no 



THE SPONGES— PHYLUM PORIFERA 



sit down while a moving belt carries the food past them and they reach 

 out and help themselves to that which appeals to them. The cells which 

 bear the flagella have a collar around the base of the flagellum so that, 

 in beating, the flagellum will not drive away food particles which the cell 

 needs to ingest. These are called collar cells because of this character- 

 istic. Digestion is still intracellular as in the protozoa, and in egestion 

 the cells expel the residue into the water flowing past, so that the entire 



Courtesy General Biological Supply House 

 Fig. 8.1. A cluster of scypha. New individuals arise from old through budding; thus 

 eventually a large cluster of these sponges may be found in one spot. 



process is still very much the same as in amoeba. With all this taking 

 place, you can see that the sponge is really a very active animal after all, 

 and a sponge only an inch or so long can draw as many as 45 gallons of 

 water through its system in a single day. 



Respiration is still by direct absorption of oxygen from the water by 

 the cells and the giving off of carbon dioxide into the water as it flows 

 past. Excretion follows the same pattern as each cell gives off these 

 wastes into the convenient sewage system flowing past it. The excretory 



