SEA ANEMONES AND CORALS 41 



form and color. They vary in size from that of a pin's head to 

 several feet across, and they live at all depths and in a great variety 

 of situations. 



A. coral polyp is only a sea anemone which deposits a plate of 

 lime salts at the base of its barrel-like body and between the 



Fig. i6; Star-Coral Showiug Liviug Polyps. From a Specimen in the Xew York Aquarium. 



radial partitions of the stomach cavity. These lime salts form 

 a stony "skeleton" or substance which we commonly call "coral." 



It is well to remember that the coral animals are not "insects" 

 but are merely sea anemones which form stony 'skeletons." 



Although sea anemones and coral polyps resemble beautiful 

 flowers when fully expanded, they quickly contract into a mere 

 dome-shaped mass when disturbed. In this way the coral polyps 

 are protected by withdrawing into their stony cup-shaped bases. 



