CH. VI] 



THE NERVOUS SYSTEM 

 br 



121 



tn. 



Fig. 54. Nervous system of Petalura gigantea Leach ( x 2). ag^-agg abdominal 

 ganglia ; br brain ; cce circumoesophageal commissure ; 1 -n 10 segmental nerves 

 of abdomen; og optic ganglion; rn nerve to reproductive organs; sog sub- 

 oesophageal gangh'on; tg\-tg s thoracic ganglia; tn-^-tn^ segmental nerves of 

 thorax ; 1-10 limits of abdominal segments. Original, nitric acid preparation. 



