BUSYCON. 139 



that covers the ganglia and notice on the ventral side of the 

 esophagus : 



1. The small but conspicuous buccal, ganglia. These are 

 united with each other and with the cerebral ganglia and send 

 nerves to the mouth apparatus. 



2. The large 'pedal ganglia, fused together but distinctly 

 paired, lying posterior to the buccal ganglia and sending nerves 

 to the two sides of the foot. Each is united by connectives with 

 the corresponding cerebral and pleural ganglia. 



From the dorsal side a number of ganglia may be seen, more 

 of which lie to the right than to the left of the median line. 



1. On the left side there are two ganglia that are in rather 

 close union with each other. The most anterior, the left cerebral, 

 is the larger of the two. The left pleural joins it posteriorly and 

 ventrally and extends nearly to the ventral side of the esophagus. 



2. On the right side four ganglia may be distinguished. The 

 right cerebral and right pleural are fused to form one mass, but 

 there is a marked constriction between them. Posteriorly and 

 dorsally the right pleural is connected by a connective with the 

 right parietal, which lies very close to it. The remaining gan- 

 glion, the left parietal, which is almost in contact with the right 

 pleural and right pedal ganglia, lies ventrally and to the right of 

 the right parietal ganglion. It is connected with the left pleural 

 ganglion by a connective that runs behind the pedal ganglia. 

 There seems also to be a connection with the right pleural gan- 

 glion, but this must be considered a secondary connection. Do 

 you understand how this ganglion comes to have this position? 



3. Another ganglionic mass, the visceral ganglion, possi- 

 bly formed by the fusion of two ganglia, lies just below the exter- 

 nal opening of the kidney, where it can be seen as a brown mass 

 through the body-wall. It lies on the elongated commissure 

 that connects the two parietal ganglia. The commissure may be 

 followed by dissection. 



The cerebral ganglia are the most centralized. Besides 

 being connected with each other by a commissure dorsal to the 

 esophagus, and being intimately connected with the pleural 



