THE BOOK ABOUT THE SEA GARDENS 



off a number of eggs which resemble a swollen 

 white bean. The egg attaches itself to any hard 

 substance in the mud, and if undisturbed becomes 

 a good, sizeable bath sponge in about three 

 years. 



In a farm the sponges are grown from small 

 pieces of living sponge attached to a cement 

 disk, which is then merely planted and the pieces 

 left to grow. 



Most sponges have several conspicuously large 

 holes at the top, while near the roots may be 

 noticed others which differ somewhat from the 

 usual ones. They are not so large as those at the 

 top, but larger than most of the others. These 

 are called the oscula, and are lined, when the 

 sponge is alive, with small tentacles which have a 

 convulsive movement. The oscula are in fact 

 mouths which suck the mud containing the plank- 

 ton into the body of the sponge, while the large 

 orifices at the top are really excretory organs 

 through which the sponge expels what it does not 

 use. Sponges therefore are a kind of automatic 

 filter which lives upon the germs that its fibrous 

 body is constructed to intercept. 



Sponge dealers differentiate between "roller" 

 sponges and others, classing them as a separate 

 variety or grade. The roller, however, is a mud 

 sponge which, for one cause or another, has 

 broken loose from its moorings. It then rolls 



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