426 



CRUSTACEA. 



as the long cylindrical appendage of Cypridina, winch arises In place 

 of the seventh pair of legs, almost on the back of this animal. 



The nervous system consists of a bilobed cerebral ganglion and 

 a ventral chain with closely approximated pairs of ganglia, which 

 may unite to form a single ganglionic mass. 



Sense organs. In addition to the already mentioned olfactory hairs 

 there is a median eye (Gypris, Cy there), composed of two (often 

 separated) halves ; or there are, in addition to a small unpaired eye, 

 two larger compound and movable lateral eyes (Cypridina). In 

 Halocypris and Cypridina there is a frontal appendage, which 

 probably functions as a sense organ. 



Alimentary canal. The mouth, which is frequently (Cypris) 

 armed with toothed lateral bands, leads through a narrow resophagus 

 into a dilated crop-like portion of the alimentary canal. This is 

 followed by a broad and long stomach, provided with two long 



lateral hepatic tubes, which 

 project into the lamellae of 

 the shell. The anus opens at 

 the base of the abdomen (fig. 

 337). Of special glands a 

 club-shaped, dilated glandular 

 tube (poison-glands ?) found 

 in Cy there must be mentioned, 

 T- the duct of which opens to 



FIG. 33/ . Alimentary canal and generative 



organs of a female Cypris (after W. Zenker). the exterior through a spinous 

 Oc, ossophagus : PF, crop; T* stomach ; D, i ,1 , 



intestine; x] liver ; Or, ovary ; ,W/, adductor appendage <>f the posterior 



muscle; R receptaculum ; Vu, vulva; Fa, antennse. 

 caudal fork. . , , . _, 



A neart is present in Cypri- 

 dina and Halocypris on the dorsal surface, where the shell is con- 

 nected to the animal. The function of respiration is performed 

 by the whole surface of the body, over which an uninterrupted 

 current of water is maintained by the swinging movements of 

 the leaf -shaped setose branchial appendages. In many Cypridinidw 

 (Asterojye) there is a double row of branchial tubes on the back, 

 near the last pair of appendages. 



Generative organs. The sexes are always separate and are dis- 

 tinguished by well marked differences in their entire structure. The 

 males, in addition to the greater development of the organs of sense, 

 possess apparatuses on different appendages in Cypridina on the 

 second antennae, in Cypris on the maxilliped for holding tho 

 females ; or a pair of legs may be completely modified for this pur- 





