THE SCYPHOMEDUSAE 



The Cubomedusae (Fig. 5) are medusiform onl}'. The 

 umbrella is square in section and rounded above ; a broad velarium, 

 containing endodermal canals and suspended by four perradial 

 fren'dae, or thickenings of the subumbrella, is present in many forms 

 (Cliarybdaea), but is sometimes absent (Procharagma) or slightly 

 developed (Procharybdis). The manubrium is four-square, its 



angles lying perradially. Four inter- 

 radial tentacles, long, hollow, and cylin- 

 drical, are always present ; they are 

 generally seated on lappets {pedalia), 

 which in some cases carry numerous 

 additional tenticles (Chirodropus). 



Fig. 5. 



Clwrifliilaca marsvpUilis (after Clans). 1. Tlie 

 fnur ainmlati'd tentacles are seen depcn<ling 

 lioiii the tour lappets ])laced at the fonr corners 

 of the qiiailraiiiinlar umbrella. These are inter- 

 ladiat. Two of the four perradial f^astric pouches, 

 n>])resentiii^: radial canals, are seen of a pale tint. 

 J-'ij, tra.slral tllaiijents (iiiterradial) ; 7i, the niodilied 

 perradial tentacles forming tentiiculocysts ; (!, cor- 

 ri'i- ricl^'e facing the observer and dividing adjacent 

 jioiiches of the umbrella; (IF, position of one of the 

 ^;iMital ban<ls. 2. View of the margin of the uni- 

 lirella of ClKtrybilaeu marsn/iinlix (natural size, after 

 Clans). At the four corners are seen the lappets 

 which support the long tentiicles, and in the middle 

 of each of the four sides is seen a tentacnlocyst ; 

 I'll, the vascular velarium, with its branched 

 1 . vessels. 



The nervous system is well developed, consisting of a sub- 

 unibrellar nerve ring, and of four larger perradial and four smaller 

 interradial rfanrilia, from which nerves pass to the sense organs, 

 muscles, and tentacles. The sense organs are tentaculociists, they 

 are always four in number and perradial in position, and lie in 

 sense pits on the exumbrella. In Charybdaea each consists of a 

 short stalk, the head of which carries a terminal otocyst with 

 numerous crystalline otoliths, two median and two pairs of lateral 

 ocelli. 



