254 



COMPARATIVE ZOOLOGY. 



Fig. 203. — Astrcea pallida ; natural elze. Fejee Islande. 



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

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



Fio. iOi.—Diploria ceretri/ormis, or " Bi'nin-ci>ral ;" one half iiatnrnl size. Bermndas. 



