COASTLINES 



Oysters die strange deaths. One of the most curious is 

 when their own descendants pile upon them in such 

 prodigious numbers as they he on the sea-bed that those 

 underneath are stifled in their enforced imprisonment. 



Of the innumerable battles which take place incess- 

 antly in shore waters, the struggle which ensues when a 

 starfish attacks an oyster is one of the most remarkable. 

 The starfish opens the attack by straddling the oyster and 

 attaching its feet to the upper valve of its shell-case. It 

 tugs and tugs at the upper shell, using all its strength 

 against the oyster, who tries desperately to keep its door 

 shut against the marauder. Eventually, no matter how 

 long the struggle, the starfish wins the unequal battle. 

 The oyster shell-case is forced open and the starfish turns 

 its own stomach inside-out and forces it into the shell. In 

 that position, with the stomach inside-out and the oyster 

 helpless, the contents of the shell-case are quickly ab- 

 sorbed and digested. The starfish crawls away at last, 

 having withdrawn its stomach, leaving the empty shell. 



For every curious or pretty shell, preserved in some- 

 one's home, countless millions lie crushed and broken on 

 the shores of the world, or pressed down by the weight 

 of the waters, on the sea-beds. Yet every shell was once 

 the armour of a living creature which was born wrapped 

 in a transparent mantle of singular beauty. Each mantle 

 has the power of extracting lime from sea water, which 

 it builds up into the creature's adult shell, usually colour- 

 ing it with rainbow-like hues in the process. 



This wonderful mantle which nature has given to the 

 Mollusca — the name means ''soft-bodied" — may be seen 

 in any common animal that wears a shell, such as the 

 oyster or periwinkle. The way the mantle builds up the 

 protective armour is instanced in the periwinkle's 

 development. When it was very small it was no larger 

 than a pin's head. As its body grew it needed a larger 

 home. So the creature pushed some of its soft mantle 

 out of the aperture of its shell, where it spread out a 



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