156 ANIMAL ACTIVITIES. 
introduced by a pipette. What do you learn from this 
concerning the manner of feeding ? 
What happens when you touch the animal on its 
shell and at different places on its fleshy parts when it 
is feeding quietly ? 
Examine a mussel or clam which has been boiled, 
or hardened in alcohol. 
Press the valves together and quickly release them. 
Why do they fly open again ? 
When the mussel was alive what held the valves 
together? Explain the manner of opening and closing 
the shell. 
Place the mussel on its side in a dish of water so that 
the dorsal portion is away from you. Is the anterior 
portion of the mussel near your right hand, or your left 
hand ? 
Carefully remove the upper valve without disturbing 
the soft parts beneath. Have you removed the right 
or left valve ? 
The membrane lining the interior of the shell is the 
mantle which secretes the material of which the shell 
is formed. Does this mantle line the entire shell? Is 
it of equal thickness in all parts? 
How many muscles held the valves together ? 
On a dry shell do you find the marks which show 
where the muscles were attached? Do you find the 
muscles themselves ? 
Determine which is the posterior adductor muscle and 
which is the anterior adductor muscle. 
Find the mark which the mantle makes where it 
adheres to the inside of the shell. Call it the pal/al 
line. Do you find any other markings on the inside of 
the shell? Compare mantle outside of pallial line 
with that above. What is the relation of mantle to 
shell ? 
Raise the mantle and notice the striated leaf-like 
gills. How many do you find ? 
Look for the Jabial palps near the anterior portion 
