roS 



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 l kept females of Cypris rcptans breeding partheno- 

 genetically for eight years. He also remarks on the fact that 

 these, and indeed all parthenogenetic female Ostracoda, retain the 

 receptaculum semiuis, used normally for storing the spermatozoa 

 derived from the male, unimpaired. 



Some of the Cytheridae occur in deep water. Thus Cy there 

 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 



-T' 



Kin. 7">. Asterope <i/./nn</<i, 9, ivmovrd from its carapace, x 25. A, Alimentary 

 canal ; .1,, Jo, 1st and 2ml antennae ; I-:, i-y.- ; t; : gills ; <v.o, generative opening ; 

 //, heart; M, mandihlc : T, t>th appendage; 7", last appendage (cleaning foot). 



(After Clans.) 



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 (ierm Plasm," (.'mif,-,,,/,. Science Xcrics, 1893, p. :iir>. 



