SPONGES 105 



in these clear waters. The sponges are dragged up by hooks a 

 primitive method which restricts the fishing to shallow water, the 

 fishing here being in water not deeper than thirty feet, but usually 

 three to twenty feet. The sponges are " killed " by being exposed 

 on the beach for several days; they are then placed in " crawls," 

 or pens, where they are washed by the action of the waves for 

 about a week ; then, if clean, they are dried, assorted, strung on 

 cords, pressed and baled for shipment. The sponge-fisheries are 

 of considerable value, and much attention is being given to the 

 subject of artificial propagation. It is thought that such beds 

 could be subjected to the regulations which govern oyster-beds. 

 Already the planting of sponges has been shown to be practi- 

 cable. The living sponge is cut to pieces, and the cuttings are 

 placed in favorable localities. Pieces planted in Florida waters 

 attain a marketable size in one year. 



Sponges reproduce by eggs formed in the mesoderm. The 

 eggs escape as ciliated spheres and swim about until they find a 

 place on which to attach themselves. As soon as they become 

 fixed they grow with much rapidity into mature individuals. 



Some species seem to prefer association with other animals and 

 live as commensals with crabs. The crab Dromia is always con- 

 cealed under a sponge, which grows upon its back. Spider-crabs 

 are often overgrown with sponges as well as seaweeds. In this 

 case, however, the crab finds and plants the sponge himself. 

 Aplysella violacea overgrows worm-tubes. Many sponges afford 

 shelter to numerous small animals which bore into their bodies 

 for protection, no animal seeming to feed upon the sponge. 



Sponges may be found in tide-pools, on the under side of 

 stones, on seaweeds, and so on. A small bright-red incrusting 

 sponge with irregular lobe-like branches is common on the New 

 England coast ; a thin yellow incrusting sponge also is found on 

 the under side of stones. Grantia ciliata, a small urn-shaped 

 species, having a large aperture at the summit, is found in tide- 

 pools. 



Perhaps the most singular in habit of any sponge is Cliona 

 sitlpliHrca, the boring-sponge, a common species found from Cape 

 Cod to South Carolina and abundant in Long Island Sound. It 



