferring rain- 
water. A stem or two of new hay may be 
added from time to time, and the old removed. 
The water fleas (Daphnia pulex, Miill.) and the 
Cyclops quadricornis devour them with avidity, 
and must, therefore, be excluded from the ves-_ 
sel in which they are kept. 
