108 CRUSTACEA—OSTRACODA CHAP. 
being pediform and used in walking. The telson in the 
Cytheridae is rudimentary, but is well developed in the Cypridae. 
The heart is altogether absent. 
In many of the fresh-water forms, e.g. common species of 
Candona and Cypris, males are never found, and parthenogenetic 
reproduction by the females appears to proceed uninterruptedly. 
Weismann! kept females of Cypris reptans breeding partheno- 
genetically for eight years. He also remarks on the fact that 
these, and indeed all parthenogenetic female Ostracoda, retain the 
receptaculum seminis, used normally for storing the spermatozoa 
derived from the male, unimpaired. 
Some of the Cytheridae occur in deep water. Thus Cythere 
dictyon was frequently taken by the Challenger in depths of 
over 1000 fathoms, but the majority prefer shallow water. 
The Halocypridae and Cypridinidae comprise marine genera 
Fic. 75.—Asterope oblonga, 9, removed from its carapace, x 25. <A, Alimentary 
canal; A,, Ag, Ist and 2nd antennae ; H, eye ; re gills ; G.O, generative opening ; 
H, heart; M, mandible; 7, 6th appendage ; 7”, last appendage (cleaning foot). 
(After Claus. ) 
of a pelagic habit. The first antennae are chiefly sensory, but 
the second antennae are biramous, and they do not merely move 
up and down, as in the preceding families, but sideways like 
1 «<The Germ Plasm,” Contemp. Science Series, 1893, p. 345. 
