BNT0M08TRA CANS. 



87 



number of legs having meanwhile increased, are enclosed 

 by two sets of valves, so that the animal appears as if bi- 

 valved (Fig. 102), and at last the barnacle-shape is at- 

 tained. 



Order 2. Entomostraca (Water-fleas).— The type of this 

 group IS Chjdops (Fig. 103), in which the body is pear- 



Fig. 103.— Ci/c?ops. e, eye; ft, heart; 

 eg, eggs ; /, feet. Highly mag- 

 nified. 



Fio. 104.— Lemasa of 

 the cod. /i, head;ou, 

 ovary. Nat. size. 



Fig. 105. —Fish 

 louse of the 

 menhaden. 



shaped, with a single bright eye in the middle of the head; 

 it has two pairs of antenna, used for swimming as well as 

 feelers; biting mouth-parts, and short legs. The females 

 swim about with two egg-masses attached to the base of 

 the abdomen. The young is a Nauplias, much like that 

 represented in Fig. 112), ih? mouth-organs, the legs and 



