48 ELEMENTARY BIOLOGY. [CHAP. 



canal, at that point at which it receives the urino- 

 genital ducts. 



Examine its lining membrane ; it is for the most 

 part identical with that of the large intestine ; that 

 of its terminal third has the characters of the inte- 

 gument. 



b. The ureters (urinogenital ducts $ . Cf. Sect. F. 3); 

 their openings will be seen as two minute orifices, 

 on the dorsal wall of a., situated close together and 

 surrounded by tumid lips. 



c. The bladder ; a median ventral diverticulum of a., 

 having no direct communication with the ureters. 



E. The cavity of the mouth and the respiratory organs. 



i. Use the specimen dissected above. Cut the ali- 

 mentary canal across immediately in front of the 

 liver, and retain the anterior portion. Pin down 

 under water ventral surface uppermost enlarge the 

 mouth opening by cutting through the sides of the 

 buccal cavity with a pair of scissors : pull down the 

 lower jaw and pin it back. 



a. The two internal openings of the nasal cavities 

 (posterior nares); near the anterior end of the roof 

 of the mouth. 



b. The openings of the Eustachian recesses; situated 

 far back near the angles of the jaw. 



c. The teeth; confined to the upper jaw and roof of 

 the mouth. 



a. The maxillary teeth; forming a parallel series, 

 set along the inner face of the whole upper jaw. 



