CALYPTOBLASTEA 



155 



coenosarcis completely invested by the cuticular secretion, the perisarc^ 

 composed of chitin and produced to form cups round the hydranths 

 (hydrothecae) and the blastostyles (gonothecae). The hydranth of Obelia 



Fig. 114. Part of a branch of Obelia sp. To the left a portion is shown in 

 section. After Parker and Haswell. ect. ectoderm; end. endoderm; mth. 

 mouth; coe. coelenteron; esc. coenosarc; psc. perisarc; hth. hydrotheca; 

 bis. blastostyle ; med. medusa-bud ; gth. gonotheca. 



is an expansion of the coenosarc, ending in a prominent oral cone, sur- 

 rounded by a single ring of rather numerous tentacles, which have a 

 solid core of endoderm cells. The blastostyle has a mouth but no 



