228 RADIATES: JELLY-FISHES. 



some of them cause a stinging sensation when they 

 touch our flesh ; hence they are often called Sea-Net- 

 tles. They are also as often called Medusae. Their 



Fig. 472. Jell y-Fish. 



common name, Jelly-Fish es, was given on account of 

 their jelly-like appearance and substance. 



If we examine the structure of Acalephs, we find 

 a cavity, which is the stomach, hollowed out of the 

 mass of the body, and this cavity has an opening 

 which serves as a mouth ; the edges of this opening 

 are turned outwards and prolonged into delicate fringes. 

 And there are tubes which radiate from the centre of 

 the body and unite with a tube at the circumference. 



The kinds of Jelly-Fishes are numerous, and they 

 vary in size from those scarcely visible to those which 



