32 ANIMALS OF THE SEASHORE 



of the sea associated with the sponges. Great quanti- 

 ties of sponges can usually be seen drying on the 

 wharves. 



Although the large commercial sponges are 

 found only in warm seas, there are a number of 

 varieties that are found all along the east coast of 

 the United States. While these are mostly small and 

 of no commercial value, some are very beautiful. 



A few sponges have rather peculiar habits. The 

 Red Sponge (Microciona prolifera) is often found 

 growing on the back of Spider Crabs which use the 

 sponge as a camouflage. The Sulphur Sponge (Cliona 

 celata) bores into shells of oysters, clams and other 

 bivalves, and finally succeeds in killing the bivalve. 



Sponges have no regular mouths. Their bodies 

 contain a great number of small canals which finally 

 open again to the outside through larger openings 

 or oscula. These oscula are fairly conspicuous in 

 the ordinary Bath Sponge. Sea water is constantly 

 flowing through these canals, entering the sponge 

 through the small pores and leaving it through the 

 larger oscula. As this steady stream of water is 

 passing through the sponge, the small microscopic 

 plants and animals in the water are removed by the 

 sponge and utilized as food. 



The skeletal framework of sponges is composed 

 of a great many small fibers of a horny, calcareous 

 or silicious substance. These fibers are known as 

 spicules, and are very important in the classification 

 of the various species of sponges. 



