io8 



CRUSTACEA — OSTRACODA 



Leiiig pedifonn and used in walking. The telsou in the 

 Cytlieridae 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. 

 A\"eismann ^ kept females of Cypris rcptaiis 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 



Fio. 't^.—Astem2)e ohloRga, 9, removed from its carapace, x 25. A, Alimentary 

 canal ; A^, Ao, 1st and 2nd antennae ; Ji, eye ; O, gills ; G.O, generative opening • 

 //, heart; J/, mandible; T. tsth .ippendage ; T, last appendage (cleaning foot)' 

 (After Glaus.) 



of a pelagic habit. The first antennae are chiefly sensory, but 



tlie second antennae are biramous, and tliey do not merely move 



up and down, as in tlie preceding families, but sideways like 



' "The Germ Plasm,"' Contemp. Science Series, 1893, p. M'o. 



