CUMACEA. 475 



The second maxillipeds are intermediate in character between 

 the first and the succeeding appendages though they are with- 

 out exopodites. In adult females they bear at their bases short 

 fan-shaped appendages which lie at the anterior limit of the brood 

 chamber, and, apparently, promote the respiration of the young. 



Of the remaining six thoracic limbs two to five of the anterior 

 pairs bear well- developed setose exopodites, springing from the 

 basal joint, by means of which the animals swim. The number 

 of these appendages which are biramous, is greater in the male 

 than in the female. In the abdomen, again, the uropods are 

 alone present in the females, as long and stiff biramous struc- 

 tures, beset with setae like the teeth of a comb, but in the males, 

 short swimming feet are generally found on some of the anterior 

 segments 



In the central nervous system each of the postoral segments (17) 

 is represented by a ganglion. In comparison with other 

 Malacostraca, the Cumacea are very poorly provided with 

 organs of vision. When present at all the eyes form a median 

 group (paired in the larva, and in Nannastacus in the adult) of 

 pigment spots, with several small refracting lenses, situated 

 on the rostrum. They are probably to be regarded as paired 

 eyes, which have become approximated. 



In the alimentary canal a masticatory stomach and generally 

 three pairs of hepatic tubes are present. In Platycuma Holti 

 Caiman has recently described (loc. cit.) a long coiled tract of 

 the alimentary canal (stomodeal ?) a most exceptional condition 

 in Crustacea. 



The heart is oval and lies in the anterior free thoracic segments, 

 and the adjoining part of the cephalothorax. A convoluted 

 shell gland is present in the neighbourhood of the second maxilla. 

 The orifices of the oviducts have not been recognized, but the 

 vasa deferentia open as usual on the last thoracic segment, 

 and the spermatozoa are filiform. A brood pouch is formed 

 in the breeding season by paired over-lapping lobes beneath the 

 fourth, fifth and sixth (the first three free) thoracic segments. 

 The relation of these lobes to the epipodial oostegites of other 

 Malacostraca has not been satisfactorily determined. 



The males of the Cumacea are found at night, swimming in 

 shoals, from which females are absent. The females on the 

 other hand are found more abundantly in sand on the bottom. 



