RHIZOSTOM^ — KHOriLEMA. 



705 



arm-disk pillars, and thus inrerradial in position. 4 separate genital cavities. 8 pairs (16) 

 simitar-shaped scapulets arise from the adradial sides of the arm-disk. Their upper sides 

 are conve.\ and bear frilled mouths and numerous, hollow filaments which are about two-thirds 

 as long as the scapulets themselves. The lower sides of the scapulets are concave and devoid 

 of mouth-openings or filaments. 



The 8 adradial mouth-arms are stout, triangular, and pyramidal, and exclusive of 1 heir 

 appendages they are about two-thirds as long as the diameter of the umbrella. The upper 

 parts ot these arms are coalesced with each other along half their lengths. These upper parts 



•'if ■ 



Fig. 423. — Rhopilema esculenta. After Kishinouye, in Zoolog. Jahrb., Abth. Syst., Bd. 12. 

 A and B, side and front views nf mouth-arms. C, sagittal section of medusa. D, oral view of arm-disk. 

 E, rhopalium. F, subumbrella showing canal-system (above) and muscular sectors (below). 



of the arms are free of mouths and are about as long as the scapulets, while the lower parts are 

 twice as long as the upper and bear numerous, frilled mouths and more than loo appendages. 

 There are 2 kinds of appendages — filamentous and fusiform. The fusiform appendages are 

 longer than the filaments and may be three-fourths as long as the diameter of the umbrella, 

 the 5 longest being found at the center and i at each perradial angle of the arm-disk. The 

 filaments are much more numerous than the fusiform appendages. There are no definite 

 terminal clubs at the lower ends of the mouth-arms. 



The central stomach gives rise to i6 radial-canals, 4 perradial, 4 interradial, and 8 

 adradial. These canals extend to the bell-margin and are connected one with another by 

 means of an indistinct ring-canal which is about midway between the margin and the periphery 



