66 



THE SCYPHOMEDUSAE 



The tube of the manubrium leads into a short gastric cavity; 

 from this four broad shallow perradial canals or pouches, separated 

 by narrow interradial mesenteries, lead to the circular canal at the 

 edge of the bell. This canal is further subdivided by fusion of its 

 exumbral and subumbral walls into pouches, eight (Charybdaea) 

 or sixteen (Chirodropus) in number ; from these lead the canals 

 of the tentacles and velarium. The mesenteries are traversed 

 by an endoderm lamella, and carry interradial phacellae at their 



FIG. on. 



1. Horizontal section through the umbrella and 

 manubrium of Charybdaea niarsupialis (modified 

 from Glaus) ; Ma, manubrium ; SB, side ridge (per- 

 radial) ; CR, corner ridges, separated by CG, the 

 interradial corner groove ; Ge, the genital lamellae 

 in section, projecting from the interradial angles on 

 eacli side into UE, the radial canals of the umbrella ; 

 SU, the subumbral space. 2. Vertical sections of 

 Charybdaea marsupialis, to the left in the plane of an 

 interradius, to the right in the plane of a perradius ; 

 Ma, manubrium ; EAx, gastric cavity ; Gh, gastral fila- 

 ments (phacellae) ; CG, corner groove ; SR, side ridge ; 

 EnL, endoderm lamella (line of concrescence of the 

 walls of the enteric cavity of the umbrella, whereby its 

 single chamber is broken up into four pouches) ; Ge, 

 line of attachment of a genital band ; EU, circular 

 canal, giving origin to TCa, the tentacular canal ; Ve, 

 velarium ; F r, frenum of the velum ; Tc, tentaculocyst. 

 (From Lankester.) 



2. 



aboral ends. In a few cases eight adradial arms carrying 

 digitate filaments grow out from the exumbral body wall, 

 and hang free in the radial canals (Chirodropus). As in Hali- 

 clystus, the generative organs grow out from the sides of the in- 

 terradial mesenteries, and form leaf-shaped projections into the 

 radial canals. 



Practically nothing is known of the development of this 

 group. 



