234 DAHLAK 



however to the class hidrogoa (the same class to which jelly- 

 fish belong), but with a calcareous skeleton similar to the 

 madrepores, it is easy to recognize the yellow-ochre colour 

 of the millepores or fire-coral. They are to be avoided because 

 of the stinging power of their polyps. At the slightest contact 

 they shoot out a long spiral filament which acts like a 

 minute injection needle. The poison transmitted has a 

 paralysing caustic action. The effects on men are similar to 

 those produced by the poison of big tropical jelly-fish. The 

 millepores flourish most of all in clear water. Their colonies 

 build ramifications to a height of six feet in shallow water 

 and make swimming, even on the surface, a difiicult opera- 

 tion. 



