PHYLUM CCELENTERATA 



109 



of the umbrella is fringed by numerous close-set marginal 

 tentacles (t). 



In the centre of the lower or sub-umbrella surface is a 

 four-sided aperture, the mouth (mtk), borne at the end of 



gen 



e.p.p 



l.T.C 



^r—p.rc 



Fig. 51 — Aurelia aurita. Ventral view — two of the oral arms are removed; a.r.c, 

 radial canal; gon, gonads; i.r.c, radial canal; mg. l/>, marginal lappet; mtk, 

 mouth; or. a, oral arm; p.r.c, radial canal; s.g.p, sub-genital pit; t, 

 tentacles. 



an extremely short and inconspicuous manubrium : sur- 

 rounding it are four long delicate processes, the oral arms 



