TREMATODA. 



381 



sucker or disk, and has around it three jaws in the posi- 

 tion of radii, and each of the jaws is armed with two 

 rows of minute teeth, and the jaws are so worked by 

 muscles that a sort of sawing movement is given to each 

 jaw separately. 



SUB-SECTION VII. 

 THE ORDER OF TREMATODA OR FLUKES. 



THE worms of this group are more or less elliptical 

 or oval, and flattened ; and are parasitic in their habits, 

 being found in the liver of sheep, and of man, and of 

 other animals. The name is from the Greek trema, a 



FIG. 516. 



7 



i 



Lever Fluke, FascioJa hepatica, Linn. 

 m, month: .s, sucker; ff, genital orifices; i, intestinal tubes. 



hole ; the Trematods have a branching digestive sys- 

 tem, to which there is only one opening the mouth. 

 They generally have one or more sucking disks, by 

 means of which they adhere to other animals. 



