104 THE SEA-SHORE 



begins to swim they open out and wave up and 

 down in the water; for they are really tiny 

 paddles, by means of which the nereis rows 

 itself along. Altogether there are about four 

 hundred pairs of these little flaps, which move 

 in perfect time together, just like the oars of 

 a well-rowed boat. Perhaps you may have seen 

 a boat-race, and you noticed, no doubt, how all 

 the eight oars rose and fell exactly at the same 

 instant, as regularly as if they were moved by 

 machinery. Well, imagine a very long boat 

 indeed rowed by four hundred little rowers 

 instead of only by eight, and each with two 

 oars instead of one, and then you will have 

 some idea of what a nereis looks like as it goes 

 swimming through the water. 



This curious worm does not live only under 

 stones, for it is sometimes found hiding in the 

 whelk shells which are occupied by hermit crabs, 

 the worm and the crab living in the same shell 

 together, and never seeming to interfere with 

 one another. 



