The ordinary tadpole, if well fed, astonishes and delights his young keepers in a few days by putting forth a pair of tiny hind legs, which generally trail behind him when he swims, though he often kicks with them, perhaps for exercise. He grows larger and his legs longer, and one day a row of fingers may be seen peeping out of his gill slit, as though out of an armhole, and then he will thrust out a forearm, then another from the other gill slit. After this, changes are rapid, and his keepers should put a stone or some firm object in the water, reaching above the surface, so that he can climb up into the air; for now his lungs are rapidly forming, and soon he can no longer breathe by gills. At this stage, his tail begins to disappear. It does not fall off, as some think, but its substance is absorbed into his body until no tail is left. Finally, his head changes its shape, his baby mouth is replaced by a wide frog mouth, his eyes stand out with projecting lids, his ear-plates showing back of them, and we have a full-grown frog.
To the child who understands the origin of the fish eggs a few questions which he can easily answer himself will be enough to call attention to the important differences, and also to deepen the impression of the unity of life as expressed in flower, fish, and frog.
The ova of the frog develop in an ovary exactly as do the ova of a fish; they develop in the same way and at the maturity of the animal. The fertilizing cells develop like those of the fish. In both cases, the reproductive elements are laid, shed, or born, when the time comes.
Before the eggs of the frogs and toads are laid they have no alb.u.minous covering. The moisture that envelops them swells up into the jelly-like ma.s.s upon coming in contact with water.
There are important differences between the frog and the fish. The frog is a more complex animal and, so to speak, more difficult to create, and it lays fewer eggs. Since there are fewer eggs they must be more carefully fertilized; that is, the fertilizing material must be sure to come in contact with all of them. Consequently at the moment when the eggs are finding their way into the water they are fertilized; not within the female body, but just as they are leaving it.
The child accustomed to notice what he sees will observe the paired frogs in the pond. He can be told that they take this position just before the eggs are laid so that every egg will surely be fertilized. In the amphibious animals the relation of the two parents is closer than in the fishes, but yet there is no union between them, that appearing only when it is necessary. The stern law of necessity governing every step of the reproductive function may be made very impressive to the young mind; also _the reign of law_ throughout life.
To explain frankly, simply, and scientifically such phenomena as that of the paired frogs will tend to rob them of dangerous interest. Not to speak of them will not prevent the child"s seeing them, and his imagination may foster much less wholesome thoughts.
There are frogs and toads that care for their young, but parental affection in this form of life is rare. The eggs are laid in a favorable spot, and then left. Toads as well as frogs lay their eggs in the water. The instinct of the toad leads it to seek the water at the egg-laying season, as its tadpole, like that of the frog, can live only in the water. At other seasons of the year the toad does not enter the water.
Frogs" eggs are laid in compact ma.s.ses, while toads" eggs are laid in strings or ropes; and in this way they can be recognized, though after they have once hatched the tadpoles of both are so much alike that they cannot be told apart. Sometimes the children will be disappointed because the tadpole does not change into a frog nor yet into a toad. It gets its four legs but does not lose its tail; it never loses its tail.
In short, it is not a frog or a toad, but a salamander or water-lizard, which lays eggs similar to those of the frog, and whose young upon first hatching look very much like young tadpoles.
If eggs are found in a pond where frogs are not heard or seen, they will almost always turn out to be the eggs of a salamander.
X
THE BIRD
From the flower to the bird is a step easily taken if the parent prefers to omit the intermediate steps, or, after the story of the bird has been told, the stories of fish and frog can follow as occasion offers, instead of preceding it. The bird is peculiarly valuable in teaching the origin of life to the child, since in it we have such highly developed home and family instincts, the father bearing his share of the burden, ill.u.s.trations of which are rare in the lower forms of life. As everywhere else, the best starting-point is with the life and interests of the bird itself, and for this caged birds are far better than the free ones, even though they may be only the sparrows and pigeons of the city streets.
The flight of birds is that which particularly interests children as well as every one else. Birds will soon learn to come to a place where they are fed regularly; and the style of flight, depending upon the size and shape of the wing as well as the shape of the bird"s body, is a very interesting study. Many a country child knows the common birds by their flight even when the bird is too far away and moving too fast to be distinctly seen. What he generally does not think of is _why_ the bird has this peculiar flight, and to have his attention called to it may increase his interest in watching the living bird.
