THE IMPENETRABLE SEA 



curious tricks with them. They can bite off chunks of 

 coral which would blunt an ordinary chisel, crunching 

 the stuff in their jaws as though it were pieces of candy. 

 They can even crack the tough shells of oysters and 

 devour the contents. 



The file-fish is truly a clown, for he takes part in an 

 extraordinary series of happenings, as though he were 

 one of a group of comedians scoring off each other in a 

 stage turn. For the file-fish preys on the oyster, but the 

 game doesn't stop there — the ray preys on the file-fish, 

 so that there is a kind of predatory merry-go-round. A 

 certain thread-like parasite plays its own part as one of 

 the actors in this ''crazy gang". It passes the first phase 

 of its existence in the body of the file-fish. Along comes a 

 ray and devours the file-fish so that the thread-like 

 parasite passes into the body of the ray. There it enters 

 its next phase of existence and lays its eggs. When these 

 little parasites hatch out they pour out from the body of 

 the ray and enter the open shells of oysters, where they 

 really begin their brief lives. The sensitive oyster protects 

 itself against these unwelcome parasites. The irritation 

 created by their presence causes the oyster to pour out 

 the smooth, shining, iridescent substance which we call 

 ''nacre". 



Of course any foreign body in the oyster may produce 

 such irritation, but we are considering the life-cycle of a 

 parasite which has just left the body of a ray in consider- 

 able numbers. The little worm pays a terrible price for 

 its temerity in trespassing into the oyster's sanctuary — it 

 is literally buried alive in the nacre as it hardens around 

 it, and becomes a pearl. Some of the most costly pearls 

 which adorn the throats of lovely women are the tombs 

 of long-dead parasites. 



Dolphins are not fishes, but mammals. They are often 

 confused with porpoises, in fact one popular encyclo- 

 paedia says : "more commonly called porpoises". But the 

 nose of a porpoise is a blunt, rounded snout, and is not 



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