140 



MARINE INVERTEBRATES 



Pelagia cyanella. 



C.frondosa. This species 

 has a circular disk, on the 

 margin of which are sixteen 

 sense-organs (tentaculocysts), 

 but no tentacles. The lower 

 end of the manubrium, which 

 in other jellyfishes is an open 

 mouth, is closed by eight arms 

 which emanate from it and are 

 usually extended laterally, ly- 

 ing parallel to the disk. These 

 arms are much branched, and 

 the branches, in turn, have 

 numerous appendages. Some 

 of these appendages look like 

 little polyps and have mouths 

 surrounded by crowns of ten- 

 tacles ; others are ovoid bodies 

 without external openings, but 

 with a central cavity connected 

 with vessels leading to the 

 arms. The former are mouths, 

 but the function of the ovoid 

 bodies is not known. Although 

 able to swim freely, Cassiopeia 

 lies usually on its back, as if 

 attached, and languidly opens 

 and closes its disk, rarely 

 changing its position. Its arms, 

 extending upward, appear like 

 the fronds of algae. These 

 jellyfishes are common on the 

 Florida coast, huddled together 

 on the sands of the coral reefs. 

 (Plate XLIV.) 



