§25. 



BRAIN-STONE CORAL. 625 



like that of the Fungia, is adherent to the rock, with which, 

 being formed of a like material, it becomes identical. As 



Lign. 138.— Brain-stoke Coral. 

 {Meandrina cerebri formis.) 



one fleshy mass expires, another appears, and gradually 

 expands, pouring out its calcareous secretion on the parent 

 mass of coral ; thus successive generations go on accumu- 

 lating vast beds of stony matter, and laying the foundations 

 of coral reefs and islands. We may compare, observes 

 Mr. Lyell,* the operation of the zoophytes in the ocean, to 

 the effects produced on a smaller scale on land, by the 

 plants which generate peat ; in which the upper part of the 

 Sphagnum, or peat-moss, vegetates, while the lower is en- 

 tering into a mineral mass, in which the traces of organiza- 

 tion remain when life has entirely ceased. In these Corals, 

 in like manner, the more durable materials of the generation 

 that has passed away, serve as the foundation over which 



* Principles of Geology. 



