CORAL POLYPS. 81 
times growing to a diameter of three feet. The common 
large West Indian brain-coral is Meandrina labyrinthica. 
In Astrea pallida Dana, of the Feejee Islands, the polyps 
are pale, the disks bluish gray, and the tentacles whitish. 
The polyps of many corals are beautifully colored. Those 
Fig. 53.—Lophohelia prolifera.—After Wyville-Thompson. 
of Astrangia Dane Agassiz are white. In this coral, as 
observed by Dana, the polyps stand prominently above the 
calicles, as only their bases secrete coral. The tentacles 
have minute warty prominences, each full of lasso-cells. 
