458 



CRUSTACEA MALACOSTRACA. 



FIG. 285. A thoracic appen- 

 dage of Nebalia ; I and II 

 segments of the protopo- 

 dite ; en endopodite ; ep 



an exopodite which, in Paranebalia, is narrow and setose, and may 

 show some indication of jointing ; but in Nebalia is expanded 

 into an oval respiratory plate. In the genus, Nebaliopsis, the 

 whole appendage is reduced to a short unjointed lobed plate. 



The anterior region of the abdomen 

 consists of four segments bearing strong 

 swimming feet, having a two-jointed basal 

 portion, and tw r o terminal rami beset with 

 setae. The exopodite is not articulated, 

 but the endopodite has a long distal 

 and a short basal segment, carrying an 

 appendix interna beset with hooks (re- 

 tinaculum) which, with its fellow of the 

 other side, serves to couple the appen- 

 dages together. The posterior region also 

 consists of four segments, of which the 

 two anterior (three in the larva) bear 

 small unbranched vestigial appendages, 

 epipodite; ex' exopodite The anus opens terminally between two 



(from Lang after Clans). J 



setose appendages, which constitute a 

 caudal fork, like that of Branchipus. 



The central nervous system consists of a large brain and a 

 ventral chain of 17 pairs of ganglia, one for each pan- of appen- 

 dages, from the mandibles to the last abdominal (the two posterior 

 abdominal segments have neuromeres in the larva). The ganglia 

 of each pair lie close to one another, and the cephalic and thoracic 

 ganglia are also approximated longitudinally, while the abdominal 

 part of the chain is more elongated, an arrangement similar to 

 that met with in the Schizopods. 



The mouth is guarded by upper and lower lips. Two chitinous 

 masticatory ridges are found on either side of the anterior part 

 of the stomach (malacostracan character), and into the posterior 

 part open on the dorsal side two short blind hepatic tubes 

 which project forward over the brain (cf. Cladocera). On the 

 ventral side three pairs of long hepatic tubes open by two common 

 openings. The latter are similar in structure to the hepatic tubes 

 of Isopods and Amphipods. On the dorsal surface of the intestine 

 in the last abdominal segment, lies a short median tube directed 

 backwards and lined by high cylindrical epithelium. 



The excretory organs are represented by a small antennary 



