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GENERAL BIOLOGY 



FIG. 65. A colonial Hydroid (Bougainmllea) and its Hydromedusa : 

 A, complete colony, natural size ; B, a portion of the same, magnified, 

 showing the branched stem bearing hydranths (hyd.} and medusae (med.), 

 one of the latter nearly mature, the others undeveloped : each hydranth 

 has a circlet of tentacles (t) surrounding the mouth (hyp.), and contains 

 an enteric cavity (ent. cav.) continuous with a narrow canal in the stem. 

 The stem is covered with a cuticle (cu.) ; C, a medusa after liberation 

 from the colony, showing the bell with tentacles (0 ; oc, eye-spots. 

 (From Parker, after Allman.) 



