THE SCYPHOMEDUSAE 



The Cubomedusae (Fig. 5) are medusiform only. The 

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

 containing endodermal canals and suspended by four perradial 

 frenulae, or thickenings of the subumbrella, is present in many forms 

 (Charybdaea), 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 tentacles (Chirodropus). 



FIG. 5. 



CJianjMaca inarsupialis (after Glaus). 1. The 

 four annulated tentacles are seen depending 

 from the four lappets placed at the four corners 

 of the quadrangular umbrella. These are inter- 

 radial. Two of the four perradial gastric pouches, 

 representing radial canals, are seen of a pale tint. 

 Fg, gastral filaments (interradial) ; R, the modified 

 perradial tentacles forming tentaculocysts ; G, cor- 

 ner ridge facing the observer and dividing adjacent 

 pouches of the umbrella; GF, position of On* of the 

 genital bands. 2. View of the margin of the um- 

 brella of Charybdaea marsupial!* (natural size, after 

 Clans). At the four corners are seen the lappets 

 which support the long tentacles, and in the middle 

 of each of the four sides is seen a tentaculocyst ; 

 Vd, the vascular velarium, with its branched 

 1 . vessels. 



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

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

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

 muscles, and tentacles. The sense organs are tentaculocysts, 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. 



