PHYLUM CCELENTERATA 133 



Order 3. Cubomedusae. SCYPHOZOA with four perradial 

 tentaculocysts; tentacles interradial; umbrella four-sided, on> 



FIG. 82. SCYPHOZOA. A, Tessera princeps, order STAUROMEDUS.E. B, Peri- 

 phylla hyacinthina, order PEROMEDUS^E. C, Charybdea marsupialis, order CUBO- 

 MEDUS^E. G, gonads; Gf, gastral filaments; Ov, gonads; Rf, annular groove; 

 Rk, marginal bodies; Rm, circular muscle; T, tentacles. (From Sedgwick, 

 after Haeckel.) 



shaped; no alternation of generations. Example: Charybdea 

 (Fig. 82, C). 



Order 4. Discomedusae. SCYPHOZOA with four or more 

 _ perradial and four or more interradial tentaculocysts; umbrella 

 .disc-shaped; alternation of generations. Examples: Aurelia 

 (Fig. 79), Pelagia, Cassiopea. 



4. CLASS III. ANTHOZOA (ACTINOZOA) 



There are no medusae among the ANTHOZOA. The polyps 

 may be distinguished from those of the HYDROZOA by the pres- 

 ence of a well-developed stomodaeum or gullet, which is fastened 

 to the body-wall by a number of radially arranged membranes 

 called mesenteries. Many of the polyps are solitary, but the 

 majority produce colonies by budding. Most of the ANTHOZOA 



