ANATOMY OF OBELIA 



271 



of the oar- weed (Laminaria). A portion of a colony is shown 

 in fig. 57, A. The colony consists of a root-like branching 



Fig. 57- 



A, part of a colony of Obelia geniculata magnified ; /*/, hydrotheca contain- 

 ing a hydranth ; gt, a gonotheca enclosing a blastostyle with medusa buds ; 

 /, perisarc ; /, terminal growing point. B, a sexually mature female 

 medusa, seen from below ; m, mouth ; re, radial canal ; cc, circular or 

 ring canal ; go, gonads. C, diagramniatfc longitudinal section through a 

 medusa ; ///, mouth ; inb, manubrium : gv , gastro-vasculur cavity ; re, 

 radial canal; cc, ring canal; el, endoderm lamella; oc, ocellus; ot, ptocyst. 

 The section is supposed to pass through a radial canal on the left side and 

 an adradial tentacle on the right. Endoderm black ; mesoglcea shaded ; 

 ectoderm represented by a broken line. D, the bases of two tentacles 

 magnified, showing oc, ocelli ; ot, an otocyst on an adradial tentacle ; cc, 

 ring canal. r- 



stem, the hydrorhiza, which adheres to the oar-weed and 

 sends off at frequent intervals little branches some 10 to 



