148 DISCOPHOR^. Part III. 



shape, but without the slightest indication of prolongations at the four corners of 

 the aperture. In somewhat older specimens the corners of the mouth were drawn 

 out into four open lobes, as in Aurelia (PL XI". Fig. 17), so that the closing of 

 the arms, and the soldering of their margins, must be the result of a later progress 

 in their growth. 



When describing the mode of development of Pelagia cyanella, page 128, I 

 ought to have stated that, long previous to those observations, Krohn had already 

 given a much fuller account of the direct transformation of the embryo of the 

 Pelagia noctiluca of the Mediterranean into a genuine Medusa, without strobila 

 stage, than I have been able to trace in our species. See Miiller's Archiv, 1855, 

 p. 491. According to Kolliker and Gegenbaur, Zeitschrift fur wiss. Zoologie, 1853, 

 p. 328, the development of Cotylorhiza (Cassiopea borbonica) follows, probably, the 

 norm of Aurelia. 



