CORAL POLYPS. 



81 



times growing to a diameter of three feet. The common 

 large West Indian brain-coral is Mceandrina labyrinth ica. 



In Astrcea 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-Thouipsou. 



of Astrangia Dana? 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. 



