Flatworms and Roundworms 369 



the anterior and posterior ends of the body (Fig. 177). The intestine 

 joins the pharynx and has one anterior and two posterior main branches, 

 each with numerouSj smaller^ lateral branches or diverticula (di ver -tik' 

 ula) (L. de, d^Mdiy; vertere, to turn). The intestine serves as a gastro- 

 vascular cavity (gas tro -vas' ku lar) (Gr. gaster, stomach or digestive; 

 L. vasculum, vessel or circulatory) in which both digestion and circula- 

 tion take place. The pharynx may be everted and protruded through the 

 ventral surface as a tubular proboscis (pro -bos' is) (Gr. proboskis. 



Transverse tube 



Excretory tube 



Labera] branches 



Excretory pore — 



Anterior wbestine 



with lateral branches 



Pharynx 



flame cell with cilia. 

 to propel wastes 



-Opentna of pharynx. 

 _>Moafch 



.Posterior 

 intestine 



Flame eel ( 



(enlarged) 



Fig. 177. — Planaria of the phylum Platyhelminthes, class Turhellaria, showing the 

 digestive system, A, and the excretory system, B. 



trunk) when feeding. Part of the foods are digested within the intestine 

 by digestive juices secreted by cells which line it. This is called extra- 

 cellular digestion (outside of cells). Other foods are digested by diges- 

 tive juices within food vacuoles within these cells. This is called intra- 

 cellular digestion (within cells). There is no anus, and wastes are elimi- 

 nated through the mouth, which is a rather common practice in many 

 lower animals. 



