THE SCHOOL OF THE SHORE 41 
wafting minute creatures and nutritive parti- 
cles into its mouth. Professor Huxley com- 
pared the acorn-shell to a shrimp fixed head- 
downwards, 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 cas- 
tles; 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. Nota 
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. 
