ANATOMY OF OBELI A 



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 t part of a colony of Obclia geniculata. magnified ; ///, hydrotheca contain- 

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

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

 medusa, seen from below ; in, mouth ; re, radial canal ; cc, circular cr 

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

 medusa; tit, mouth; ittl>, manubrium : gv, gastro-vascular cavity; re, 

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

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

 an adradial tentacle on the right. Kndoderm black ; mesogloea 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. 



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

 sends off at frequent intervals little branches some 10 to 



