THE SCHOOL OF THE SHORE 39 



grappling-cells. Just as we draw back our 

 finger from a hot plate without even willing 

 it, because of a circuit between nerve-cells that 

 feel, nerve-cells that command, and muscle-cells 

 that obey, so the sea-anemone folds its tentacles 

 about an incautious worm. This is called 

 reflex action. The sea-anemone may be 

 deceived by giving the tentacles a little roll 

 of wet paper to catch ; but after it has been 

 cheated twice or thrice it has had enough and 

 will not close up any more. Sometimes it 

 catches too big an animal, like a periwinkle, 

 which struggles hard and bursts through the 

 enswathing tentacles. The sea-anemone can 

 flourish for a long time without more than 

 microscopic food ; it might be called an easy- 

 going feeder. One has been known to live 

 for sixty years. 



Right up to the high-tide mark on rocks, 

 pillars of piers, stray pieces of wood, and even 

 on living animals, like crabs, we see a crusting 

 of rock-barnacles or acorn-shells. When the 

 tide is out the roof of the rampart that encloses 

 the animal is kept tightly shut ; but as soon as 

 the water, or even the salt spray, reaches it, 

 the acorn-shell opens its four valves. When 

 it is covered with water it begins to feed with- 



