598 



INVERTEBRATE MORPHOLOQT. 



are traversed, except towards the extremities of the lateral 

 tubes where the individuals occur, by a chitinous rod which 

 results from the chitinization of what was once the stem of the 

 various polyps. Each of these is stalked (Fig. 272), the stalk 

 {G) becoming continuous below with the chitinous rod, and 



Fia. 372. — Individual of Rhabdopleura (slightly modified after Lankkstke). 

 (N.B. — The tentacles of one side of one arm only are represented.) 



B = anal papilla. O = tentacle. 



= stalk. Oa = arm. 



D = epistome. I = intestine. 



E = trunk region. K = sensory papilla. 



F = collar region. iV = notochord. 



each consists of three well-marked regions. What may be 

 termed the anterior portion of the body is formed by a large 

 disklike epistome {D), beneath which on the ventral surface is. 



