TYPE CCELENTERA. 



101 



(Tessera) or Hue (Lucernaria) of adhesion. The depressions 

 of the subumbrellar surface, the funnels (/), are very deep in 

 Lucernaria, extending almost to the summit of the bell. 



2. Order Peromedusae. 



In this order the adult medusae are always free- swimming, 

 and are characterized by the bell being pointed in shape and 

 about its middle marked with a distinct constriction. The 

 coelenterou is obliterated at only four points, as in Tessera, 

 and they differ from the Staurornedusse 

 by possessing four sense-organs, the 

 four interradial tentacles of the primary 

 series of eight becoming modified to 

 form these structures, while the radial 

 ones retain their original character. 



3. Order Cubomedusse. 



This order, of which Charybdea (Fig. 

 53) is a typical example, is characterized 

 by the bell being of a cubical shape. 

 The interradial obliterations of the 

 coelenteron are linear, and, as in the pre- 

 ceding order, four of the primary ten- 

 tacles, these being the only ones which 

 develop, are modified to form sense- 

 organs. In this order, however, it is FIG. 53. Charybdea mar- 

 the four radial tentacles which form the supialis (after GLAUS). 

 sense-organs (so), the four interradial per- 

 sisting as tentacles (). 



4. Order Discomedusae. 



In this order, which includes the majority of the known 

 Scyphomedusse, all the eight primary tentacles are converted 

 into sense-organs, a number of secondary tentacles usually 

 developing at the margin (Fig. 54). The primary iuterradial 

 obliterations of the coelenteron do not develop, but on the 

 other hand secondary obliterations frequently make their 



