8o PHYLUM MOLLUSCA 



missure. Each ganglion sends out three large nerves : the 

 cerebrovisceral connective, which goes to the visceral ganglia, the 

 cerebropedal connective, which goes to the pedal ganglia, and 

 the pallial nerve, which passes to the mantle. Find them. 



The pedal ganglia form a nervous mass buried in the foot near 

 its base. Make a shallow longitudinal incision in the bottom of 

 the foot and gently pull the flaps apart ; the pinkish mass and the 

 nerves radiating from it will be seen. 



Exercise 10. Draw a diagram representing the nervous system. 



Make several transverse sections with a razor through the 

 region of the heart of a clam which has been previously hard- 

 ened. Identify all the organs which appear. 



Exercise 11. Draw a diagram representing a cross section ; carefully 

 label all the organs. 



