KHIZOPODA. 



23 



and sucking in the surrounding water through innu- 

 merable pores upon their surface, which conveyed 

 through every part of their soft texture materials for 

 their subsistence, we could scarcely expect the asser- 

 tion to be credited, at least, without considerable 

 hesitation ; and yet no fact in natural history is more 

 easily demonstrated. Not only do the fragments 

 of flints examined under the microscope reveal the 

 fossilized texture of the sponge, but not unfrequently 

 the shells of the animalcules upon which they lived 

 are found in their substance, and even portions of 

 the sponge itself, as yet unpetrified, are often con- 

 tained in their interior. 



FlG. 11. HAI.ICHONDIUA OCULATA.* 



/\s, hals, the sea ; 



s, chondros, cartilage. 



