BUSYCON 149 



side, are three pairs of slender muscles, one pair median and 

 the others covering the horns of the odontophoral cartilage 

 that has just been observed. Find to what the muscles are 

 attached anteriorly and posteriorly. If the animal is fresh, 

 pull on the muscles or stimulate the nerves by pinching gently 

 with forceps and see what moves. These are the radula 

 protractors. 



(d) Beneath the radula protractors observe the sheet of 

 cross fibers that bind the horns of the odontophoral cartilage 

 together. 



Make a drawing showing the ventral side of the buccal 



mass. 



(e) A portion of the radula is visible near the anterior 

 end of the proboscis. Introduce a bristle into the esophagus 

 and determine its relation to the exposed radula. 



(/) Loosen the anterior end of the buccal mass from the 

 wall of the proboscis, turn it back and see how the radula 

 passes around the odontophoral cartilage. With a hand lens 

 notice the teeth on the open radula, ventral to the cartilage, 

 and see how the radula is folded as it passes over the dorsal 

 side of the cartilage so the teeth are turned in. What func- 

 tion does this serve? 



(g) Cut the cartilage protractors and reflect the buccal 

 mass. It is attached to the wall of the proboscis at its pos- 

 terior end by strong muscles, the radula retractors. These 

 may be studied after cutting the sheath of cross fibers that 

 hold the mass together. Determine how they are attached to 

 the sides of the radula. Why do they need to be so powerful? 



Make a drawing oj the buccal mass as seen from the 

 dorsal side. 



(h) Pull away the muscles and examine the shape of the 

 odontophoral cartilage and its relation to the radula. 



(i) Remove the radula, unfold it, and examine it micro- 

 scopically. Do the teeth differ in any way at the two ends? 

 Why is the radula so long? 



Draw a portion. 



