252 



METAZOAN PHYLA 



Anfennule 



An fen net 



Opening of 

 green gland 



Third 

 maxitliped 



swimmerets 

 Swimmerets 



Uropod 



Telson' Anus 



Fig. 152. — Under side of Cambarus virilis Hagcn, a common species in the central states. 

 From a male specimen from Wisconsin. X %. 



Musc/es 



Heart 

 Pericardium 

 Vas deferens 



Sternal artery 



Oill 

 chamber 



Oill 



Ventral 

 thoracic artery 



Ventral nerve 



cord 



Muscles 

 of leg 



Fig. 153. — Diagrammatic cross section through a crayfish (Cambarus) in the posterior part 

 of the cephalothorax, to show the gill chambers and gills. 



