SCYPHOMEDUS^E MAHSUPIALIDA. 



259 



modified. As in Lucemaridcie, the vascular spaces arc wide pouches 

 divided from each other by four narrow septa (figs. 1!S } 199). 



The nervous system is allied to that of the Hydromedusce by the 

 presence of a sharply denned nerve-ring. This nerve-ring is placed 

 on the .sub-umbrella side of the bell, and, since at the bases of the 

 four sense organs it lies further from the margin than it does at the 

 corners of the bell, it has a sharply marked, zig-zag course. The 

 nerve fibrillfe given off from it mostly supply the muscular system of 

 the sub-umbrella, and there give rise to numerous reticula of nbrilla? 

 connected w r ith large ganglion cells. Large bundles of fibrilhe com- 

 p;i ruble to nerves have only been found in the four radii of the mar- 

 ginal bodies. The latter attain a high degree of development, since 

 the knob-like swelling in which they terminate possesses, in addition 

 to the lithocyst, a complicated visual apparatus consisting of two 

 large unpaired median eyes and four 

 small paired lateral eyes. 



The generative organs have a. very 

 peculiar form. They are separated 

 from the gastric filaments and as 

 thin, rather broad plates attached in 

 pairs to the four partition walls, 



length of the 

 Unfortunately 

 known of the 



mar- 



FIG. 199. The apicalhalf of a Charybdea 

 divided transversely, seen from the 

 sub-umbrella side. The four oral 

 arms are visible. Oc, Ovaries on the 

 four septa, S ; Ost, ostia of the gas- 

 tric pouches ; Gf, gastric filaments. 



reach the whole 

 vascular pouches, 

 nothing is as yet 

 development. 



Fam. Charybdeidae. Cli<injlnl<'<t 

 xMjt'niTix Per. Les. (Murxiipiulix Plum-i 

 Les.) Mediterranean. 



(3) Sub-order : Discophora (Acra- 

 speda) , Ephyra-medusce. 



Disc-shaped Accuepha, the margin of ivhose disc is divided into eight 



lobes. They have at least eight sub-marginal sense organs contained in 



niches, and with the same number of ocular lobes. As a rule there are 



four great cavities in the umbrella for the generative organs. 



The Discophora, which are generally known simply as 

 can at once be distinguished from the Calycozoa and the 

 by the disc-shaped lobed umbrella and usually by the large size of 

 the oral tentacles. The lobes of the umbrella, however much they 

 may differ in detail, can always be reduced to the eight pairs of 

 lobes of the Ephyra, which, as the common starting-point of the 

 Discophora, presents most clearly the eight-rayed symmetry char- 



