THE CLAM. 101 



of which is the dark-green liver* Trace the oesophagus 

 from the stomach to the mouth. 



Take a clam which has been hardened for a couple of 

 weeks in strong alcohol or formol. Cut it transversely in 



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slices a quarter of an inch thick, using a sharp scalpel for 

 the purpose. Draw the sections and name all the parts 

 found. This can be done easily if the previous dissectiqri 

 has been intelligently done. 



In the shell which has been removed make out the fol- 

 lowing points on the inner surface. Near the dorsal line 

 the scars formed bv the two adductor muscles, and close to 



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the posterior scar smaller scars produced by muscles which 

 retract the foot. Following the free margin of the shell 

 from the anterior adductor scar, downwards and backwards 

 towards the posterior adductor, a pallial line, caused by 

 the thickened edge of the mantle. Does this continue 

 parallel to the margin all the distance or does it extend 

 inwards towards the centre of the shell, forming a large 

 bay (pallial sinus)'? If the latter be present determine 

 what causes it. 



Examine these points in other bivalve shells. Could 

 one tell by an examination of the shell whether one or two 

 adductors were present, the relative size of the foot, the 

 presence of a well-developed siphon, etc.? 



* In a pocket of the stomach in the long clam will be found a 

 structure of unknown function, the crystalline style, transparent, 

 an inch or more in length. 



