CLASSIFICATION OF ACALEPHS. 457 



and in most cases this cavity has an opening or mouth ; 

 the edges of this opening are turned outwards and pro- 

 longed into fringes. And there are tubes which radi- 

 ate from the center of the body and unite with a tube 

 at the circumference. Jelly-fishes also have long or short 

 tentacles. 



The kinds of Jelly-fishes are numerous, and they vary 

 in size from those scarcely visible to those which are one 

 or two yards in diameter, and with tentacles thirty or forty 

 feet long. Alexander and Mrs. E. C. Agassiz (" Sea-side 

 Studies,") mention one which measured about seven feet 

 in diameter, and had tentacles more than a hundred feet 

 in length ! 



Jelly-fishes feed upon their own kind, and other marine 

 animals, which they secure by means of their tentacles 

 and lassos. On the tentacles of Jelly-fishes, and of 

 Polyps, there are numerous microscopic lasso-cells, each 

 containing a long spi rally-coiled thread or lasso, which 

 can be instantly darted forth and fastened upon the little 

 shrimp or other animal desired for food. 



According to Agassiz the Acalephse may be divided 

 into three Orders :* 



1. CxENOPHOR^ or acalephs with a more or less spherical or 



melon-shaped form, and with the body made up of eight 

 homologous segments bearing eight rows of locomotive ap- 

 pendages ; as Pleurobrachia, Beroe, Idyin, etc. 



2. DlSCOPHOR/E or jelly-fishes with a more or less hemispherical 



or disk-shaped form, with fringes or tentacles around the 

 outer margin ; as Aurelia, Cyanea, Pelftgin, etc. 



3. HYDROIDEA or acalephs which are plant-like, or polyp-like 



in form some kinds resembling ordinary medusae ; as Coryne, 

 or Sarsia, Tubul'arin, Hybocodon, Campanularia, Sertularia, 

 Tiaropsis, Physnlia, etc. 



* See the splendid works of Agasgiz : " Contributions to the Natural 

 History of the United States," from which all but one of our cuts of the 

 Acalephs are copied. 



