THE BATH SPONGE AND SOME ALLIES 287 



is muddy, sponges grow stalks that keep the mass away from 

 the mud, which if stirred up would smother the colony. 



Many marine sponges, being thick and massive, and of 

 loose texture, like the sulphur sponges, are very convenient 

 harbors of refuge for myriads of small animals, chiefly Crus- 

 tacea and worms. Undoubtedly the odor of living sponges, 

 described by one investigator as resembling garlic, drives 

 away fishes and other ravenous animals of large size that 

 might feed on the little guests, or even on the sponge itself. 



Economic Importance of Sponges. Some idea of the value 

 of sponges is gained from the fact that $715,000 worth of 

 sponges were sold in the chief sponge market at Tarpon 

 Springs, Florida, during the season of 1925. In some of the 

 shallow waters of the warm oceans, sponges are picked up 

 from the ocean floor with long-handled rakes and tongs. 

 Most of the market sponges are now gathered by divers 

 who can work in the deeper waters. 



Definition of Porifera (Lat. porus, " pore" ; ferre, "bear "). 

 By most investigators the sponges are considered a distinct 

 phylum, Porifera, including but a few classes (see page 307). 

 It is evident that the Porifera are lower in organization than 

 the Ccelenterata, for members of the phylum do not show 

 indications of muscle cells, of nerve cells, or of sense organs. 

 Neither are there special organs of offense. Protection is 

 afforded by the spicules and the characteristic odor. 



