g^.2 



V^7- 



gtuG 



Fig. 25.— Astacns fliiviatiUs.— The central nervous system seen from 

 above (nat. size), a, vent ; an, antennary nerve ; a'71, antennulary 

 nerve; <?, circumcesophageal commissures ; ffti. 1, supracesophageal 

 ganglion ; gn. 2, infraoesophageal ganglion ; gti. fi, fifth thoi acic 

 ganglion ; ffn. 7, last thoracic ganglion ; (/n. 13, last abdominal gang- 

 lion ; ces, oesophagus in cross section; oti, optic nerve; sa, sternal 

 artery in cross section ; sf/n, stomatogastric nerve. 



