22 THE HAUNTS OF LIFE 



it does not evaporate, and the limpet is safe, 

 too, from being injured by the waves. But it 

 is not altogether safe from other animals, for 

 some birds, especially the oyster-catcher or 

 sea-pie, have discovered exactly the kind of 

 sudden sharp stroke of the bill that is needed 

 to knock a limpet off its rock, and once it has 

 let go its hold it is a helpless victim. When 

 the tide covers the limpet's rock it relaxes its 

 hold and slowly moves off on its foot to the 

 nearest seaweed patch where it cuts, with the 

 long, toothed, rasping ribbon or file in its 

 mouth, the grassy blades on which it feeds. 

 Before the tide has ebbed it makes its way 

 back to its rock, if it has not wandered too far 

 and lost its way, and fixes itself in the exact 

 spot in which it was before. In some cases it 

 keeps to this spot so persistently that a little 

 pit corresponding in size and shape to its shell 

 may often be seen in the rock. Where all the 

 rock is smooth the limpet does not trouble to 

 return to its starting-point, for every spot is 

 very much the same. 



Some molluscs, whose shells are not large 

 enough to enclose them comfortably, or to 

 protect them effectively, have learnt to bury 

 themselves in the sand, and so to secure mois- 



