90 THE OCEANIC HYDROZOA. 



Fam. RHIZOPHYSIDyE. 

 Genus RHIZOPHYSA {Pemi and Lesueur). 



Hydrosonia filiform ; neither nectocalyces nor hydrophyllia. Tentaciila branched, the 

 branches peculiarly modified at their extremities, but without true sacculi. 



Rhizophysa filiformis ? PI. VIII, fig. 1-3. 



Physsoplioru fiUfornns, Forskal, 1775. 

 Ejnbulia filiformis, EscLscliolz, 1829. 

 Rhizophysa filiformis, Gegenbaur, 1853. 



The pneumatophore is pjTiform, and, like the rest of the body, of a pale, pinkish hue, 

 but with a very deep red patch surrounding the aperture of tlie pneumatocyst.^ 



The coenosarc, long and cylindrical, is hardly at all twisted upon itself, and gives 

 attachment at intervals to slender polypites, about half an inch long. 



The endoderm of these organs exhibits short villi, containing clear spaces. A tentacle 

 arises at the junction of the polypite with its pedicle, and the stem of this organ when 

 contracted is not more than an inch long, thick at its base, thin at its extremity, and 

 usually coiled upon itself. It is capable of great extension (to as much as two or three 

 inches in length), and then appears like a slender thread. Floating at the top of the water 

 in a glass vessel two or three inches deep, the animal could fix itself by means of the 

 lowermost bi'anches of its tentacles to the bottom, and holding on by them, raise and lower 

 itself at will. 



The stem of the tentacle gives off a series of lateral branches in which no distinction 

 into pedicle, sacculus, and filament is discernible. These branches arise from only one side 

 of the stem, and those which are nearest the attached end are mere small, oval buds, while 

 the distal ones are delicate threads as much as half an inch in length. Each thread is 

 a double-walled, csecal tube, with one wall thicker than the other in the proximal portion, 

 and alone containing the thread-cells, which are scattered over the whole surface in the lower 

 part of the organ. The thread-cells are spheroidal, and measure about 5^gth of an inch 

 in diameter. 



The polypites appear to be attached indifferently to cither side of the coenosarc (?), and 

 at the base of the pneumatophore several small and partially developed ones could he 

 observed. There was no indication of any nectocalyces. 



' WLose structTire is particularly described above. 



