THE OSTRACODA 



secondary shifting of position. A similar organ has been found in 

 one species of Cypridina. 



It is not unlikely that at least one pair of limbs is involved in 

 the composition of the penes of male Ostracods. 



Alimentary System. The oesophagus is narrow and has muscular 

 walls. Its upper or posterior end projects into the capacious mid- 



E. 



FIG. 37. 



A, fourth post-oral appendage of Cypridina mediterranea. B, the same of Macrocyprix 

 succinea. C, fifth post-oral appendage of Cypridina mediterranea. D, the same of Macrocypri* 

 succinea. E, one ramus of the caudal furca of Cypridina squamosa, seen from the side. (After 

 G. W. Miiller.) 



gut, and in the Podocopa is armed internally with chitinous ridges 

 and teeth. In the Bairdiidae this apparatus is most fully developed 

 and forms an efficient "gastric mill," moved by extrinsic and 

 intrinsic muscles, for the trituration of the food. 



The mid-gut in the Podocopa is divided into two parts by a con- 

 striction. Hepatic caeca may be absent as in Cypridina, numerous 

 and small as in Halocypris, or large and reduced to a single pair 

 which may extend into the shell-cavity, as in Cyprididae. 



