The Soft Parts of tlie Fre§li-water Mussel 



Method of Examination. — If the animal be living, open 

 the shell as directed under the head of "Mollusc Shells." 

 Remove the right valve by cutting through the adductor 

 muscles at their points of attachment to the valve. Es- 

 amine the specimen in a dissecting-pan containing fifty 

 per cent, alcohol, which should be removed as often as 

 it becomes turbid. If freshly killed specimens be used, 

 the alcohol vrill coagulate the slimy excretion on the 

 surface of the body. This may be cleaned oif vs^ith a 

 camel's-hair brush. 



External Anatomy, 

 a. The relation bet^wreen the body and the shell. — 



Does the body fill the shell? Is it in contact 

 v^dth the shell at all points ? "What holds it in 

 place? Does it have the same shape as the shell? 

 How do you distinguish the anterior end of the 

 body? 



l. The palliura or mantle. — "Why is it so called? "What 

 is its shape? How many lobes or folds has it ? Are 

 they connected ? If so, where ? Do they corre- 

 spond in size and shape with the valves of the 

 shell? "Where is the mantle attached to the shell? 

 "Where to the body ? "What is its texture ? Color % 

 Do you find any variations in either? To what 

 are such variations due? Notice a thickened 

 band, the pallial muscle, near the margin. 



