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 (mt/i), borne at the end of 



gen 



-pr.c 



IIP 



Mil |1UU U 



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; vtg. //, marginal lappet; mih, 

 mouth; or. a, oral arm; f.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 



