10 Lessons in Zoology. 



Baby sponges can swim about in the water, but they 

 soon form a sucker at one end, by which they fix them- 

 selves (Fig. 3) to rocks, shells, or even the sea fans and 

 other branching corals, and after that they never leave 

 their home unless something tears them off. 



Many sponges grow on our New England coast, but 

 are too brittle to be of any use. A little white sponge 

 that grows among shells in the mud just below low-water 

 mark, consists of small branching tubes about an inch long. 

 It has no fibres in its skeleton, but everywhere in its flesh 

 are little three armed bits of lime called spicules (Fig. 4). 



The common finger-sponge (Fig. 5) grows in large masses 

 on rocks and piles. The dark red and soft yellow masses 

 found in salt water, and the white flattened cakes often 

 cast up on the shore and dried hard in the sun, are all 

 sponges, the last named called by the sailors " seamen's 

 biscuit." 



In a quantity of oyster shells there will usually be one 

 or two, at least, that have been attacked by the boring 

 sponge, which tunnels them through and through, and 

 fins' ;y "lestroys them by dissolving out all their lime. 



