116 



EMBRYOLOGY 



stages the marginal pouches become narrower and move 

 apai't; the sixteen regions of fusion [cathammata] thus 

 spi'ead out into a bilaminar phite, which connects all of the 

 marginal pouches with one another : the mednsoid, vascular, 

 or catJiamvial plate. 



The detachment of the Ephjra now takes place, and from 

 this time on it moves about fi'eely by rhythmical contractions 

 of its discoid body, the former point of attachment being 

 directed upwards, and the manubrium downwards (Fig. 51, 

 ii). The columellae, which are frequently the means of the 

 final connection with the nurse form, now deofenerate. It 



Fib. 57. — Interradial longitudina section through an Ephyra monodisca, with 

 the Scyphistoma tentacles still retained (diagram modified from Goette). pb, 

 proboscis; tr, septal funnel; gf, gastral filament ; so, septal ostium ; vf, constrict- 

 ing annular groove. 



is probable that the last metamorphosed remnant of the 

 septal infundibula can be recognized in the four sub-genital 

 cavities (p. 122) lying on the sub-umbrellar side below the 

 gonads of the medusa. With the degeneration of the 

 columellae the boundary between the central stomach and the 

 peripheral intestine entirely disappears, and the boundary 

 at which the ectoderm of the oesophagus is continuous with 

 the entodermal lining of the peripheral intestine is indicated 

 only by means of four tentaculoid gastral filaments (Figs. 

 57, 58 gf), which have budded forth at the bases [oral ends] 

 of the coluraellse. 



