BEEOID MEDUSA, OB CTENOPHOEiE. 229 



are one or two yards in diameter, and with tentacles 

 thirty or forty feet long ; and Mrs. Agassiz, in her 

 beautiful book, "Seaside Studies," mentions one which 

 measured about seven feet in diameter, and had ten- 

 tacles more than a hundred feet in length ! 



Jelly-Fishes are a hungry race, and feed upon their 

 own kind, and other marine animals, which they se- 

 cure by means of their tentacles and lassos. On the 

 tentacles of Jelly-Fishes, and of Polyps too, there are 

 numerous lasso-cells, — too small to be seen without 

 the microscope, — each containing a long, spirally-coiled 

 thread or lasso, ~which can be instantly darted forth 

 and fastened upon the little shrimp or other animal 

 which is desired for food. 



BEROID MEDUSiE, OR CTENOFHORiE. 



Tlie Beroid Medusas are more or less spherical, or 

 egg-shaped, with eight rows of locomotive fringes divid- 

 ing the surface of the body as the ribs divide the surface 

 of a melon. Pleurobrachia is one of the most common 

 kinds on the northeast coast of the United States, and 

 in its movements and curious appendages is one of the 

 most wonderful of all the Medusse. It is transparent, 

 and besides the eight rows of fringes mentioned above, 

 it. has two most extraordinary tentacles, one on either 

 side of the body ; and no form of expansion or con- 

 traction, or curve or spiral, can be conceived of which 

 these tentacles may not assume. 



Bolina and Idyia are other ctenophorse common on 

 the northeast coast of the United States. The Rose- 

 colored Idyia is three or four inches long, and shaped 

 somewhat like a melon with one end cut off. The 

 mouth occupies the whole of the cul^off end, and the 



