TOILERS IN THE SEA. 109 



CHAPTER IV. 

 SPONGE WEAVERS. 



WHAT is a sponge? is a question much more 

 readily asked than answered. Not so many 

 years ago a speedy answer would, have been given, 

 even if not satisfactory. In those days there was 

 a rough-and-ready classification of animals, plants, 

 and minerals in vogue, subject to three primitive 

 definitions, animals possessing life and motion, 

 plants life without motion, and minerals without life 

 or motion. Between this triumvirate was the world 

 divided, until it became manifest that there were 

 undoubted animals which were as fixed as plants, 

 and undeniable vegetables which were as free in 

 their movements as animals. The old formulae were 

 no longer to be relied upon, and new definitions 

 attempted, but with these we will not trouble, since 

 all definitions are but temporary, and but relatively 

 satisfactory. Even now there are some persons who 

 require some persuasion before they will accept the 

 free swimming diatoms as real vegetables, or the 



