CHAETOPODA 139 
Protodrilus Leuckartit 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 cilia 
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 Poly- 
gordius, has no circular muscles ; 
the longitudinal fibres are yg, 87.—View of Protodrilus Leuckartti. 
arranged in four bands, two 
dorso-lateral and two ventro- 
lateral. An oblique longitudinal 
muscular septum running from 
each side of the body to near 
the ventral median line divides the 
and two lateral portions (Fig. 90). 
The alimentary canal consists 
oe eh 
After Hatschek. 
Tentacle. 
Ciliated pit. 
Oral cavity. 
Muscular appendage of oral cavity. 
Alimentary canal. 
body-cavity into a median 
of a ciliated oesophagus 
