As we have seen all the way through—and will see a great deal more, the more we look carefully at the picture in Nature's wonder book, the higher forms of life keep summing up the lives below, and foretelling higher lives to come.

The earthworm, with his joint-ringed body, foretells the crawfish, with his jointed shell; the crawfish foretells the fish, with his tail set the other way, and the shell made into scales. The bird is a fish with true scales only on his legs, and the other scales changed to feathers and feather quills, the fins changed to wings and the tail turned back flat, like the lobster's.

You know, when you are listening to a story, if you happen to get to listening to something else for a few moments, how the rest of the story gets all mixed up? Then you ask mama to tell part of it over again.

Mother Nature seems to want to be so sure that we will not miss the smallest part of her story—the story of lower lives growing into higher all the time. So she keeps going back and telling it over and over again, whether we ask her to or not.

The higher the form of life, the more features of all forms of life it has in it. The crawfish, for example, couldn't show us what wings looked like because his people and their near relations didn't have any wings. Nor Mr. Fish couldn't show us what feathers are because he never was a bird. But the bird can show us the fins of the fish in his wings, the fish's scales on his legs, the jointed rings of the earthworm in his backbone, the whole earthworm in his intestines.

Not only because they are made of the same stuff, and because they have similar habits, are animals that look so different supposed to belong to the same great family, but there are many "connecting links" between different animals, like the fish that fly. Go far enough down the tree of life and you will find where one branch of the family is connected with some other branch that seems as different as can be.

Fish and birds, the owl and the pussy cat, all belong to one great family—the back-boned family. But among the back-boned family those that suckle their young, as the cat does, are higher than those that do not. Animals and people learn and go up higher in life, in proportion as they are sociable. A mother and her babies are sociable with one another. They love each other and they teach each other. The mama cat learns to be shrewd and careful because she has other little mouths to feed and lives to protect, beside her own. It is just as true in the insect world. For example, the ants and spiders are both very bright. They know how to do many wonderful things, and these wonderful things are most of them done in taking care of their eggs, and the babies that are hatched out of these eggs.

And do you know about how these ants keep other insects for cows? These "cow" insects are the little green lice that you find on plants. They are not good for the plants but they make good "cows." They give down a kind of honey dew, just as the old cow gives milk for her babies. Don't you wonder if this honey dew is meant for the babies of the aphis or plant lice? If it is true that they do give this sweet milk for their babies, they are really mammals, too, and when the higher animals feed their young in this way they are simply repeating something that is done away down in the insect world.

Another odd thing about these aphides is that sometimes they lay eggs, and sometimes they bring forth their babies alive, already hatched. It is when they have wings that they lay eggs but have no milk, and in the state that they bring forth their young alive, they have this milk. So the more we think about it the more it seems as if these little bugs are mammals, too.

But whether the aphis is one kind of a "bird" that suckles its young and so seems to want to remind us still more of the relation between birds and mammals, it is certain that there are egg-laying animals that suckle their young. One of these is the spiney ant-eater.

Another is the duck mole. You can see from his name that he must be something like a duck and something like a mole. He burrows in the ground and suckles his young like a mole and he has a bill and lays eggs like a duck.

Then there are fish that suckle their young. They might be called fish because they live in the water, and swim like fish ; or they might be called sea-lions because they have sharp teeth and eat meat like dogs or lions, and suckle their young as the lioness does her cubs.

As we find some mammals laying eggs—most of them seem to have dropped their egg-laying habits with their wings—so we find some mammals that have wings but that do not lay eggs. Thus the great families of nature seem to be held together on both sides; just as you keep yourself in a tree by holding on to two different limbs, one with the left hand and one with the right. Bats have wings, as you know, much like the wings of a bird, and much like the fins of a fish, with great spiney ribs running through them. But bats suckle their young just as Mama Dog does her puppies.

Notice how, in still another way, Nature seems to want to make sure that we see that we are all relations and should be kind to one another and find joy in studying each other's lives and in making these lives as happy and helpful as possible.