166 



METAZOAN PHYLA 



(Fig. 76), a fluke which h-ves as an adult in the bile ducts of the Hver of 

 man, dog, and cat, and is found in China and Japan. In addition to 

 the firm leathery cuticle, the absence of ciha, and the presence of suckers, 

 all of which represent adaptations to a parasitic mode of existence, this 

 form in its adult condition is to be contrasted with a planarian in the 

 absence of eyespots and in the more highly developed reproductive 

 system. The single excretory pore lies at the extreme posterior end of 



-Oral sucker 

 -P/iaryrJx 



-Merye center 



Gen/ta/ 

 pore 



Excrefory. 



5emjr7a/ 

 receptarc/e 



Laurer's 



Testes 



Erjterort 

 Van trof/ sucker" 



Yolk gr/air)fifS 



- Vas deferens 

 Uterus 



—Yolk of act 

 Ovary 



Vas effererjs 



fxcretory 

 pore 



Fig. 76. — Clonorchis sinensis Cobbold. {Rcdraum from Hegnrr, Root and Augvstine, 

 ^'Animal Parasitology, ''' after Faust.) Dorsal view, showing internal structure. X 8. 



the body. Added to the female organs is a shell gland which secretes a 

 substance that hardens the shells of the eggs (Fig. 77). 



194. Cestoda. — This class includes the tapeworms, which are most 

 common in the alimentary canals of vertebrates. A typical tapeworm 

 (Fig. 78) consists of a more or less rounded head, or scolex, and a relatively 

 slender neck, which together form one section of the body, and a number 

 of other sections called proglottids. The scolex bears suckers and is 

 projected at its free end into a rostellum which may have an encircling 



