A BUSY SKELETON. I/ 



have been removed from it. They are a jelly-like sub- 

 stance which lines all the holes and pores of the skel- 

 eton. Over the outside of the sponge is a thin, net-like 

 membrane, which opens and closes the canals that run 

 their crooked course from the middle of the .sponge to 

 its surface. 



Opening and closing its' many holes, to let in and 

 throw out food, is about all the work the living sponge 

 does. The floating food is admitted into a large num- 

 ber of tubes or canals, and is carried through a thou- 

 sand or more cavities which take up the food and di- 

 gest it. After the nourishment of the food has been 

 received, the useless matter is carried out through the 

 porous canals, and expelled at the surface of the 

 sponge. 



On the water-bottoms sponges show all sorts of 

 forms. Some seem to be made of glass threads. Some 

 are flat like sheets. Others are like clumps or small 

 bushes ; still others resemble vases. 



When they are brought to the surface by the men 

 and boys who fish for them, the sponges are thrown 

 into tanks of water, after which decay soon begins. 

 Then they are taken out and all the soft, or what was 

 living matter, is beaten out of them. After this the 

 skeletons are dried, and are ready for market. When 

 they reach the first market-center they are further 

 cleaned, are cut into regular shapes, and are sometimes 

 bleached by the use of chemicals. The sponge trade 

 at the principal European market amounts to nearly a 

 million dollars annually. 



Such is a short, natural history of a busy skeleton, 



or of a bucket full of holes that never leaks. 

 L. c.- 2 . 



