F. S. CONANT ON THE CUBOMEDUSJE. 29 



These mutual relations of stomach, stomach pockets and lamella? 

 will perhaps be made clearer if a comparison is drawn between them 

 and the similar structures of a Hydromedusa. Liriope, one of the 

 TrachomedusEe, is a good form to take for such a comparison, since by 

 reason of its direct development from the egg it is free from the compli- 

 cations of hydroid medusa?. The young medusa has at first a simple, 

 undivided gastro-vascular cavity which later is divided up into the 

 central stomach and the typical radial to circular canals of the Hydrome- 

 dusae by means of fusions between the two endodermal surfaces. Dia- 

 grams a, b and c of Fig. 35 represent very schematically this process of 

 division into stomach and canals. In a we have a projection upon a 

 plane surface of the primary, undivided gastro-vascular cavity, as seen 

 from above ; 6 shows the first four points of fusion in the interradii ; 

 c represents those four points expanded by growth in all directions into 

 broad cathammal plates in such a way as to leave the stomach in the 

 centre, the radial canals in the perradii, and the circular canal in the 

 periphery as all that remains open of the primary simple cavity. These 

 broad plates of vascular lamella, separating the narrow radial canals, 

 persist in the adult Liriope to tell the tale of the formation of the defini- 

 tive gastro-vascular system. It seems to me that we are justified by 

 analogy in drawing a similar conclusion for the Cubomedusa?. In d of 

 Fig. 35 is represented a projection of a Cubomedusa, in which the 

 homology of the stomach pockets with the radial canals of the Hydro- 

 medusa, and of the narrow strips of fusion with the broad cathammal 

 plates, is shown at a glance. To make the comparison more perfect we 

 have only to remember that in the Cubomedusa there exists below each 

 interradial vascular lamella a connecting canal (Figs. 16, 29 and 35 d, cc] 

 uniting the two separate adjacent pockets. This, as has been pointed 

 out by other writers, is the representative of the circular canal of the 

 Hydromedusa?. Practically the only difference between the structure of 

 the gastro-vascular system of the Cubomedusa? and that of a form such 

 as Liriope, is that in the latter the fused areas have broadened out at the 

 expense of the radial canals, while in the Cubomedusa? 011 the contrary 

 they have become long and narrow. 



One is strongly tempted by the foregoing comparison to speculate a 

 little as to whether the reproductive organs of the Cubomedusa?, which 

 lie in the stomach pockets and are generally supposed to be endodermal, 

 may not bear some closer relation to those of the Trachomedusa j , which 

 lie "in the course of" the radial canals (Lang's Text-book) and by common 



