A Cephalophorous filollusk. 65 



of the ovary and passes down to the nidamental gland. In 

 the living animal it rests against the columella. Follow the 

 course through the lumen of the nidamental gland to the 

 exterior. Open the ovary and note the ultimate branches of 

 the oviduct and the numerous eggs. 



Make drawings that will illustrate the anatomy of the 

 ovary and the course of the oviduct. 



The testis of the male lies in the same place as does the 

 ovary of the female, and its duct, the vas deferens, pursues a 

 similar course along the inner surface of the liver to that 

 taken by the oviduct. The course along the floor of the 

 mantle chamber has already been noted. 



Draw. 



(</) The Digestive System. Select a specimen that has 

 been killed while the proboscis remained protruded and 

 note the terminal mouth-opening, and the lingual ribbon or 

 odontophore, projecting slightly from its lower side. With a 

 pair of scissors slit open the proboscis along its mid-dorsal 

 line, taking care to cut only through the skin. Immediately 

 below the incision, the light-colored (Esophagus will be seen 

 as a straight tube. It extends from its opening into the 

 pharyngeal cavity, immediately over the end of the odonto- 

 phore, to the upper end of the proboscis, where it abruptly 

 dips into the substance of the body. Note the small fibres 

 that attach it to the integument, and which, at its outer end, 

 are deeply colored, and may, by their contractility, give the 

 organ a pumping function. Extending from the base of the 

 proboscis into the substance of the body are a pair of white 

 muscle bundles, the right and left retractors of the proboscis. 



Below the oesophagus lies the deep-colored muscular mass 

 that brings about the movement of the lingual ribbon. 



