PHYLUM PLATYHELMINTHES 



237 



a short mouth-cavity into a cylindrical thick-walled chamber, the 

 pharynx (ph.), which is highly mobile, and is capable of being 

 thrust out as a proboscis through the mouth, beyond which it 



FIG. 1S2. Planaria. Digestive and excre- 

 tory systems, f?. openings of excretory 

 system ; int. intestine ; mo. mouth ; 

 o. ph. opening of pharynx. (After Jijinm 

 and Hatschek.) 



FIG. 1 S3. Planaria. Nervous system. 

 br. brain ; eye, eye ; I. ne. longitu- 

 dinal nerve ; pit. pharynx. (After 

 Jijima and Hatschek.) 



may then be extended to a relatively considerable distance. 

 When retracted it lies within an enclosing muscular sheath. The 



