THE DISCOPHORA. 223 



radiating series of thickenings of the oral wall of each cham- 

 ber. 1 



All the other Discophora, which are what are commonly 

 known as " Jelly-fish," are free, and some attain a very large 

 size. In the adult (Fig. 18) the umbrella is thick and divided 

 by small marginal notches into as many (usually eight) lobes. 

 At the bottom of each notch, often protected by special lob- 

 ules, is an oval lithocyst, supported by a cylindrical pedun- 

 cle, the cavity of which is in direct communication with 

 one of the radiating canals of the umbrella (Fig. 28, IV.). 

 This canal communicates with the exterior on the aboral side 

 of the base of the peduncle. 2 The thick mesoderm of which 

 the great mass of the umbrella consists is composed of a ge- 

 latinous connective tissue, in the meshes of which is a watery 

 fluid, containing numerous nucleated cells which exhibit amoe- 

 boid movements. On the oral face there is a broad zone of 

 striped muscle, made up of fusiform fibres placed side by 

 side. In Aurelia aurita, the angles of the four-sided hy- 

 dranth are produced into long foliaceous lips, the margins 

 of which are beset with minute solid tentacula (Fig. 18). 

 The gastric cavity contained in the hydranths terminates, be- 

 neath the centre of the umbrella, in a somatic cavity which 

 passes into four radially-disposed, wide offshoots, or genital 

 sinuses, the oral walls of which constitute the roof of the gen- 

 ital chambers (Fig. 18, II.). From their margins the narrow 

 branching radial canals are given off. The peripheral ends 

 of these unite when they reach the margin. 



Each genital chamber is a recess, surrounded bv a thick 

 wall of the oral face of the umbrella, in the centre "of which 

 only a small aperture is left (Fig. 18, I., G). The roof of 



I T7i tj 1S the fl °° r of the £ enital sirms ; ^ is much plaited 

 and folded, and the genital elements are developed in it. Its 

 inner or endodermal wall is beset with small tentacular fila- 



n J ^Jtt^ ° f Lu f r J} aria wi th the Discophora were shown in my lect- 

 S.5S h- Ti 'T noL aa . zeU ^. 1856 - Keferstein, " Untersuchungen iiber 



U s v?ew a d'prof ttTk 'I ^ TT^, 011 the * enu8 ' ™ly "confirms 

 tins view, and Prof. H. J. Clark arrived independently at the same conclusion : 

 Lucernaria the Ccenotype of the AcalepTm" ("Proceedings of the Boston 

 Society of Natural History," 1862}. The Lucernaria (Carduella, Alln an) 

 cyathiformis of Sars differs mucn from the ordinary Lucernarioe, especially in 

 the position of the genital organs as longitudinal thickenings in the wall's of 



Tf?; ! t " < ;- Cavity ; f A^ 1Iman ' " 92 th - e Structure of Carduella cyathiformis » 

 ( 1 ransaction 3 of the Microscopical Society," viii) 



anertnJ^ nlrSf cana ? f of ) he nectocalyx communicates with the exterior by 

 apertuies on the summits of papillose elevations in some medusoids 



