ioo PARASITES INFESTING MEDUSA. PART m. 



sand-hoppers, and a galsemon of glassy transparency, 

 move about in the substance of their disc and arms, 

 entering unscathed by the poisonous darts which inflict 

 instant death on others of their class. The Libanea 

 crab, of gigantic size compared with its host, is in the 

 habit of taking up its abode between the four columns 

 of the Rhizostoma. But the most singular intruder is 

 the Philomedusa Vogtii, which is a polype with twelve 

 thick short tentacles, its whole body and tentacles being 

 covered with cilia and thread-cells. These polypes live 

 in the disk, arms, and stomach of the medusae, and, when 

 taken out, their stomachs are found to contain frag- 

 ments of the tentacles of their host, and even the thread- 

 cells with their stings. The larger polypes devour the 

 smaller ones, and the latter live for weeks within the 

 larger ones without apparent inconvenience to either. 6 



Mr. M'Cready mentions that the larvae of the medusa 

 Cunina octonaria swim as parasites in the cavity of the 

 bell of the medusa Turritopsis nutricula, which not only 

 furnishes a shelter and dwelling-place to the larvae 

 during their development, but it also serves as a nurse, 

 by permitting the parasites, which adhere by their ten- 

 tacles, to take the food out of its mouth by means of 

 their long proboscides. They undergo many trans- 

 formations, and become nearly perfect medusae while 

 within their nurse. 



Medusae of different species are met with in every sea 

 from the equator to the poles. They are eminently social, 

 migrating in enormous shoals to great distances. The 

 largest shoal of young sea nettles on record was met 

 with in the Gulf Stream, off the coast of Florida, by a 

 vessel bound for England. The captain likened them 

 to acorns ; they were so crowded as completely to cover 

 the sea, giving it the appearance from a distance of a 



* Dr. F. Miiller, of Santa Caterina. 



