CIV 



THE VOYAGE OF H.M.S. CHALLENGER. 



connecting proximal arch has become lost (Navphanta, PI. XXVII., XXVIII. ; Atolla, 

 PI. XXIX.). Whilst the first and oldest order of the Discomedusaj, the Cannostomse, 

 still present more or less the original genital conditions of the Tesseronise, these have 

 disappeared entirely in the other Discomedusae, in all Semostomse and Ehizostomse. As 

 here the four primary cathammal nodes are resorbed, and both the four perradial pouches, 

 separated by them and the coronal sinus are consequently merged in the flat central 



Fig. Q. Zoncphyra 2>clagica (Discomedusa, Epliyrkla). 



Subumbral view, giving the four orders of transverse axes (with twice as many radii). Tlio oral cross 

 (as) and the four perradial sense clubs (o') lie in the four perradii (Order I.). The gastral filaments 

 (/), the genitalia (s), and the four interradial sense clubs (o-) lie in the four interradii (Order II.). 

 The eight tentacles (to) and the tentacular coronal pouches (bt) lie in the eight adradii (Order III.). 

 The sixteen marginal lobes (?) lit' in the sixteen subradii (Order IV.). Sixteen bifurcate coronal 

 pouches, eight tentacular (bt) and eight rhopalar (bo) radiate from the central stomach (</). 



stomach, four simple interradial genitalia usually lie in the subumbral wall of the central 

 stomach, lying nearer its centre in proportion as the Ephyronise character is more highly 

 developed and the peripheric umbrella corona becomes extended at the cost of the central 

 umbrella disk. The delicate, thin gastrogenital membrane (gg) on whose endodermal 

 inner surface the four genitalia are situated, is certainly simply termed the bottom of the 

 stomach or subumbral wall of the central stomach ; but it must always be borne in mind 



