CHAPTEE XII 



COELENTERATA {CONTINUED) : SCYPHOZOA = SCYPHOMEDUSAE 



CLASS II. SCYPHOZOA = SCYPHOMEDUSAE 



The Scyphozoa are jelly-fishes, usually found floating at or near 

 the surface of the sea. A few forms (Stauromedusae) are attached 

 to rocks and weeds by a stalked prolongation of the aboral region 

 of the umbrella. With this exception, however, they are all, in 

 the adult stage, of the Medusa type of structure, having a bell- 

 shaped or discoid umbrella, from the under surface of which 

 depends a manubrium bearing the mouth or (in Ehizostomata) 

 the numerous mouths. 



Although many of the species do not exceed an inch or a few 

 inches in diameter, others attain a very great size, and it is among 

 the Scyphozoa that we find the largest individual zooids of the 

 Coelenterata. Some Discophora have a disc three or four feet in 

 diameter, and one specimen obtained by the Antarctic Expedition 

 of 1898-1900 weighed 90 lbs.'- The common jelly-fish, ^wre^a, 

 of our coasts belongs to a species that appears to be very variable 

 in general characters as well as in size. Specimens obtained by 

 the " Siboga " in the Malay Archipelago ranged from 6 to 64 cm. 

 in diameter. The colour is very variable, shades of green, blue, 

 brown, and purple being conspicuous in many species ; but a pale 

 milky-blue tint is perhaps the most prevalent, the tissues being 

 generally less transparent than they are in the Medusae of the 

 Hydrozoa. The colour of the Cubomedusae is usually yellow or 

 brown, but CharyMea xaymacana is colourless and transparent. 

 The deep-sea species, particularly the Periphyllidae, have usually 

 an opaque brown or dark red colour. The surface -swimming 



' C. E. Borchgrevink, "First on the Antarctic Continent," 1901, p. 227. 



310 



