FRESH- WATER MUSSEL. 65 



I. Through the pedal ganglia. 



Find the stomach, digestive gland, labial palps, 

 foot, and mantle. 



II. Through the heart. 



Find the ventricle, the rectum with the typh- 

 losole, auricles, organ of Bojanus on each 

 side with the vena cava between, the vis- 

 ceral mass with the intestine cut through 

 in a number of places, the reproductive 

 organ filling up the greater part of the 

 visceral mass, the foot, the inner and outer 

 gills, the suprabranchial chamber dorsal 

 to the outer gill on each side, the branchial 

 chamber, the mantle. 



III. Through the visceral ganglia. 



Find the rectum, the posterior adductor 

 muscle, the visceral ganglia, the divisions 

 of the suprabranchial chamber (how 

 many ?), the branchial chamber, the mantle. 

 Diagram of these three sections ! 

 In the other sections trace the organs from 

 section to section. 



