MAEGELIS CAROLINENSIS. 



157 



the bell is almost spherical ; the thickness of the rlisk is so great that 

 the cavity of the bell only extends to half the height of the vertical 

 axis. (See Fig. 241.) 



In young specimens (one tenth of an inch in height) just liberated 

 from the Hydroniedusarium, the outline of the disk is bell-shaped (Fig. 

 244), the cavity of the bell is large in proportion, and the thickness of 

 the upper part of the bell is not one third of the height of the actinal 

 axis. The digestive cavity and the peduncle are one ; it is bottle- 

 shaped, cylindrical, and not yet divided by four longitudinal furrows 

 into genital pouches. These small Medusae have, like the young of 

 Bougainvillia, when freed from the Hydroniedusarium, but two tenta- 

 cles at the base of each of the chymiferous tubes (Figs. 244, 245), the 



Fig. 215. 



Fig. 2«. 



digestive cavity terminates likewise with perfectly simple, stiff oral ten- 

 tacles, which begin to branch only in somewhat more advanced stages. 

 The generic identity of BougainvilUa hritannica with our Margelis 

 carolmensis is perhaps not better shown than by the agreement of the 

 young Medusa) in all their essential features, while the Hydrarium shows 

 that the specific difference between the English and American represen- 

 tatives is not to be questioned. See the observations of Dalyell on the 

 development of his Tuhular'ui ramosa, PI. XI. Vol. I., Animals of Scot> 

 land, and the figures of Hodge of Podocoryne Alderi, which I presume 

 is only a young of one of the species of Bougainvillia (Margelis Steenst.) 

 of Forbes. It seems therefore perfectly justifiable to reconstruct the 

 genus Bougainvillia in such a way as to separate from it those species 

 which have a long, slender digestive cavity, with but slightly branching 

 tentacles, under the name of Margelis. 



The oral tentacles are, in the youngest Medusaa (Fig. 244), small. 



Fig. 244. Young Margelis, having only two marginal ttntack's at the base of each chymiferous 

 tube, and simple oral tentacles. 



Fig. 245. Young Margelis, seen from tlie abactinal pole, in the condition of Fig. 244. 



