294 



ARTICULATA. CRUSTACEA. 



the Order BRANCHIOPODA,* or those in which the 

 feet appear to serve the purpose of lungs or gills. 

 The body is contained between two transparent oval 

 plates, open on the under edge. Through this pellu- 

 cid envelope the legs may be seen in constant motion, 

 and, from the extreme delicacy of their covering, 

 they present to the surrounding element a surface 

 of sufficient extent for the purpose of exposing the 

 blood to its action ; while at the same time, by a 

 beautiful provision, the more active and vigorous 



WATERFLEAS : 1. Cyclopa Communis, 2. Cypris Unifasciata, 

 3. Dap/mia Pulex. 



their motions are, the more effectually will a current 

 of fresh water pass along the breathing surface, to 

 support the muscular energy. During the heat 

 of the day, these little Waterfleas descend to a depth 



* By;s, branched, the gills, and -rovs, pous, a foot. 



