Now that our snail has been good enough to put out those four horns of his, let us ask what purpose they serve, and why they are placed' where they are. The answer is very simple; these "feelers" are to the snail instead of arms and legs; and the upper pair have eyes at the end, so that the wary little traveller, as it drags itself along a broad cabbage leaf, leaving a slimy track behind it, can tell, both by sight and touch, what obstacles may lie in its path. I don't know whether you have ever seen the eggs of snails; I have not, but I have heard that they are about the size of peas, and are buried in the earth, as the crocodile's eggs are buried in the sand. Of the many families of Ringed or Jointed Animals, we will choose the Crabs and Lobsters first. They are encased in armour of shell, and this has given to them and their relations the name of Crustaceans, or Crusty creatures, because what bones they have are outside, not hidden beneath the flesh. But unlike the snail's house, which grows with the growth of its inmate, and unlike _our_ skeleton which grows as _we_ grow, this close-fitting armour does not increase in size, nor is it elastic enough to expand, but every year one coat of mail is cast off, in a way not unlike the sloughing of the serpent, to make room for a fresh soft suit. This new suit soon hardens, and the creatures embrace the opportunity to make a little progress in growing, which they do by fits and starts, not continuously; for the shell, when once hardened, gives them no room to increase in size--they have to wait till next year! The long pointed claws of the crab and lobster are easily broken, and sometimes lost altogether, so that the power which they have of growing new ones is a wonderful provision for their life among the rough rocks and tangled sea-weeds. One of the crusty creatures you know well enough, and you can find it without going to the seaside, I mean the wood-louse, which I used to hear called a "carpenter" when I was a child. In damp places, you can hardly turn over a mossy stone, or pick off a bit of bark from a fallen tree, without disturbing a whole colony of these slate-coloured creatures, with their mailed coats, made of ten rings, or plates of armour. They seem to know the use of their armour well enough, for if disturbed you will see them either scurry off as fast as their many little feet can carry them--and they are able to run forward or backward at pleasure--or else roll themselves up into tight balls, so that feet and head and feelers are all safe, under the ringed shield which God has given them as a defence and protection.