254 COMPARATIVE ZOOLOGY. 



FIG. 203. Astrceapallida; natural size. Fejee Islands. 



A coral-reef is formed by many Corals growing togeth- 

 er. It is to the single Coral-stock as a forest is to a tree. 



Fio. 204. Diplaria eerebriformw, or " Brain-coral ;" one half natural size. Bermudas. 



