192 



function. It consists usually of one pair, sonaetimes two pairs of very 

 small funnels, lying in the posterior part of the sixth segment, against 

 the muscular layer, in an extremely dorsal position (Fig. 2). 



Each of these funnels ends in a very thin tube which passes 

 through the muscular coat. 



But, instead of opening directly and freely on the epidermic sur- 

 face, these tubes fall into a longitudinal duct which runs forward and 

 opens, through a tiny pore, at the other end of the sixth segment 

 (Fig. 1 and 2). 



This duct is a merely epithelial structure; it lies outside of the 

 thick basal membrane, within the epiderm itself. Being thus super- 



Fig. 1. 



Fig. 3. 



Fig. 2. 



Fig. 4. 



Fig. 5. 



Fig. 1. Fore part of Owenia projecting out of the sandy tube; dorsal view. The 

 two epidermic ducts appear as a darli sinuous line on the sixth segment. 



Fig. 2. Schf matic longitudinal section through the body wall, showing the relations 

 between the funnels and the epidermic duct. 



Fig. 3, 4 and 5. Transverse sections of the epidermic duct showing its superficial 

 situation and the peculiar disposition of the cells. In Fig. 3 the] duct is transformed 

 into an open groove. 



