( i n;< i\ U K IM.IIII'liVr.LA. 



545 



as the basal, central, and buccal stomach. The central stomach is a 4-sided prism, the sides 

 being interradial and the angles perradial in position. The lowi-r <u huccal part of the stomach 

 hangs freely in the cavity of the bell, being joined to the subumbrellu at 4 perradially situated 

 points at its inner end. There are 4 longitudinal, interradial, thickened regions in the wall 

 of the buccal stomach, which extend downward to the mouth-opening. The central stoni.n h 

 is a wide cavity which communicates hv 4 perradial openings with the gastrovascular space 

 of the subumbrella of the medusa. These 4 openings are narrow, elongate, longitudinal 

 clefts, and their edges are lined with numerous gastric cirri which project into the space of 



Ptriphylla hyacintliina. 



FIG. 342. After Vanhbffen, in Valdivia Expedition. 



FIG. 343. After Vanhoffen, in Nordisches Plankton. 



Showing variation in shape of bell. 



the stomach. The basal stomach is a 4-sided pyramid and 8 rows of gastric cirri extend 

 up the 4 sides near the angles to the apex of the pyramid where they meet. These rows of 

 cirri are continuous with those surrounding the 4 perradial side-openings of the central stomach. 

 The gastrovascular coronal sinus of the subumbrella is thus connected with that of the stomach 

 by the 4 perradially situated ostia of the central stomach. These open into this wide annular 

 cavity which occupies the mid-region of the subumbrella above the zone of circular muscles. 

 Below these, however, it appears as a broad, simple, annular space, which extends outward 



