III. ANTHOZOA. 



257 



free particles between the inner ends of the sclerosepta and the columella, 

 while synapticulce are small projections connecting the septa. As the 

 polyps grow they build the theca3 higher and higher and consequently draw 



Fio. 208. 



FIG. 207. Sclerophyllia mnrgariticola. (After Klunzinger.) 



FIG. 208. Section of coral of Caryophyllia cyathus. (After Koch.) Outside the theca, 

 septa (I-XII) of first and second order, their pali and, in centre, columella. 



out from the deeper portions, which may become cut off by horizontal parti- 

 tions, the tabulee. Such tabulae occur in some Madreporaria, Octocorallans, 

 and Millepores (p. 241) which were formerly united in a group Tabulatae. 



FIG. 209. 



Fio. 210. 



FIG. 209. Diagrammatic section of the flesh and coral of a hexacorallan ; above the 



line the section passes through the oesophagus, s; below the line it is lower down ; 



7-, directives : coral black. 

 FIG. 210. Diagram of the relations of the coral to the polyp. (After Koch.) Ectoderm 



lined, mesogloea black, entoderm dotted, coral white, a, theca; b, mesenteries; 



c, costae ; d, basal plate ; e, external wall ; /, sclerosepta. 



It was once thought that the coral was a calcined portion of the soft 

 parts and hence that sclerosepta were hardened sarcosepta etc. This has 

 been disproved. The sclerosepta are formed in the radial chambers between 



