250 



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 





Fig. 206. — CoraXlium ruhruvi, vqH q(^v,\\, (After Lacazo Diitliiers.) -^, ciliated young; 

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

 tion {(■); d, co3nosarc; D^ stereogram of a brancli; h, c, partly and completely re- 

 tracted polyps; r/, ccenosarc; c, skeletal axis exposed: /', /, larger and smaller 

 ccenosarcal canals; m, mesenterial filaments; *■, (.esophagus; t, retracted tentacles; 

 A^ greatly, B, C\ I\ slightly enlarged. 



of these project on the outer surface as cos(a\ Still outside these may be 

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

 column or several smaller ones, the aihi)iu//<i (lig. 20S). Pali are small 



