F. S. CONANT ON THE CUBOMEDUS.E. 15 



Fig. 9, sp) and separated from one another in the interradii merely by 

 four thin vertical strips of vascular lamella (ivl) or fusion between the two 

 endodermal surfaces of a primitively single undivided peripheral cavity. 

 The structure is exactly that which we should have if in a Hydromedusa, 

 for example Liriope (Trachomedusse), the four radial canals broadened 

 out and the intervening cathammal plates correspondingly narrowed, 

 until the relations in size were just reversed, and instead of four narrow 

 radial canals separated from one another by four broad cathammal 

 plates, we had four broad radial canals or pouches separated by four 

 narrow cathammal plates. 



The stomach pockets communicate at their top with the central 

 stomach by means of four moderately large openings, the gastric ostia. ' 

 These are seen in a side view of the whole animal as triangular spaces 

 (Fig. 1, g. o.) near the top of the broad perradial sides. In Figures 7 and 

 8 they are seen in cross-sections, in Fig. 4 in vertical section. 



The communication between the stomach and each stomach pocket 

 is guarded by a valve that can cut the one entirely off from the other. 

 The valve is simply the flexible lower margin of the gastric ostium, a thin 

 vertical fold of the floor of the stomach, semilunar in shape, just at the 

 point where it is passing over into the stomach pocket. A longitudinal 

 section, such as is shown in Fig. 4, gives the best idea of the form and 

 position of the valve that can be obtained from any simple section. 

 Internal to the valve is seen a depression of the stomach wall, almost 

 worthy to be called a pocket. The valve itself lies as a wall across the 

 end of this depression, obstructing a free course to the stomach pocket. 

 It will be seen at once that any pressure of fluids in the stomach against 

 this vertical wall, or valve, would serve only to press it against the inner 

 surface of the exumbrella, and thus effectually close the entrance into 

 the stomach pocket. Such a closure would both keep the juices of the 

 stomach from entering the pockets and the embryos in the pockets from 

 entering the stomach before the proper time. 



The depression of the floor of the stomach just internal to the valve 

 may possibly be a structure of some morphological significance. In one 

 series of sections it was found that in two of the quadrants the depression 

 was deeper than that represented in Fig. 4, and extended perceptibly into 

 the outer or vertical portion of the suspensorium. Fig. 32 is a diagram 

 giving a vertical reconstruction in the perradius of the cross-sections in 

 which this deepened depression was noticed. Fig. 31 is a drawing (the 

 outline by camera lucida) of one of the cross-sections, through the lower- 



