86 



E. PERCIVAL 



are least unanimous on tlie subject of the origin of the manu- 

 brium of the non-terminal ephyra. ' According to Goette it 

 proceeds from a completely new formation after the casting 

 off of the preceding ephyra ' (Heric). Glaus (1) figures Aurelia 

 as having, between two ephyra rudiments, a circular shelf 

 or horizontal fold of the two-layered wall of the connecting 

 tube. The ectodermal portion of the fold is apparently con- 

 tinuous all round, but the endodermal portion is interrupted in 



Text-fig. 1. 



Interradias Perradius 



S.O.- 



Early stage in strobilization. 



each interradius. Its four radial components appear from within 

 as grooves, the adjacent ends of which grow towards each other 

 and meet between the longitudinal muscle-strand and the 

 ectoderm, thus forming the continuous ring-canal which Claus 

 calls the ' ring-sinus of the proboscis (i. e. manubrial) disc '. 

 As a result of this the septal or longitudinal muscle-strand in 

 the region connecting adjacent ephyrae is surrounded by 

 endoderm, and when the edge of the incipient manubrium 

 becomes split off from the exumbrella of the preceding ephyra, 

 it bends outwards, leaving the septal muscles to act as con- 

 necting strands between the two ephyrae. In fact the original 



