F. S. CONANT ON THE CUBOMEDUS^E. 19 



space, which divide the primitively simple space into the four stomach 

 pockets, have come to an end, leaving a connecting canal (cc) in each 

 corner as all that remains of the primitive uninterrupted communica- 

 tion between all parts of the peripheral system. It is from these four 

 connecting canals that the tentacle canals take their origin. From this 

 point of origin each tentacle canal passes downwards, surrounded by the 

 gelatine of the pedalium, into the tentacle proper. 



The connecting canals are of morphological importance in that they 

 are supposed, with much reason, to represent in the Cubomedusa? the 

 circular canal of the Hydromedusae. 



9. Reproductive Organs. The sexes are separate in Charybdea. In 

 both sexes the reproductive organs consist of four pairs of long leaf -like 

 bodies, each leaf attached along one edge to the wall of the subumbrella 

 in an interradius (see Fig. 1, r), and hanging free in the stomach pockets. 

 From this position in the stomach pockets it is evident that the repro- 

 ductive organs are endodermal. The lines of attachment of each pair is 

 just internal to the longitudinal vascular lamella that fuses the outer 

 and inner walls of the stomach pockets together in the interradius (ivl), 

 and the reproductive organs are therefore structures belonging to the 

 subumbrella. It is interesting to note how careful examination of the 

 medusan organization takes away from the importance of the outer cup, 

 the exumbrella, and adds to that of the inner, the subumbrella. We 

 have seen that the phacelli and the sensory clubs, from whose position it 

 would be supposed that they belonged to the exumbrella, are organs of 

 the subumbrella, and that there is no muscle-tissue in the exumbrella ; 

 we find now that the reproductive organs belong to the subumbrella, 

 and it will be shown later that the tentacles, like the sensory clubs, are 

 structures of the subumbrella also. To the exumbrella are left only the 

 functions of support and covering. 



The mature reproductive organs extend very nearly throughout the 

 entire vertical length of the bell, and are therefore found in the series of 

 cross-sections in all but the uppermost and lowermost (Figs. 7-15 r). 

 The organs consist of germ cells within, covered by an epithelium of 

 columnar cells that shows here and there nettle cells. The ova are found 

 with different amounts of yolk, according to age, surrounding a large 

 nucleus almost devoid of chromatin and an intensely staining nucleolus. 

 In young ova there appears very plainly in every case at least one small 

 deeply staining body inside the nucleus, which very much resembles the 

 nucleolus. These are probably so-called yolk nuclei, and while I have not 



