Kill/us Ki\I i: mTYI.oUHIZA. (5(51 



Besides these short appendages, less numerous but somewhat larger ones terminate in a 

 flattened hall-like to disk-like end set in a socket. At the point of bifurcation of each of the 

 8 mam mouth-arms is a filament which is circular in cross-section and nearly half as l<m as 

 the mouth-arm itself. Tins filament tapers gradually from base to tip, but usually terminates 

 in a swollen end. Centripetal to these 8 main filaments are 3 to 5 other, somewhat shorter 

 filaments arising between the frilled mouths of each mouth-arm. Near and at the center of the 

 arm-disk there are numerous slender filaments, about one-third as long as the main filament, 

 which terminate in expanded disk-like conical ends. 



A unitary, cruciform, suhgenital space opens outwardly at the 4 suhgenital ostia. Thus 

 it is possible to pass a probe into any one of the subgenital ostia and out through tin oni- 

 on the opposite side of the arm-disk without penetrating any tissues of the medusa; the 

 subgenital space being actually outer world (C, fig. 410). The complexly folded, ucmtal 

 membrane is developed upon the sides and upper floor of this subgenital space, and thus 

 upon the lower floor of the central stomach. 



The central stomach is large, occupying the spacious cavity of the central dome of the 

 exumhrella ( B, fig. 401). 1 1 to 13 radial-canals per octant (88 to 124 in all) arise from the 

 margin of this central stomach and extend outward to the bell-margin. There is no dis- 

 tinct ring-canal, but instead there are numerous, lateral anastomoses between the radiating 

 canals, forming a complex network of vessels under the floor of the subiimbrella. The main 

 canals of the 8 mouth-arms empty by S adradial openings into the central s'oinach. I'.ach 

 of these mouth-arm canals bifurcates, and the two main branches give rise to numerous, 

 lateral diverticula which lead to the gutters of the frilled mouths. 



I here is a well-developed unitary, marginal ring of circular muscles and an inner zone 

 of radial-muscles in the subumbrella. Bethe, 1905, has shown that \\hen the medusa pulsates 

 these inner-lying radial-muscles contract ht-fui;- the ring-muscles, though the latter lie nearer 

 to the sense-organs, from which the contraction-impulse arises. This more rapid response 

 of the radial-muscles is due to the fact that their latent interval between the reception of the 

 stimulus and their response is less than in the case of the circular muscles. Bethe also finds 

 that the normal pulsation consists of 80 to IOO contractions at fairly regular intervals with 

 periods of total rest between them. These are then followed by a pause which lasts as long 

 as 3 to 20 of the normal pulsations. For further details of the character of the pulsation, tin- 

 reader should refer to Rhizostoma /n/lnin. 



The bell of this medusa is rich oli\e, tending to orange, 01 to hrowiiish-vellow. being 

 especially dark and brownish on dome-like apex of the exumhrella. The rich yellow color 

 is found on both exumbrella and subumbrella, and is due to the presence of numerous M ll<>\\ 

 to brown plant cells (Zoochlorellte) which float in the canal-system and infest the enioderm 

 of the medusa. Claus, 1885, finds these cells in the 8 lobed eplnia when onlv 1.5 to i mm. 

 wide. 



The arm-disk and mouth-arms are usually pale milky-white tinged with delicate creamy- 

 yellow. The free outer edges of the mouths are tinged with purple vai\in;to blue in \iolet. 

 The terminal portions of the appendages, which arise between the frilled mouths, are deep 

 blue tending to purple, or violet. 



This medusa is found in the Mediterranean, bur is quite capricious in its appeal a nee. 

 being at times very rare. According to CJraeHe it is not seen everv year in the Adriatic .it 

 I ncste, but adult medusae are usually seen from July to September, while small ones are found 

 in July and August. At Naples adult medusa- are commoner from August to ( (ctoberthan in 

 winter, when they become \er\ rare, being only occasionally found in mid-winici. Keller is 

 of the opinion that this medusa is a deep-water species which only occasionally comes to the 

 surface when sexually mature, ami that tin- \OIIIIL; lemam near the bottom of the sea. Yan- 

 hoften, 1888, records the capture of a young individual of this medusa at \ssab in the Red 

 Sea on June 10, 1885. The medusa must have been introduced into the Red Sea through tin- 

 Sue/ (.'anal. It has also been found in the Atlantic, near the Canary Islands. (See C. ;//'/<- 

 /.;. iiilii I laeckel.) 



The development of this medusa has been studied by Busch, Frant/.ms. ( ic^cnb.iu i . 

 Kowalevsky, Claus, (ioette, du 1'lessis, Mem, and ntheis, and has furnished some of the 

 e\ i deuce for a conf roveiM between Claus and ( ioette concerning the development of the ;;ast n>- 

 vascular cavity of the sc\ phostoma. 



