II. SCTPHOZOA. 



245 



bells) being attached to the under side of the float. Physalia, the Portu- 

 guese man-of-war, occurs as far north as New England. It is brightly 

 colored, and, sitting high on the water, is driven about by the wind. It 

 stings very severely. 



Sub Order IV. DISCONANTH^E. Float a flattened disc with con- 

 centric air chambers; the manubrium projects from the centre of the lower 



FIG. 189. American siphon ophores. A, Nanomia earn. (After A. Agassiz.) B. Velella 

 meridionalis. (After Fewkes.) C, Diphyes praya. (After Fewkes.) 



surface of the float. Porpita* with circular disc. Velella* (fig. 189), the 

 paper sailor, has a triangular ' sail ' on the disc. Both are tropical and 

 subtropical. 



Class II. Scyphozoa (Scyphomedusae). 



The Scyphozoa parallel the Hydrozoa in that they frequently 

 have an alternation of generations. The asexual generation is the 



FIG. 190. FIG. 191. 



FIG. 190.-Scyphostoma of Aurelia aurita. (From Korschelt-Heider.) fc, perisarc cup ; 

 pb proboscis; s, stalk; t, gastral folds; tr. ectodermal funnels. 



Mo. 191. bection of Scyphostoma. (From Hatschek.) gr, gastric pouches; s, gas- 

 tric folds ; SOT, muscles. 



scyphopolyp or scyphostoma, the sexual an acraspedote medusa. 

 In contrast to the Hydrozoa the asexual stage plays a subordinate 



