25C 



C(ELENTERATA. 



The theca arises by a fusion of sclerosepta. If this fusion takes place 

 some distance inside the peripheral ends of the sclerosepta, the distal ends 



e: 



FIG. 206. Corallium rubrum, red coral. (After Lacaze Duthiers.) A, ciliated young; 

 .B, young colony ; C, part of colony with polyps in extension (a) and contrac- 

 tion (c); d, coenosarc; Z>, stereogram of a branch; 6, c, partly and completely re- 

 tracted polyps; rf, coenosarc; e, skeletal axis exposed; /', /, larger and smaller 

 coenosarcal canals; m, mesenterial filaments; s, oesophagus; <, retracted tentacles; 

 A, greatly, #, C, D, slightly enlarged. 



of these project on the outer surface as costae. Still outside these may be 

 a second cup, the epitheca. In the centre may occur a large calcareous 

 column or several smaller ones, the columella (fig. 208). Pali are small 



