56 HELMINTHOLOGY 



d. Examine the buccal cavity of the specimen for jaws. What is 

 the arrangement of the jaws? Some leeches do not possess jaws. 



D. Examine a specimen of the medicinal leech, Hirudo 

 medicinalis. 



a. Examine the jaws for teeth. 



b. What is the color of the specimen, noting longitudinal 

 striping? 



Draw the specimen. 



E. If available examine and describe a specimen of the horse 

 leech, Hcemopis sanguisuga. 



EXERCISE 31 



THE SHEEP LIVER FLUKE DISTOMUM HEPATICUM 



ORDER PLATYHELMINTHES, CLASS TREMATODA, ORDER MALACOCO- 

 TYLEA, FAMILY FASCIOLID.E 



A. Characteristics of Platyhelminthes. Body more or less 

 flattened dorso-ventrally; alimentary canal, absent entirely in 

 the tapeworms, consists of a blind sac more or less branched. 

 No anus. Usually hermaphroditic, and development in the 

 parasitic species is usually indirect, i. e. through an intermediary 

 host. The phylum is divided into three classes: i, Turbellaria, 

 free living, non-parasitic; 2, Trematoda, flukes; and 3, Cestoda, 

 tapeworms. 



B. Characteristics of Trematoda. Usually leaf-shaped, but in 

 a few species conical; sucking discs are commonly found on the 

 anterior and posterior extremities, and the ventral surface. 

 Mouth is at anterior end, and sexual openings in the ventral 

 sucker. 



C. Characteristics of Fasciolida. One oral and one ventral 

 sucker; excretory pore discharges at posterior border. 



D. Distomum (Fasciola) hepaticum. This liver fluke in- 



