AKTIlKol'ODA 



151 



any shieldlike covering, as in Branchipus (Fig. 143), sometimes 

 with the entire body inclosed in a bivalve shell. In some genera 

 the Leaflike, swimming appendages become greatly reduced in 

 number, and this is attended with a great increase in size oi 

 the second pair of antenna-, which become the chief organ 

 of locomotion. This is well seen in the common fresh-water 

 Daphnia (Fig. 144). one of the water fleas; its peculiar appear- 

 ance is increased by the fusion of the two compound eyes into 

 one median compound eye. 



a.nt.1 



1. Branchipus 



an.t.2 

 3. E si- heri a 



FIG. 143. Three Phyllopoda. 3a, shell, external view; 3b, the animal (more enlarj 

 with one valve of shell removed. (7. unpaired process from head; aiit.i, antennule ; ant.2, 

 antenna; ///, heart; m, adductor muscle; md, mandible; ov, ovary; />, copulatory append- 

 ages; sh.gl, shell-gland ; t, testis. (After Gerstaecker, from Parker and Haswell's I 

 book.) 



In the Phyllopoda several pairs of the swimming appendages 

 have gills or respiratory organs attached to them. In the female 

 there is often a brood pouch on the dorsal side of the body, in 

 which the eggs develop. Two kinds of eggs are frequently 

 produced, — the summer eggs, thin-shelled, which develop 

 parthenogenetically, and the winter eggs, which are formed in 

 the autumn, require fertilization and remain quiescent during 



