them into the mouth. Little sense organs may occur 

 in four notches in the scalloped margin, or in eight 

 notches, or in some higher multiple of four. Tentacles 

 may also occur in marginal notches, alternating with 

 the sense organs, or in other positions as well. Some- 

 times they form a fringe of indefinite number. 



The jelly of scyphozoan medusas can be very 

 bulky, and it contains many cells and strengthening 

 fibers. Sometimes it is almost of a cartilaginous tex- 

 ture, so firm that one can jump on such an animal 

 without crushing it. Even the firmest ones, however, 

 are at least 94 per cent water. 



The jellyfish is always the predominant stage in 

 the scyphozoan life history. The polyp stage either is 

 very small or is missing altogether. When present, it 

 may transform directly into the adult; or it may elon- 

 gate into a trumpet-shaped polyp with tentacles and 

 then undergo a series of successive crosswise con- 

 strictions until it resembles a pile of saucers. One by 

 one these little saucers are pinched off from the par- 



ent polyp and swim away as little medusas, each 

 growing into an adult jellyfish. 



The true jellyfishes are usually divided into five 

 orders, and the first of these is sometimes set off as a 

 separate subclass because the members are not free- 

 swimming like the rest but live attached. 



THE SEDENTARY OR STALKED 

 JELLYFISHES 



These are the simplest scyphozoans, the stauro- 

 medusas or lucernids, which live attached by a 

 sucker, usually at the tip of a stalk that springs from 

 the center of the outer surface of a trumpet-shaped 

 or goblet-shaped umbrella. They inhabit sheltered 

 waters in the colder parts of the oceans, clinging to 

 eelgrass in sheltered coves or bays, to algae in rock 

 pools, or sometimes to rocks or shells. The margin 

 of the umbrella may be circular, but typically it is 

 drawn out into eight lobes, each tipped with a cluster 

 of twenty or more short, knobbed tentacles. Such 



The giant jellyfish, Ctjanea capillata, stranded at low tide. (Maine. Ralph Buchsbaum) 



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