114 



ZOOLOGY FOR MEDICAL STUDENTS 



CHAP. 



polyps except that the mouth opening becomes divided up into a row 

 of separate openings. In such a case the individual thecae instead of 

 being circular are elongated (Fig. 52, D and E) and in extreme cases 

 they become very greatly drawn out and pursuing a tortuous course 

 give the mass of coral an appearance resembling that of the human 

 brain (" Brain Corals " — Fig. 52^ F). 



In the Mushrooin coral (Fungia — Fig. 53) a reproductive process 

 recalling that seen in the strobilization of the scyphistoma takes place, 

 the rim of the cup-shaped theca spreading out trumpet-fashion (Fig. 53, B) 



Fig. 52. 



Zoantharian Corals. A, Caryophyllia ; B, Lophohdia ; C, Solenistraea ; D, Dichocaenia ; 

 E, Favia ', F, Maeandra. 



and eventually forming a flat disc which with the upper part of the 

 polyp separates off and becomes independent, the process being repeated 

 over and over again. The adult Fungia, cut off in this fashion, lies 

 loose on the sea bottom, the theca being a flat disc with the septa 

 radiating outwards on its upper surface (Fig. 53, C). 



Many corals, including some of the commonest branching corals or 

 Madrepores, are what is termed perforate — the wall of the theca being 

 perforated by numerous openings which give it a spongy character. In 

 such a case the addition of calcium carbonate to the rim of the theca is 

 interrupted by tubular connexions between the main wall of the polyp 



