CHAETOPODA 



139 



Protodrilus Leuckartii is a small worm-like animal found 

 in the sand at Pantano, an inland arm of the sea in the neigh- 

 bourhood of Messina (Fig. 87). 

 It creeps about in a Nemertine- 

 like manner by means of the 

 cilia which clothe the body. 



The segmentation is shown 

 externally by two rows of ciha 

 on each segment, and by slight 

 grooves which separate neigh- 

 bouring segments from one 

 another. The number of the 

 segments increases with the 

 age of the animal. The head 

 bears a pair of hollow ciliated 

 tentacles, into which a section of 

 the coelom extends (Fig. 87). 



The ectoderm consists of 

 cubical epithelial cells, amongst 

 which the ducts of many uni- 

 cellular glands open. The cells 

 lining a shallow groove which 

 runs all along the ventral aspect 

 of the worm bear specially long 

 cilia. There is a double row 

 of cilia on the head in front of 

 the mouth, and an anterior and 

 a posterior circlet upon each 

 segment. Protodrilus, like Foly- 

 gordius, has no circular muscles ; 



the longitudinal fibres are FiB.87.~yievroi Protodrilus LeucTcartU. 

 arranged in four bands, two 

 dorso-lateral and two ventro- 

 lateral. An obhque longitudinal 

 muscular septum running from 

 each side of the body to near 

 the ventral median line divides the body-cavity into a median 

 and two lateral portions (Fig. 90). 



The alimentary canal consists of a ciliated oesophagus 



After Hatschek. 



1. Tentacle. 



2. Ciliated pit. 



3. Oral cavity. 



4. Muscular appendage of oral cavity. 



5. Alimentary canal. 



