156 



ACTINOZOA. 



across the loculi like the bars of a grate." In 

 other cases, the dissepiments are replaced by the 

 development of successive horizontal floors, or 

 * tabulae ', which do not grow from the septa^, but 



Fig, 28. 



I 



Morphology of Zganthajiia sclerodeemata : — A diagram- 

 matic section of a living corallite. A, digestive cavity ; B, its com- 

 munication with the somatic cavity ; r, intermesenteric chamber ; 

 r', mesentery ; A, tentacle ; E, mouth ; Z, ectoderm ; H, endo- 

 derm ; 0, epitheca ; I, sclerobase ; K, theca ; A, septa ; M, palu- 

 lus ; N, columella ; O, dissepiments ; n, tabulae ; P, ccEnenchyma. 

 (The septa should be seen between the dissepiments, but are left 

 out for distinctness' sake.) 



extend, without interruption, across the entire 

 space bounded by the theca. On the outer 

 surface of the latter may occur 'costse', or vertical 

 lines, corresponding in position to the septa within; 

 ' exothecae ', which arise from the sides of the 



