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TEXTBOOK OF ZOOLOGY 



which extends through about six segments and which has a digestive 

 gland opening into it from both sides. The remainder of the diges- 

 tive tract is a straight intestine which continues to the last segment, 

 where it opens to the outside. 



Prostomlum 



Prostomlal 

 tentacles 



Feristomlal 

 tentacles 



Parapodia 



Pharynx 



CEsophageal 

 glands 



(Esophagus 



Intestine 



Nephrldla 



Dorsal vessel 



Ventral 

 vessels 



Nerye-cord' 



Fig-. 101. — Internal anatomy of Nereis virens. (From Hegner, College Zoology, 

 published by The Macmillan Company, after Parker and Haswell.) 



The circulatory system is composed principally of a dorsal and a 

 ventral blood vessel joined in each segment by a pair of connecting 

 vessels. The blood is forced anteriorly through the dorsal vessel and 



