CASSIOl'KA XA.MACIIANA. 225 



have totally disappeared. Th<' lines of adhesion separating the radial canals arc faintly 

 visible as radiating lines of greater transparency. 



The four lips of the mouth are spread out into a cross-shaped figure, and one 

 may look directly through the lumen of the oesophagus into the stomach and see the 

 four gastric filaments (Figs. 29 and 30). Each one of the four lips is nearly square, and 

 from its two outer angles there are two grooves that extend obliquely inward until they 

 meet and form a V. The point of the V is in an angle of the oesophagus, along which 

 there is a groove that is continuous with the other two grooves, and that extends into 

 the stomach. On the interradia.1 side of each of the eight labial grooves, there may be 

 seen a small roughly circular area that is less transparent than the rest. These areas are 

 the nettle batteries, first seen in the strobila. The margins of the lips are provided 

 with numerous small processes, the digitella, which are arranged in a single continuous 

 series. 



Fig. Go is a section of an ephvrula that has just become free. In this stage there is 

 still an opening through the aboral wall of the stomach, and one may see the last vestige 

 of the connection between the columella and the exumbrella, which contains also the 

 degenerating remnants of the septal muscle. 



At a little later stage, when the opening in the roof of the stomach has closed, 

 both the septal muscles and the septal funnels totally disappear. Sometimes one, some- 

 times the other, is the first to vanish. 



The Later Stages. The later stages in the development of Cassiopea will be 

 treated very briefly. While the umbrella remains at first unchanged, the metamor- 

 phosis of the month parts is inaugurated by the growth of the two outer angles of each 

 of the more or less quadrate lips, so that they are soon drawn out into extended lobes 

 (Fig. 31). At the same time the pillars of the proboscis thicken, and the mesogloea is 

 continued outward along each of these lobes as a midrib. We have then eight oral 

 arms, each with a longitudinal groove, supported by a midrib, and fringed with digi- 

 tella, arms very similar to those characteristic of the genus Aurosa Haeckel ('79). But 

 it is only the mouth parts of Cassiopea that may be said to pass .through an Aurosa stage, 

 for the comparison cannot, at this time at least, be carried to the other organs. 



Clans has described ('83) some of the principal stages in the metamorphosis of Pilema 

 (Rhizostoma) and Cotylorhiza. He regards the formation of the eight oral arms as a dif- 

 ferent process in these forms from what occurs in Aurosa. But it appears to be merely the 

 same thing expressed differently. 



In the next stage we find two oral funnels, or oscula, and a small vesicle developed at 

 the tip of each oral arm. The other portions of the arm are still open and fringed with 

 digitella, as before, but the outline is no longer a regular curve, for there are folds in the 



