Part 8

Oddly enough, most living creatures do not grow old. They simply live along till some other creature comes along and eats them up, or till the cold weather comes on and they freeze. A fresh egg is so soft that it hardly holds together; a young chicken is as tender as you please; while an old hen has to be boiled for days in order to be eaten at all. But an old fish isn’t tough; neither is an old lobster. Who ever heard a cook asking for little oysters, for the sake of getting them tender and juicy, or a fisherman preferring small fish? We like these the better, the older and larger they are. All animals, before they hatch out of the egg, are very soft. Afterwards they all grow larger and harder. But some stop growing big and continue to grow hard; and some stop growing hard and continue to grow big. The first sort grow old; the second do not.

Now when you come to think of it, about the only animals that grow old are the four-footed beasts, ourselves, and the birds. But the rate at which these various creatures grow old may be very different indeed.

Let us take a new-born human baby, and a new-born puppy, and a new-born mouse. All these are helpless little babies; and all three start immediately growing up and growing old. But while it takes six months for the human baby to grow to be twice as large as it was at birth, the puppy doubles its weight in nine days; while the little mouse, in the first twenty-four hours doubles its weight twice, so that at the end of its first day of life it is already four times as large as at the beginning.

At six months, the human baby, if he is very much up and coming, as you no doubt, my reader, were, can just begin to sit up without a pillow at its floppy back; it cannot walk a step, and it hasn’t a tooth in its head. But a six months puppy is a wiggly little beast, who runs away miles when he gets lost, chews up the family overshoes, and is well on the way toward losing his milk teeth. Meanwhile the mouse has grown up to be as large as he ever will be, has children of his own and probably grandchildren.

At five years the mouse is dying of old age. The puppy has become a sedate and middle-aged dog; but the baby is still a little child, just beginning to go to school, and still some years from losing its first tooth. At ten years, the child is young, the dog is old, and the mouse has become ancient history.

You musn’t think that the larger animals live longest. A horse is as large as six or eight men, but it is old long before a man first votes, and the birds, which are in general much smaller than the beasts, also in general live three, four, and five times as long. Even the elephant, thought to be longest lived of all beasts, lives no longer than we. But fish and turtles and crocodiles and shell-fish and the like, which are neither beasts nor birds and grow big without growing old, may outlive even parrots, elephants and men.

I dwell upon this at some length because there is no doubt that just as the dog grows old more slowly than the mouse, and the man grows old more slowly than the dog, so some men grow old, more slowly than others. Some people have used up their lives and are old at fifty or sixty; some are still young and hard at work at seventy and eighty. Now it rests partly with ourselves which we shall be. Five is not a large number to multiply by. But five times your present age, my reader, will take you well up to middle life. In no small degree, it is for you to choose whether you will come to five times your present age with the best part of your lives over and done with, or with the best part still to come. What, in general, your fathers and mothers are telling you is right and teaching you to do, will contribute to the one result; what in general they are telling you is unwise and wrong will doom you to the other. That indeed is how we know that some things are right and others things are wrong. People have tried, many times over, and found out, to their profit or to their cost.

Why We Grow At All

Did you ever stop to think how extremely convenient it is to have two parents? Mama stays at home and takes care of the little children, reads and sings to them, tells them stories, puts them to bed, spanks them when they are naughty and kisses them when they are good. Indeed, you couldn’t get on very well without Mama. Neither could you get on very well without Daddy. Daddy doesn’t seem so important as Mama; but if Daddy didn’t go to work every day, and earn money for Mama and their little boys and girls, where would house and food and clothes and birthday parties and music lessons all come from?

Suppose there were no Mamas at all, but only just Daddies. Then of course there would be no aunties, nor nurses nor cooks nor big sisters nor kind ladies in the next house. There would be only just men; and half the men would have to stay home from the office to take care of the little boys of the other half, and then their work wouldn’t get done, and there would be no end of trouble.

It would be almost worse if there were only Mamas and no Daddies. For then all the Mamas would have to go out to work; and even when they could earn enough to hire a nurse, which I am afraid would not be often, the best of nurses isn’t like Mama. So it is really much better as it is, when we have both fathers and mothers, one to work abroad, and the other to work at home and take care of the children.

In fact, this arrangement is so much better than any other that pretty much all the living world has adopted it. You know the ears of corn which we buy in August and September and eat off the cob. You know too how it comes from the shop, all wrapped up in soft green husks, with the long silk hanging out of the end, that little girls in the country use for dolls’ hair, and ridiculous little boys try to smoke in pipes. The ear is the mother corn, and the kernels wrapped snugly away in the green husk are her children. Or rather they are her eggs, with the little corn plants inside, almost ready to be dried over winter and be planted and start life for themselves. Each kernel of corn has one fibre of silk, which is joined to it at one end and hanging out of the ear at the other.

The ear, then, is the mother of the corn. Its father is the tassel at the top of the stalk. From each branch of the tassel hang many tiny brown bags, each about as large as a grain of rice, and each filled with a very fine brown dust. This dust is called pollen. And unless a grain of this pollen falls on each thread of silk of each ear, then the kernel at the other end of the thread will never grow to full size and never become a seed; but will always remain small like the undersized kernels at the end of the ear. If the tassel is cut off; or the silk pulled out; or the ear tied up in a paper bag, then the ear forms no proper seed.

