You would think, perhaps, that when a lug worm bores its way through the loose sand, the sides of its burrow would fall in behind it as fast as it passed along. But from the surface of its body it pours out a thin, sticky liquid which binds the sand together, and forms a kind of lining to the burrow, like the brickwork of a railway tunnel. The burrow is generally about two feet deep, and the worm always lives in it with its head downwards. The worm itself, when fully grown, is from six to ten inches long.
PLATE XXXIV
THE NEMERTES (1)
This is quite one of the most curious creatures to be found on the sea-shore. It hides under large stones at the bottom of the pools, and looks rather like a tangled boot-lace. But it is really a kind of leech-like worm, and the wonderful thing about it is that it can stretch its body out to almost any length, just as if it were made of elastic. It always does this in catching its prey, which it seizes by means of its sucker-like mouth, which has a kind of beak inside it. Then it “plays” its victim just as an angler “plays” a fish, sometimes stretching its body out to a length of fifteen or twenty feet, then drawing it in again to a length of three or four, and so on over and over again, until its prisoner is quite exhausted, when it proceeds to devour it.
PLATE XXXIV
THE NEREIS (2)
The Nereis is a very common sea-side worm, and you can nearly always find it by turning over the stones on the shore as the tide goes out. It is brown in colour, with a dark red line along the back; and if you look at it in the sunlight you will see flashes of bright blue playing over the surface of its skin. And underneath it is of the most delicate pink, with a glossy look which reminds one of mother-of-pearl. It is one of the largest of all the worms, for it often grows to a length of nearly two feet.
If you examine the back of a nereis, you will find a row of little tufted organs running right along it. Each of these really consists of two little flaps, which are folded together as long as the worm remains still. But as soon as it 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.
