i 7 6 



ELEMENTARY ZOOLOGY. 



s b 



s.b 



r.z: 



P-z. 



FIG. 48. A very diagrammatic illustration of a complex coelenterate 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; nt, mouth; w.z., nutritive 

 individual; p.z., protective individual; r.z. 1 - 3 , different types of reproductive individ- 

 uals; s.b., swimming bell; t, tentacles, which are sensory and protective structures. 

 After Lang. 



Questions on the Figure. What shows that this is a colony rather 

 than a complex individual? In what respects is it similar to an 

 individual? What is the function of the gastro-vascular system? 

 How do the Siphonophora differ from the other colonial ccelenterates ? 



