OCEANIA LAXGUIDA. 71 



iiTOtrularly all over the siirfiiee ; the walls of the tentacles are thin, 

 leaving a wide tulK' running to their extremity ; the labial iblds of the 

 short digestive cavity are simple, the edges not being fringed (/, Fig. 

 95) ; the bell is perfectly transparent and ex- 

 ceedingly thin, remaining of the same thick- 

 ness close to the edge ; the veil is of medium 

 size. The ovaries and the base of the diges- 

 tive cavity are light brown ; the base of the 

 tentacles is somewhat darker. The number of 

 tentacles is from thirty-two to forty ; the Me- 

 dusa measures from three fourths to seven ^ 

 eighths of an inch in size. The marginal cap- 

 sules are formed by division, a small jiortion 

 of the capsule being separated by a constriction, and a granule devel- 

 oped in it (o, Fig. 94) forms the new capsule, which gradually becomes 

 more and more distinct m older specimens. 



The observations of Wright on Laomedea acuminata, combined with 

 the development given here of a Medusa (Fig. 96) similar to the one 

 he observed, give us the complete history of the genus Oceania. It is 

 particularly important on account of the light it throws on the probable 

 identity of many of the species described by Forbes under the name of 

 Thaumantias, and which are distinguished by the greater or smaller 

 number of tentacles, and the position and size of the ovaries. Difi'er- 

 ences, similar to those hj which he has distinguished such a large 

 number of species, are readily traced in the diflerent stages of our 

 Oceania. Professor Agassiz had separated the Hydroid figured by 

 Wright, as a distinct genus, from Clytia, on account of the peculiar 

 position of the marginal capsules, totally different from what is observed 

 in that genus. The development of the Medusa shows this to be a 

 correct appreciation of the differences noticed in the young ; but as the 

 genus of the adult Medusa is one already well known, Wrightia, the 

 name given to the Hydrarium by Professor Agassiz, must be rejected. 

 We have on our coast two species of Wrightia?, one of which produces 

 planula?, and resembles, in its general aj^pearance and mode of branch- 

 ing, the Laomedea acuminnta figured by Wright in the Edinburgh New 

 Philosophical Journal for 18-50 ; the latter, however, produces Meduste, 

 while the second species is closely allied to the European Campamdaria 

 syrinrja ; it has reproductive calycles similar to the calycles of the 

 Campamdaria fastirjiata Alder ; it differs considerably from the figure 

 of the C fii/ringa given by Van Beneden, the stolon of our species 

 being as strongly ringed as the pedicel ; the calycle is likewise slightly 

 constricted in the middle. This species has not been found with 



Fig. 95. Magnified view of Uio actliiostome. 7', chymiferous tiiU' : _/", one of the foui' ^ini])le 

 lobes of the aetinostonie. 



