A LAND SNAIL 99 



seminis, a small, spherical body the size of a small shot, at the 

 end of a long tube, will be found in a bend of the intestine, from 

 which it must be separated. 



We turn now to the other end of the intestine. Trace the rec- 

 tum from the anus to the point where it is surrounded by the 

 liver and carefully dissect away the integument which covers the 

 inner surface of the whorl. The light-colored hermaphroditic 

 gland will be exposed. Then remove the delicate integument 

 which covers the outer surface of the whorl, and the dark-brown 

 liver will be exposed. Press the liver away from the intestine and 

 completely free it, being careful not to break either liver or in- 

 testine. Great care should also be taken not to injure the her- 

 maphroditic gland, which is the yellowish mass on the inner side 

 of the last whorl, or the hermaphroditic duct leading away from 

 it. Note that the liver is composed of two masses, the smaller 

 of which is of spiral form and occupies the apex of the shell ; the 

 larger is subdivided into three lobes. Note also the two main 

 bile ducts which join the liver with the intestine. The visceral 

 artery will be seen lying upon the liver, sending branches off on 

 both sides, and must not be confused with the bile ducts, which it 

 resembles in appearance. It carries blood from the aorta to the 

 top of the spiral, supplying all the organs of the visceral mass. At 

 the point where the bile ducts communicate with the intestine, 

 that organ makes a sharp turn. 



Spread out the digestive tract to the animal's left and pin it 

 down, without removing or breaking the hermaphroditic gland 

 or duct. The stomach will be seen to extend nearly to the liver. 

 Next comes the intestine, which soon makes the sharp turn above 

 mentioned, receives the bile ducts, and passes into the rectum 

 at the right side of the mantle cavity. 



Exercise 5. Draw an outline of the alimentary tract from the mouth 

 to the anus on a scale of 2 and label all its parts. 



Study the structure of the pharynx. Pass a probe into the 

 mouth and notice the extent of the pharyngeal cavity . Notice the 

 transverse, horny jaw in the roof of the mouth. With a sharp 

 knife split the dorsal pharyngeal wall, taking care not to injure 



