RHABDOPLEURA. 



Ill 



teriorly placed. The tube is secreted by the buccal discs of the 

 zooid. It consists of a series of rings, each of which is secreted 

 separately by the buccal disc and added to its predecessor. It is 

 therefore quite independent of and separate from the bodies and 



FIG. 81. Rhabdopleura nor- 

 mani from the right side 

 (after Lankester, from 

 Lang). 1 buccal disc (pro- 

 boscis) ; 2 arms with ten- 

 tacles ; 3 region of the 

 collar pore ; 4 anus ; 5 

 trunk ; 6 stalk or pedicle. 



stalks of the zooids, and the body of the animal can move freely 

 within its tube. It can be retracted into the tube by the con- 

 traction (into a spiral) of a muscle in the stalk, and it can crawl 

 up the inside of its tube by help of its buccal disc and can protrude 

 its arms from the terminal opening. 



