GENERAL ZOOLOGY 



Fig. 10.11. A scyphomedusan jellyfish, Cyanea. (Photograph by George Lower.) 



also gonozooids, medusa-like individuals which are not released but produce 

 gametes. The siphonophores are considered to have diverged from the main 

 hydrozoan stem early in its evolution. 



THE CLASS SCYPHOMEDUSAE 



Most of the jellyfishes called hydromedusae are small, like Gomonemus, or 

 smaller. The jellyfishes comprising the class Scyphomedusae are mostly of a 

 larger size; individuals of the species Cyanea arciica (Fig. 10.11) have been 

 recorded with a diameter of 12 feet and tentacles over 100 feet in length. 

 The amount of solid or living material in such individuals would be small, 

 however, because jellyfishes are composed chiefly of water. The bulk of their 

 substance consists of the "jelly," which in these forms is a gelatinous mass 

 conspicuously provided with cells resembling connective-tissue elements of 

 higher animals. The jelly itself may thus be considered as intercellular ma- 

 terial, comparable with the fibrous substance of connective tissue or the 

 ground substance of cartilage. In scyphomedusans specialized organs of 

 equilibration, termed statocysts, are located at intervals around the margin 

 of the bell; these sense organs are important in the free-swimming locomotion 

 of jellyfishes, and similar though simpler statocysts occur also in hydromedusae. 



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