10 M. F. Miiller on the Systematic Position of the Charybdeidse. 



traversed by deeper or shallower furrows, extending a greater or 

 less distance upon the dorsal surface ; the stomach has broad 

 lateral sacs, often in variable number, no radiating vessel or an- 

 nular canal ; the marginal vesicles are usually pedunculate ; the 

 tentacles, never exceeding the number of the stomachal sacs, are 

 always situated on the back, often springing very far from the 

 margin ; they are, moreover, characterized sometimes by a pecu- 

 liar rigidity, and sometimes by "a mobility not observed in 

 other Medusa)" (Eschscholtz*). The sexual materials of Cunina 

 are formed in the interior of the lateral sacs, and, indeed, in 

 their lateral angles, from which their place of formation extends 

 in the form of a horse-shoe from one sac to another. 



From all this, the alliance of Cunina, ^ginopsis, &c. with the 

 Hydroida is equally loose and forced, and as little effected by 

 any transitions as that of the Charyhdeida with the Acalephsc. 

 If, therefore, the separation of these two families from their pre- 

 sent alliances is not subject to any serious doubt, neither does 

 any such appear to present itself against their union. It is true 

 that a wide gap exists between Cunina and Tamoya, but not 

 wider than between the Medusoid of Corymorpha, without ten- 

 tacles, eyes, or mouth, and Olindias, or between Nausithoe and 

 Cephea — a gap like that between the young brood and the ma- 

 ture animal, over which fancy readily finds a gradual passage by 

 intermediate steps, and not a wall of separation set up by incom- 

 patible characters. From the shallow furrows in the flat, slightly 

 notched disks, often (according to Gegenbaur) of a cartilaginous 

 hardness, of many Cunina, the intermediate form of jEgina 

 citrea leads to Charybdea mnrsupialis, and to the complex bells 

 of the Tamoyce, whilst, even in both the extreme genera, the 

 combination of a velum with a disk not entire at the margins, 

 observed neither in Hydroida nor in Acalephse, occurs as a com- 

 mon character. From the flatly stretched stomachal membrane 



the boundary between body and velum. As in the ^ginidee the muscular 

 membrane of the lower surface is continued over a notched margin, the 

 marginal membrane may, in like manner, be wanting in disks with entire 

 margins, even in Hydroid Medusae ; at least, I am unable to detect any 

 trace of it in a small Campanularia-huA, Tintinnabulum resupinatum, n. s., 

 which always swims with the disk reversed. 



* This is the case in jEgina sulfureay as it is called in Eschsch. System 

 p. 9, or ^g. citrea, at p. 113. The second Eschscholtzian species, JEgina 

 rosea, is probably to be separated from this, and referred to Cunina, as, 

 according to Eschscholtz's figure (tab. x. fig. 3 a), it appears more natural 

 to ascribe to the stomach six lateral sacs excavated opposite to the origin 

 of the tentacles, than twelve such organs. If, with Gegenbaur, we charac- 

 terize the ^ginidce by " rigid tentacles," the choice of the name after that 

 of a species distinguished from all other Medusae by the exact opposite 

 cannot be described as particularly happy. 



