THE TAPEWORM 99 



duction also occurs by fission. If dividing specimens are found in the 

 laboratory, compare the regeneration following fission with the regen- 

 eration following artificial cutting. 



THE FLUKEWORM 

 Exercise 1. — Structure of the Adult. 



(a) The platyhelminths of the Class Trematoda are the external 

 and internal parasites known as flukes, or flukeworms. For this study, 

 specimens of the Genus Pneumonoeces, from the lungs of the frog, or 

 of the Genus Clinostomum, which is found in a somewhat immature 

 condition encysted in the coelomic region of the frog, are excellent 

 material. 



(b) Examine living or preserved specimens and locate the mouth 

 and suckers. How do the shape and behavior, if specimens are ob- 

 served alive, compare with the same in the planarian? Locate the 

 digestive tract and compare with that of the planarian. The repro- 

 ductive organs are complex and of varied appearance in the different 

 genera of flukes. If they are studied, special directions will be given 

 by your instructor. The animals are hermaphroditic; zygotes, sur- 

 rounded by yolk cells and an eggshell, accumulate in a terminal por- 

 tion of the female organs, the uterus, and develop later when they are 

 laid. The life-cycle is greatly complicated in correlation with the 

 parasitic habits; understand from lectures or textbook. Make a 

 figure (X 10), showing the features above noted. 



THE TAPEWORM 



Exercise 1. — External Features of the Adult. 



(a) The platyhelminths of the Class Cestoda are known as tape- 

 worms. They are parasitic forms, even more highly modified in 

 relation to their parasitic habits than the flukes. The adults occur as 

 parasites within the digestive tract of some vertebrate known as the 

 primary host; the larval stages occur mostly within the tissues of a 

 secondary host, upon which the primary host is likely to feed. Species 

 of the Genus Taenia are found in many common mammals. Taenia 

 pisiformis, w'hich has the dog for its primary host and the rabbit for 

 its secondary host, is excellent material for this study. Specimens may 

 be examined alive in water, or after preservation in formalin. 



(b) Examine the adult cestode in a pan of water. The smaller 

 end has an enlargement, the scolex; the larger end has mature pro- 

 glottids, as the segments composing most of the body are called. What 



