EXCRETORY AND NERVOUS SYSTEMS 147 



D. The Excretory System. 



1. The kidneys, or 'green glands,' are a pair of rounded 



and somewhat flattened bodies, of a light green 

 colour, lying in the ventral part of the head, in front 

 of the mouth. 



2. The ureters are a pair of wide thin-walled sacs, lying 



one on the dorsal surface of each kidney. Each 

 ureter communicates directly with the cavity of its 

 kidney, and opens to the exterior by an aperture 

 already seen on the hinder surface of a tubercle on 

 the basal joint of the antenna. 



•Inflate the ureter by blowing air in at its external aper- 

 ture. 



E. The Endophragmal Skeleton. (Fig. 35, p. 140.) 



In the thorax a series of calcified plates project inwards 

 from the cuticle of the ventral surface, forming an internal 

 skeleton, which gives origin to the muscles of the legs and to/ 

 the powerful flexor muscles of the abdomen. 



P. The Nervous System. 



1. The central nervous system consists of a series of 

 ganglia arranged in pairs, and united by paired 

 bundles of nerve-fibres, or connectives, to form a 

 chain, which runs along the whole length of the 

 body close to the mid-ventral line. The two ganglia 

 of each pair are usually fused indistinguishably. 



a. The pre-oesophageal ganglionic mass, or ' brain,' is 



a white mass of considerable size, situated just 

 behind and slightly above the bases of the anten- 

 nules. It gives off nerves supplying the eyes, 

 the antennules, and the antenna. 



b. The para-oesophageal connectives are a pair of long 



nerve-cords, one on each side of the oesophagus, 

 connecting the ' brain ' with the hinder part of 

 the nervous system. They are connected with 

 each other by a transverse commissure, imme- 

 diately behind the oesophagus. 



L 2 