Sometimes, on an ear of sweet corn, one finds a few kernels, or a single kernel only, that instead of being white like the rest, is yellow. This means that somewhere in the neighborhood, it may be miles away, somebody has planted a field of common yellow corn, which we make into corn meal, but do not eat off the cob because it isn’t sweet. A grain or two of pollen from this yellow corn has been carried by the wind and fallen on the silk of an ear of sweet corn. So the father of that particular kernel is yellow and its mother white, and the kernel is colored just as if a white woman had married a Negro or an Indian.

Different plants manage these things differently. The ancient Egyptians, who lived on dates much as we live on corn and wheat, used to plant orchards of date palms as we plant orchards of our fruits. Every year, at the time when the cultivated date trees were in blossom, the Egyptian farmers used to go out into the desert, cut branches from certain wild palms which never bore fruit, and carry them in procession thru their date orchards. They did not know why they did this. They only knew that if they omitted the ceremony for a single year, that year they got no fruit. We know now, of course, that the date-bearing palm is the female tree; and the wild palm which doesn’t bear anything is the male. The procession with branches thru the orchards simply brought in the pollen.

Most plants, on the other hand, not to take any chances, have seed and pollen in the same flower. Many too, instead of relying on accident and the wind to carry one to the other, are arranged so that insects and humming-birds, in seeking food, shall make the transfer. Some, few, however, like the willows, have seed and pollen on separate trees.

The water plants manage in much the same way. They, for the most part, turn loose in the water what in them corresponds to the pollen, and waves and currents carry it to the young seeds. The simpler water animals, sponges and sea-anemones and shell-fish do much the same. While the female sea-urchin or star-fish produces eggs as small as dust, the male produces a still finer pollen-dust, which we call milt or sperm. If one grain of this happens to float against an egg, the egg at once begins to change to a young animal. Otherwise after a week or so the egg dies and that is the end of it. Of course, under these conditions, the chance of egg and milt getting together is pretty slim, and the waste of eggs is enormous. So the fishes, which can move about, have a much better plan. When the female salmon, for example, swims up the rivers to leave her eggs among the gravels in the swift water, the male goes along with her. After she has laid her eggs and gone away, along comes her mate and scatters milt over them. So the salmon egg is pretty sure to grow; and the salmon can afford to have few eggs and larger, and so give her little ones more yolk to live on and a better start in the world.

The bees have a still better device. The single queen bee, as everybody is supposed to know, lays all the eggs of the hive. When the queen is young and the new swarm is just starting, she annexes enough of this pollen-milt-sperm to last her the rest of her life, and stores it up in a little sack. Then whenever she lays an egg, all she has to do is to give this sack a squeeze, press out a little of the contents, and start the egg growing into a new bee.

Strangely enough, however, altho this practice of having two parents is so very common among both animals and plants, and so universal among human beings, it is not, so far as we can see, at all necessary. Potatoes are thick underground branches, and not seeds at all. Yet we plant them and they answer exactly as well. Many lowly creatures, like the yeasts, the bacteria, the infusorians of stagnant water, and the like, never have anything resembling seeds or eggs. There is a parent. The parent splits in halves. There are two children. And where is the parent?

Among the common green plant-lice which swarm on the leaves in the summer, the males all die early in the season. After that the females go on laying eggs, and these hatch more females which lay more eggs, for ten and twelve generations, before the cold weather comes on and some of the eggs begin to hatch out males once more. They get along exactly as well when each insect has only one parent, as when it has two.

In the case of the queen bee, if while the egg is being laid she squeezes the sack, then the egg hatches out a worker, which has therefore, two parents. But if she does not, then the egg hatches out a drone, which has only one. There are many other strange facts of this sort, which have been known for a long time, but which nobody has yet been able quite to understand.

Some facts still stranger have recently come to light. It has found that in the case of many sea creatures, star-fish, sea-urchins, shell-fish and others, that if the eggs are kept in common sea water, but kept carefully away from any milt, they soon die, and never grow up at all. But if any one of a considerable number of substances is added to the water, sugar, salt, acids, and other things, then the eggs, tho they still have only one parent, proceed to grow into the proper sort of little sea creatures, just as if they had two.

It is really a great mystery; the most that any one can say is that the eggs are there, but something in the water, or the absence of something, stops their growing. Add sugar, salt, acid, or milt and they grow. In the case of the land animals, this something is probably in the blood—for as you know, the blood is salt like the sea, and in many other ways much like it.

At any rate, this is practically a most convenient arrangement. A mother bird, for example, is herself born with all the eggs she is ever going to lay already formed inside her. But something in her blood keeps those eggs from growing bigger than pin heads. They don’t grow into proper eggs, that can hatch into little birds, until the mother bird gets a mate to help her build the nest, and to feed the little birds when they come, and sometimes to feed her too. Then some of them do grow up and hatch; and the two old birds take care of them.

But as I said, it is all a very great mystery, which the wisest men do not yet completely understand, and little boys and girls can hardly expect to understand at all.

XII

Things That Do Not Have To Be Learned

So far in this book, we have been learning about the body. We know something about the wonderful life-jelly of which all living things are made—how it is itself the soft parts of plants and animals, and how it builds for itself the hard shell and bones and wood, which are its supports and its tools. We know, also, something about how each particular animal or plant or human being starts as a minute fleck of this life-jelly, grows to be, first a seed or an egg, and then a full grown animal, a man, or a tree. We know, too, something of the living bricks which build the bodies of living creatures; and something of the difference between young creatures and old ones. More than this, I trust, we have learned that all this curious information is not to be looked at merely as something interesting or amusing; but that like all the teachings of science, it is something that will help us to live wisely. For as we come to know, we ought also to learn to do; and while we are finding out something about living things, we ought also to be finding out something about living.