i8o 



s 5 



r.z* 



s.b 



FIG. 85. A very diagrammatic and generalized illustration of a complex ccelenterate 

 colony. The shaded portion represents the gastro-vascular cavity. The light portion, the 

 body tissues, b., a bell-like individual developed into an air-bladder; m., mouth; n.s., 

 nutritive individual; p.z., protective individual; r.s. 1 , r.z. 2 , r.s. 3 , different types of repro- 

 ductive individuals; s.b., swimming bell; t, tentacles, which are sensory and protec- 

 tive structures. After Lang. 



Questions on the figure. What is meant by "generalized" above? 

 How does such a polymorphic colony as this differ from a highly organ- 

 ized individual? In what respect is it similar to an individual? What is 

 the function of the gastro-vascular system? What is the gain in its wide 

 distribution through the colony? How do the siphonophora differ from 

 the other colonial ccelenterates ? 



