50 



STRUCTURE OF THE SPONGE. 



structure of the sponge, with which we are all 

 familiar, is the framework, or under skeleton of the 

 living animal ; the characters presented by it 

 greatly differing in the various species, which are 

 extremely numerous. 



In the common sponge, the fibres are elastic and 

 horny in their texture, and when highly magnified, 

 appear to be tubular. In other species, the frame- 

 work consists of a firm inflexible tissue, of inter- 



SPONGES. 



The upper figure represents one with horny fibres ; the under figure, one 

 with silicious spicula. 



crossing filaments, also tubular, and the living 

 gelatine exhibits bands of a more cartilaginous con- 

 sistency than ordinary, and is also more or less 



