46 The Under-Water World 



majority in that each polyp is enclosed 

 in a horny cup into which it can be with- 

 drawn when danger threatens or when 

 it is replete and desires an after-dinner 

 nap. 



The large jelly-fishes (Scyphozoa) are 

 well known to all and frequently intro- 

 duce themselves in an unpleasant fashion 

 to the sea-bather. When adult they 

 generally take the form of a large 

 umbrella-shaped disc which may measure 

 five feet across and weigh nearly 100 Ibs. 

 Like their close relatives the anemones 

 and corals, many hydroids and jelly-fish 

 menace the smaller inhabitants of the 

 ocean with that most insidious of all 

 weapons poison. They may not ob- 

 trude themselves, yet they are numerous 

 enough, and only their small size prevents 

 our native shores from being as perilous 

 as a tropical jungle. Magnify such crea- 

 tures fifty diameters and we have monsters 

 that could paralyse the strongest man 



