THE SCHOOL OF THE SHORE 41 



wafting minute creatures and nutritive particles 

 into its mouth. Professor Huxley compared 

 the acorn-shell to a shrimp fixed head-down- 

 wards, and kicking its food into its mouth with 

 its legs. But it is a peculiarly graceful kind 

 of kicking ! Many of them must expend much 

 energy before they sift out a meal from the 

 clear water. They live in castles ; but not 

 castles of indolence. The acorn-shells are 

 relatives and probably descendants of the 

 stalked barnacles which fix themselves to 

 wooden ships and floating logs. Like these 

 they are free-swimming in their early youth ; 

 but they fix themselves eventually by their 

 feelers and settle down. A rampart of lime 

 is formed round about, and the animal is 

 cemented down for the rest of its life. Not a 

 very exciting life, perhaps, but a very safe 

 one, for no waves are strong enough to wash 

 the barnacle from its rock. Sea-urchins have 

 meals of barnacle when they are tired of sea- 

 weeds, and dog-whelks also browse on them ; 

 but they hold their own well. Their eggs are 

 washed out by the tide and hatch in the open 

 water, and there we also find the transparent 

 feather-like moults of the adults which have 

 been cast in the pools. 



