442 EVENINGS AT THE MICKOSCOPE. 



the surrounding water enters on all sides. Tliese pres- 

 ently unite into slender pipes, whicli, irregularly mean- 

 dering, are continually uniting into larger and yet larger 

 canals ; of which the greater open spaces that you see 

 are the oblique divisions. These have certain outlets, 

 called oscula, on the surface, from which the stream is 

 poured oat that has thus made the grand tour of the 



SECTION OF SPONGE. 



whole interior. Such osGitla, as you perceive on the 

 remainder of the Salichondria, are usiially raised on 

 slight eminences ; and resemble, especially when in 

 living action, miniature volcanoes, vomiting torrents of 

 water and granules of effete matter, instead of fire and 

 aslies. 



During life these grannies were much more diffused, 

 and formed a considerable portion of the living flesh, 

 the remainder being composed of a glairy sarcode, al- 

 most fluid. The whole was maintained in position by 

 the solid spicula of flint, which you see abundantly'- in 



