opt. I 

 opt.n. 



an.com 



Ltr.com. 



Fig. 199. A plan of the nervous system of Chirocephalus . ab.z, second ab- 

 dominal somite ; an.' antennulary nerve ; an." antennary nerve ; an." com. com- 

 missure for fibres which unite antennary ganglia; hrn. brain; fr. nerve to 

 frontal organ; ga. ganglion of ventral cord; m.e. nerves to median eye; 77id. 

 mandibular nerve; mx.' maxillulary nerve; wjc." maxillary nerve; oe. oeso- 

 phagus; oe.com. circumoesophageal commissure; opt.l. optic lobes; opt.n. 

 optic nerve; th. i, first thoracic somite; th. 12, nerve of last thoracic somite; 

 tr.com. transverse commissure of ventral cords. 



18-2 



