THE SPONGES— PHYLUM PORIFERA 



115 



tages ; yet, because of the specialization of the cells, the metazoan is 

 doomed to death as these cells grow old and die. On the other hand, 

 the protozoan is potentially immortal even though death may come 

 often due to various circumstances which can destroy it. In the 



Photos by Winchester 



Fig. 8.4. Sponges grow in many different shapes and sizes. These are: Top row — 

 grass sponge, Spongia dura, and finger sponge. Middle row — tube sponge, sheep wool 

 sponge, and Venus flower basket. Bottom row — paper sponge, and crumbs of bread 



sponge. 



