262 AQUATIC MICROSCOPY FOR BEGINNERS. 



carnivorous crustaceans are so constituted that their 

 diet is nearly confined to such floating particles of 

 matter as are present in the water in a state of more or 

 less fine comminution; for, nearly without prehensile 

 organs, these animals, by means of a valvular or, at 

 most, ladle-like labrum, dip from the current of water 

 kept flowing by the constant rhotion of the branchial 

 feet, such fragments as the snail .and scavenger-fish 

 have disdained; bits of decaying Algae, or the broken 

 fragments of a disintegrated mosquito, all alike accept- 

 able and unhesitatingly assimilated. The amount of 

 such material that they will dispose of in a short period 

 of time is truly astonishing." 



When the shallow ponds are dried by the summer 

 heat, the Entomostracans bury themselves in the mud, 

 and there remain quiescent, but alive, so long as any 

 moisture is present. When the mud is corhpletely 

 dried they die, but the eggs have the ability to endure 

 heat and dryness without injury, and to develop and 

 mature as the pools aga'n become filled by the rain, or 

 by the melting snow of early spring. 



The Pbyllopoda may likewise often be recognized 

 without a microscopical examination, in this case by 

 their large size and' their almost universal habit of 

 swimming on the back. Branchipus, sometimes 

 called the fairy shrimp, and Arte'mia, or the brine 

 shrimp, are nearly an inch in length. 



As in the Entomostraca, the bodies of the.Phyllo^ 

 poda may be incased in a bivalve shell or not. The 

 broad, flattened feet are numerous, but .the branchial 

 or breathing-plates already referred to may be small 

 and inconspicuous, and" therefore difficult to be ob- 

 served by the beginner. They are especially well- 



