III. ANTEOZOA. 



257 



free particles between the inner ends of the selerosepta and tlie columella, 

 while synapticula: are small projections connecting the septa. As the 

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



Fig. 207. 



Fro. 208. 



Fig. 2V!.—Sclerophyllia mnrqarilicola. (After Khmzinger.) 



Fig. 208.— Section of coral of Caryophyllia t-i/aihu.i. (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 tabulae. Such tabulae occur in some Madreporaria, Octoeorallans, 

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



a 



FlO. 209. 



Fig. 210. 



Fig. 209. — Diaf^rammatic section of the flesh and coral of a hexacorallan ; above the 



line the section passes through the fe.sophagus, s," below the line it is lower down ; 



?•, directives ; coral black. 

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



lined, mesogkea black, entoderm dotted, coral white, a, theca; ^, mesenteries; 



c, costa^ ; f/, basal plate ; t', external wall ; /, selerosepta. 



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

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

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



