482 EVOLUTION OF ANIMALS Part V 



Adhesive disks holding to surface 



Fig. 23.12. Upper, adult Gonionemus murbachi, a beautiful jellyfish with a disk 

 hardly an inch in diameter and 60 to 80 tentacles that bear rings of stinging cells. It 

 goes through a medusa and a polyp stage, the latter so minute it is little known. 

 Very abundant in the quiet inlets of Cape Cod. Lower, a young jellyfish resting on 

 the bottom and holding fast with its suction disks. {Lower, after Perkins, Proceeds. 

 Academy of Natural Sciences, Philadelphia, 1902.) 



The Portuguese man-of-war (Physalia pelagica) floats on the surface of 

 warm seas in many parts of the world and was named Portuguese only because 

 seamen saw it floating near Portugal (Fig. 23.13). It occurs in the Gulf Stream 

 from Florida northward, occasionally drifting into harbors in New England. 

 Its gas-filled float, about ten inches long, is translucent blue and rose-tinted, 

 colors that are continued in the polyps which trail backward for 1 to 40 feet. 

 Their beauty is strictly for the eye, nothing to be fondled. Colonies and pieces 

 of tentacles that have been picked up half dead upon the beach have caused 

 serious poisoning. The long defense polyps paralyze a good-sized fish and, due 

 to their extraordinary contractions, are able to present the fish which they have 

 snared at the mouths of the short feeding polyps. 



The "little sail" (VeleUa) is a similar hydrozoan colony supported by a 

 float about two inches wide that bears an erect projection, the "little sail." 

 These are common drifters often whole fleets of them, in the warmer waters 

 of the west coast. 



Class Scyphozoa 



The Scyphozoans include the larger jellyfishes. Their radial symmetry is 

 based upon four or a multiple of four structures, such as the eight notches in 

 the margin of the umbrella (Fig. 23.14). The polyp stage is either lacking or 

 the polyps are minute, A full-grown polyp suggests a stack of diminutive 



