FEESH-WATEE MUSSEL 201 



posterior adductor muscle, to the gills, and to the 

 pallial lobes and connectives, already partially 

 traced, running to the cerebral ganglia. 



c. The pedal ganglia — Very careful dissection will 

 be needed to show these. They lie in the middle 

 line of the foot, close to the point where the foot 

 and the abdomen join, and about one-third of the 

 length of the former organ from its anterior end. 

 Compare these ganglia with the others studied, 

 and try to trace the connectives running to the 

 cerebral ganglia. Look for the pair of otocysts, 

 or " ear," a short distance behind and below the 

 pedal ganglia. 

 Make a diagram showing the position of all of the 

 ganglia and the course of the nerves. 



D. — The Excretory System. 



Lying under the pericardium, extending for- 

 ward from the posterior adductor muscle, find on 

 each side a wide, dark-colored tube with spongy 

 walls. Endeavor to make out the lower portion 

 of the tube with its folded spongy walls, the 

 " kidney," or organ of Bojanus, and a thin- 

 walled conducting tube, the "ureter." Look 

 for the opening of the latter into the anterior 

 end of the pericardium. Pass a bristle from 

 the pericardium into the organ of Bojanus. 

 Opening into the cloacal chamber immediately 

 below and behind the anterior end of the peri- 

 cardium look for a small pore, the renal ap- 

 erture or external orifice of the "kidney." 

 Near the renal aperture look for the genital 

 aperture. 



