10 



GUIDE TO THE STUDY 



tive of the genus Polystomum from frogs or turtles. Note the six 

 posterior suckers, the small hooks, and the two large hooks, the 

 branched alimentary canal, and the short uterus containing a 

 single egg. Make a sketch showing these points. 



Clonorchis sinensis, the Asiatic liver fluke of man, or a 

 related species will be taken as a representative of the digenetic 

 flukes. Study under low power the prepared slide furnished and 

 note the following features: 



oral sucAer 



oesophagus 



raj deferent 



orart/. 

 peceptacufam semmjs 



•ZaurtrS canal 

 /vcaptaculum seminis 



Fig. 3.' — Anatomy of a trematodo, Opisthcrchis viverrina. (Barker, after Poiricr.) 



External Characters. — Shape and size. Is the cuticle smooth 

 or spinose? (In order to determine this, cut down the iris 

 diaphragm of your microscope and examine the margins of your 

 specimen.) What is the number, position, and relative size of 

 the suckers? What is their relation to the mouth? Close to 

 the median anterior margin of the ventral sucker is the genital 

 pore, the common outlet of the male and female organs. Locate 

 the excretory pore at the caudal tip of the body. 



Alimentary Canal. — Distinguish the mouth, the muscular 

 pharynx, the short, unbranched oesophagus, and the two branches, 

 or intestinal rami. How far caudad do these rami extend? 

 Do they exhibit lateral branches, or diverticula? Is there an 

 anus present? 



Reproductive System. — As in the great majority of flukes, 

 Clonorchis is hermaphroditic; that is, both male and female 

 organs are found in the one individual. 



