150 MOLLUSC A 



5. In a living Busy con removed from its shell and par- 

 tially anesthetized (by the addition of chloroform to the sea 

 water), observe the activity of the radula. Any student 

 who has already completed the dissection of the radula in 

 the injected specimen may make a special dissection of the 

 odontophoral apparatus, utilizing this fresh material. Fol- 

 low directions as given in section 4, page 148. After exposing 

 the various muscles and nerves these may be stimulated by 

 pinching gently with forceps or by pulling the muscles. In 

 this way a clear idea of the function of the muscles may be 

 obtained. 



The radula is the organ upon which most gastropods de- 

 pend for getting food. You should understand how: 



1. The proboscis is protruded and retracted. 



2. The odontophoral cartilage is protruded and retracted. 



3. The radula is protracted and retracted. By means of 

 a binocular dissecting microscope note its action in a living 

 crepidula. 



4. The radula is folded by the cartilage and spread for 

 action. 



5. The food is torn off and taken into the mouth. 

 Near the base of the proboscis is a pair of large, yellow 



salivary glands, the ducts from which extend on either side of 

 the esophagus to the mouth. Further back, on the right side 

 of the esophagus, is the small pancreas. 



After studying the nervous system, trace the esophagus 

 to the stomach and the intestine to the anus. 



Nervous System. — Most of the ganglia are grouped around 

 the esophagus, about three quarters of an inch posterior to 

 the base of the proboscis. They are all brown and accord- 

 ingly conspicuous. Carefully cut around its base so the pro- 

 boscis may be turned back, and the ganglia on the ventral 

 surface of the esophagus may be seen. Carefully pick away 

 the tissue that covers the ganglia and notice on the ventral 

 side of the esophagus: 



1. The small but conspicuous buccal ganglia. These are 



