156 THE CEAYFISH. 



nules. It gives off nerves supplying the eyes, 

 the antennules, and the antennae. 



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

 nerve-cords, 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. 



c. The post-oesophageal ganglionic mass is an ovoid 



mass, lying a short way behind the mouth. 

 From it arise the nerves supplying the mandibles, 

 both pairs of maxillae, and the first and second 

 maxillipedes. 



d. The thoracic nerve-chain consists of six ganglionic 



masses, united by paired connectives, and supply- 

 ing the appendages from the third maxUlipedes 

 to the last thoracic legs. The first one is situated 

 immediately behind the post-oesophageal gan- 

 glionic mass, with which it is closely connected. 

 The connectives between the fourth and fifth 

 ganglionic masses diverge slightly, and the sternal 

 artery (p. 160) passes between them. 



The thoracic nerve-chain lies beneath the eiidophragmal 

 skeleton, which must be removed to expose it. 



e. The abdominal nerve-chain consists of six ganglionic 



masses, joined by connectives, and supplying the 

 abdominal segments and their appendages. The 

 hindmost ganglionic mass is larger than the 

 others, and supplies both the nineteenth segment 

 and the telson. 



2. The visceral nervous system. 



This can only be dissected in a specimen in which the 

 alimentary canal has been left undisturbed. 



a. The anterior visceral nerve is a median nerve 

 formed, just in front of the oesophagus, by the 



