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. 
Fig 204.— Diplorict cerebriformte , or “Brain-coral;” one half natural size. Bermudas. 
