THE IMPENETRABLE SEA 



Many creatures of the shore which seem stationary 

 have some power of movement. The sea-urchin and the 

 starfish, with their myriads of tube-Hke feet (somewhat 

 resembhng the rubber "dummies" with which Victorian 

 mothers pacified their babies) are almost agile animals as 

 they move from place to place. When compelled to do so, 

 the limpet can move house by simply walking away with 

 it. But all these ambulatory exercises are limited in area 

 and most encrusting animals cannot do otherwise than 

 "stay put". If danger threatens them, all they can do is to 

 "shut the door" and hope for the best. 



But the common barnacle does better than this — it 

 takes a supply of air into its house before locking up. It 

 is a tiny crustacean which, when the tide is in, stands 

 upside-down in its box-like dwelling, which is made of 

 plates of lime, and switches food towards itself with 

 its slender legs. The tide recedes, and it shuts the doors — 

 four of them, which are tightly-fitting valves. But as it 

 does so it is careful to entrap a bubble of air and also 

 sufficient moisture to keep its gills damp. 



When you are walking along the shore, just after the 

 tide has turned from the rocks, you may hear (all around 

 you, if there are sufficient barnacles in the area) the 

 "whispering" of the little creatures: a faint crackling 

 sound. You may have precipitated it by the vibrations of 

 your walking feet. The sound comes from the closing of 

 countless thousands of those doors in the tiny houses, 

 combined with the rupture of the air-bubbles as the 

 barnacles make themselves snug. Sealed in their homes, 

 they may remain shut up for days or weeks, not taking 

 any food and conserving the air by "breathing" hardly at 

 all. 



We cannot leave the armoured hosts of the sea-shore 

 without hearing what the oyster has to tell us about itself, 

 although its name has become proverbially associated 

 with reticence. It is an amazingly prolific creature. For 

 instance, the American oyster may produce hundreds of 



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