CASSTOPEA XAMACIIANA. 225 



liiive totally disappeared. Tlie lines ol' ndliesion separating the radial canals are faintly 

 visible as radiating lines of greater transparency. 



The fonr lips of the month are spread ont into a cross-shaped fignre, and one 

 may look directly through the Inmen of the oesophagus into the stoniaeii and see the 

 fonr gastric filaments (Figs. 29 and ."()). Each one of the four lips is nearly scpiare, and 

 from its two outer angles thei'e are two grooves that extend oltliquely inward until they 

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



there is a, groove that is continuous witli ll ther two gi'ooves, and that extends into 



the stomach. On the interradial side of each of the eight labial grooves, there mav be 

 sei'u 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 jirocesses, tlie digitella, which are arranged in a single continuous 

 series. 



Fig. (3o is a, section of an e])liyrnhi 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 vanisli. 



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

 treated very briefly. Wiiile the umbrella I'cmains 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 jire soon drawn out into extended lobes 

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

 continued outward ;dong each of these lobes as a midrib. We have then eiglit 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 ]>arts 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 Cotylorliiza. 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 iinniels, oi- oscida. and a small vesicle developed at 

 the tip of each oral arm. The othei- p(ntions of the arm are still open and fringed with 

 digitella, as before, but the outline is no longer a regular ein\e, for there are folds iji the 



