A LAND SNAIL 119 



the inner surface of the whorl. The light-colored hermaphroditic 

 gland will be exposed. Remove, then, 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, without, however, breaking either liver 

 or intestine. Great care should also be taken not to injure the 

 hermaphroditic 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, however, removing or breaking the hermaph- 

 roditic gland or duct. The stomach will be seen to extend 

 nearly to the liver. It is succeeded by 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. 



tudy 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 



1 sharp knife split the dorsal pharyngeal wall, taking care not to 



