While the sponge is like an animal, in eating other little animals and plants, it is like a vegetable in that it cannot move around. It is rooted to one spot. The sponges grow so thickly that they often make perfect forests on the rocks, on the bottom of the sea. When the sponge is taken from the water it is covered with what seems to be a mass of jelly. This is its flesh, and the flesh is made up of the little cells with tails that I have been telling you about.
A sponge as it appears attached to the ocean bed. The little animals inside the horny skeleton stick hairly-like tails out into the water to catch their food.
Just as if you might forget—although it seems so plain—that this sponge is made up of little creatures like the infusoria, and has become a higher order of animal because all these little animals formed into a society and worked together, the sponges increase by laying eggs; one-celled eggs. These eggs first turn into simple little animals with paddles all around them, like the infusoria, and they swim around by themselves, for awhile, before a number of them settle down together to form a sponge. They are like boys that go out into the world awhile to learn what it is like, and then join other boys and go into business together.
As we go along you will find nature continually "saying her piece" over again, from the beginning, as if to be sure she gets it right. And, also, I think, she may do it to be sure that we catch the idea of what wonderful things all of us can do in this world, if we will do each little thing, build each little thing, as well as we can, and keep looking upward as we build.
