STRUCTURE AND HABITS 

 OF THE LIVING CORAL 



THE BEAUTIFUL white stony ornaments 

 which are sold in curio shops bear little re- 

 semblance to the living green, gold or orange 

 corals. In fact they are merely the bleached 

 skeletons of their former selves. The crea- 

 ture which forms the skeleton is an animal very low in 

 the scale of evolution and is very similar in general 

 structure to a sea anemone. 



A sea anemone grows attached to rocks and consists 

 essentially of a soft tubular body with an opening at 

 one end, which is its mouth, surrounded by a ring of 

 hollow tentacles. Within the opening of the mouth the 

 skin projects inwards to form a passage or throat known 

 as the stomcxloeum. 



The coral in its simplest form is the skeleton of a 

 simple anemone-like creature known as a polyp. The 

 skin covering the lower part of the polyp has the pe- 

 culiar capacity of forming on its surface a stony layer, 

 much as the skin of an oyster forms a shell outside it 

 and enclosing it. Since the polyp is tubular the stony 

 layer takes the shape of a limestone cup. A short pillar- 

 like fold of skin in the center of the base forms a verti- 

 cal axial rod called the columella. 



The coral polyp is complicated by vertical folds of 

 the wall of the tube. There are two types of folds. One 

 of these consists of an infolding of the entire body wall. 

 The folds project radially part way into the interior of 

 the cylindrical polyp. The skin turned inside by the 



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