246 CCELENTERATES : ACALEPHS. 



somewhat like a melon with one end cut off. The 

 mouth occupies the whole of the cut-off end, and the 

 stomach occupies a large part of the interior of the 

 animal. In summer it sometimes appears in such 

 swarms as to tinge large patches of the sea with a 

 delicate rosy hue. It is very voracious, and feeds 

 mainly on other jellyfishes, sometimes capturing those 

 nearly as large as itself. 



True Medusae, or Discophora. 



These have the body in the form of a hemispheric 

 disk, more or less flattened. Of these disk-shaped Me- 

 dusa none are more beautiful in their appearance or 

 interesting in their histoiy than the Aurelia, or Sun- 

 fish, represented in Figure 477. This Jellyfish is 

 common on the coast of New England, is about a 

 foot across in the larger specimens, and lives but a 

 single year. In the spring it is about a quarter of an 

 inch in diameter, and on pleasant days moves in large 

 swarms near the surface of the water. About the 

 middle of summer they become full grown. Towards 

 the close of summer they lay their eggs, and in the 

 autumn they perish. At length the eggs hatch, and 

 the \ht\c planiilcs, as the newly hatched Jellyfishes are 

 called, swim about in the water by means of tiny 

 appendages which naturalists call cilia. Soon each 

 becomes attached to a rock, shell, or seaweed, and is 

 then called scyphostoiita, F'igure 475. Then the body 

 begins to divide by horizontal constrictions, and soon 

 appears as in Figures 474 and 476, and is then called 

 strobila. At length the segments become more and 

 more separated, and the uppermost one drops oft, then 

 the next one, then the next, and so on till each in turn 



