THE OYSTER. 



Oysters in the shell should be used. Find the hinge as 

 in the clam. Do you find lines of growth? In the same 

 way as in the clam distinguish anterior and posterior, right 

 and left valves. Is the right or the left valve convex? 



Break the shell at the hinder end and, inserting a knife, 

 cut the adductor muscle so as to remove the left valve.* 

 How many adductors do you find? Is the mantle edge 

 thickened and united as in the clam? Do you find any 

 siphons? What other peculiarities do you find in the edge 

 of the mantle? 



Remove the mantle from the left side and trace the parts. 

 How does the foot compare with that of the clam? How 

 do the palpi differ? How many gills? Which adductor 

 anterior or posterior is absent? Find the heart, just in 

 front of the adductor. Lay open the pericardium. How 

 many auricles and how many ventricles are present? 

 Trace the alimentary canal through the body from the 

 mouth to the vent. How is it related to the heart? 



* If you do not know where the adductor is, study a shell already 

 removed and find the scar made by it. 



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