A Cephalophorons Mollusk. 67 



tractors of the proboscis and midway between the large yel- 

 low salivary glands. The ducts from the salivary glands 

 appear as two delicate tubes extending one on either side of 

 the oesophagus as it passes down the proboscis. 



Draw. 



At a short distance beyond the salivary glands the oesoph- 

 agus is surrounded by the orange-colored ganglia of the ner- 

 vous system. A little posterior to the oesophageal nerve- 

 ring, the alimentary tube receives the duct from a delicate, 

 elongated gland, the "pancreas" which lies to the right side 

 of and upon an enlarged section of the alimentary tract, the 

 crop. The crop becomes smaller in diameter as it ap- 

 proaches the liver, into the lower portion of which it courses, 

 and becoming again enlarged, forms the " stomach." The 

 walls of the stomach may be seen without dissection as a 

 whitish tract on the outer surface of the liver. 



If the stomach is opened and the contents washed away, 

 the large hepatic ducts will be found. How many ducts are 

 there ? After passing along the lower side of the liver, the 

 stomach bends abruptly upward and forward, and thence, as 

 the intestine and rectum, runs to its external opening parallel 

 to the crop and oesophagus. Is the epithelial lining of the 

 rectum in any way specialized ? 



Make drawings that will illustrate the course of the ali- 

 mentary tract. 



(e) The Nervous System. The nervous system of the 

 Cephalophorous or Gasteropod mollusks consists of a series 

 of ganglia, chiefly arranged around the oesophagus, and of a 

 number of radiating nerve-cords. The circle of ganglia sur- 

 round the oesophagus somewhat in front of the duct of the 

 " pancreatic gland," and when viewed from above present 



