Now suppose that you carry the stone home with you, just as it is, and put it into a vessel of sea-water. After an hour or two you will find that the little scarlet objects have been poked out of the tubes, and that they are really tiny stoppers, just like little corks, which exactly fit the entrance when they are pulled inside. And you will also find that a plume of feathery objects, which are also bright scarlet in colour, is projecting out of the mouth of each tube. These red plumes are the gills of the worms, and they will often remain spread for hours at a time. But if you startle the animals—if your shadow falls upon them, for instance—they will draw themselves down into their tubes in about half a quarter of a second, and every tube will be corked up by its tiny stopper, just as before.
1. THE SERPULA.2. SERPULAS IN TUBES.
On the sides of its body the serpula has tufts of little bristly hairs, just as the sabella has, which allow it to move up and down its tube. But in order to enable it to draw itself back as quickly as possible in moments of danger, it has a row of little hooked teeth on its back, by means of which it can take a firm hold of the lining of its burrow. I think you will be rather surprised when I tell you how many of these teeth there are in the row. Just fancy! Each serpula has between thirteen and fourteen thousand!
If you look at the oysters in a fishmonger’s shop, you may often see the tubes of these curious worms fastened to the surface of the shells.
PLATE XXXIII
THE TEREBELLA (1)
This is another of the worms which live in tubes. You can generally find its wonderful little dwellings by hunting in the small puddles of sea-water which are left on the sands when the tide goes out. And you can always tell them from those of the sabella and the serpula by the curious little fringe round the entrance, which is made of the tiniest grains of sand fastened together into slender threads. The tube itself is made of larger grains, and is so tough and leathery that you can give it quite a hard pull without breaking it. But as it is at least a foot long, and is nearly always carried down underneath rocks or big stones, you will not find it at all easy to dig it up. And the moment that you alarm the little animal inside it always makes its way right down to the very bottom of its tube.