3io 



Descriptive Zoology. 



turb the sponge, these smaller openings would close, and 

 perhaps the larger ones also. If he now tried to pick it 

 up, it would be found firmly attached. Effort to detach 

 it by pulling would probably crush it, and show that the 

 whole has about the consistency of beef liver. It is easy 

 to squeeze out all of the soft tissue and leave the elastic 

 skeleton. 



Source of Commercial Sponges. The most valuable of the 

 sponges of commerce come from the Mediterranean ; many 

 also come from the Red Sea, Florida, and the West Indies. 



Water 

 Exit 



FIG. 178. DIAGRAM OF A COMMERCIAL SPONGE. 



Collecting Sponges. Sponges are collected by divers, or 

 by the use of rakes, or by dragging hooks. They are piled 

 on shore to allow the soft tissues to decay, after which 

 they are washed, dried, sorted, trimmed, and shipped to 

 market. The finer ones are usually bleached. Sometimes, 

 in trimming away the base where they are attached to 

 the rock, enough is cut away to leave a large hole ; this 

 is the lower end of the cloaca, or main cavity. 



Fresh-water Sponges. Most of the sponges are marine, 

 but there is one family of sponges in fresh water. It is 

 not uncommon to find them in lakes and rivers, where they 



