FIG. 41. Obelia sp. A, portion of a colony, with certain parts shown in longi- 

 tudinal section; B, medusa; C, the same, with reversed umbrella; D, the same, 

 oral aspect; tid. i, 2, buds; bis, blastostyle ; COP, coenosarc ; ect, ectoderm: 

 end, endoderm ; ent, enteric cavity: gth, gonotheca (gonangium) : hth, hydro- 

 theca; /, lithocyst ; m.bd, medusa-bud: mnb, manubrium ; ntsgl, mesoglcea : 

 tnth, mouth: /, perisarc: P. i, 2, 3, 4, polypes: rad.c, radial canal; /, 

 tentacle ; vl, velum. 



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