Whatever increases the boy"s interest in the live bird tends to decrease his desire to make it a dead bird; and the numerous good bird-books, as well as the subst.i.tution in so many cases of the camera for the gun, has tended to preserve the lives of the birds and to create a sentiment in favor of their preservation. If the young child is taught to watch the birds and care for them, he will not often, when older, thirst to take their lives.
While the flight of the bird may engage the first interest of the child, its manner of eating and drinking is worth attention, and the nature of its food is of the greatest importance. The shape of the bird"s beak will decide, at least in a general way, the kind of food it eats; and a little study of birds will convince any one that all birds are useful to the agriculturist, either as destroyers of noxious insects or of weed seeds. While some birds swallow the seeds whole and pa.s.s them again unharmed, thus spreading the plant, others crack the seed coat and eat the contents, which of course destroys the seed. Even where the birds are the means of sowing seeds they do more good than harm; for the seeds thus sown are not often harmful, and those same birds destroy a vast number of noxious insects. Even owls and hawks, by destroying mice in the farmer"s fields, do him a service that much more than compensates for the loss of an occasional chicken.
While the birds are of inestimable value to the farmer and to any one who has a garden, their influence on our lives in another direction is also very great, as difficult to estimate perhaps, as that of flowers.
Who can doubt that these little brothers of the air are one of the most civilizing and elevating factors in man"s daily life? Their song, their flight, their thousand and one charming or entertaining habits, their strong expression of personality, their poetical and mysterious comings and goings, appeal powerfully to the higher imagination.
The migration of birds is alone enough to fill the mind with enchanting dreams. To know that every night in late summer and in autumn there is a stream of birds moving high in the air along the line of the sea-coast and of the great valleys is enough to awaken fancy. This winged procession moving along its aerial highway is made of the small and timid birds that dare not fly by day for fear of hawks and other enemies; they may be as high as three miles above the surface of the earth, their height being estimated by watching them through the telescope as they cross the surface of the moon. Imagine looking through the telescope at the face of the full moon some night and seeing an endless procession of little birds speeding across its shining face!
The amazing power of birds to see and hear, and, most interesting of all, their nest-building habits are calculated to arouse the wonder and admiration of every observer. What child would not watch with intense interest the bringing of the straws or other materials, and the deft weaving of them into the home which is presently to receive the precious eggs? Even the city sparrow may here be a boon to the mother.
Sufficiently encouraged, it will accommodatingly build almost anywhere.
The child who knows the story of fish life and frog life will need little telling here, and that is one argument in favor of taking all the gradual steps from flower to bird. By this time the main ideas are firmly lodged, the child will readily draw his own conclusions as to the rest; but there are one or two facts connected with the origin of the bird which are of great value in fixing the idea of _necessity_ which is at the foundation of all reproductive phenomena. Everything is as it is because it is necessary that it should be so. In the frog the higher development made necessary greater economy in the production of the egg and the fertilizing cell, and this economy of material necessitated the more certain fertilization of the egg.
In the bird a great step upwards has been taken. Here we have something much more complex in every way. The frog was cold-blooded, comparatively sluggish, and comparatively simple in structure. The bird is warm-blooded, intensely active, and very much more complex both in bodily structure and in mind development. Here the reproductive activity is yet more economically conducted, and instead of thirty or more eggs, the bird produces often not more than six in a season, and even a smaller number if it is single-brooded, some eagles, for instance, rearing only two young in a season. Naturally these few eggs must be very carefully protected. Since they are not laid in the yielding medium of water, they cannot have so soft a covering as the eggs of the fish or frog, but are enclosed in a hard sh.e.l.l. This sh.e.l.l must of course be formed before the egg is laid, and the egg must be fertilized before the hard sh.e.l.l encloses it and thus makes forever impossible the entrance of the fertilizing cell.
The ovaries of the bird are in the small of the back close to the backbone, and there is a tube called the oviduct or egg-duct, leading from the ovary down to the lower end of the intestine, which it enters.
There is no separate opening for the oviduct into the outer world.
There are two ovaries, with their oviducts, in the young bird, but these are so small that it is very difficult indeed to find them. As the bird approaches maturity, one ovary and its oviduct enlarge, and the ova, which develop from the inside of the ovary just as the ovule develops inside the flower ovary, also become large. Although the bird is born with two ovaries, but one, usually, develops, generally the one on the left side.
When the bird comes to maturity, there is born in it a yearning for home and offspring. As the eggs develop, the bird turns to the nest and to the mate who is to share with her all this beautiful life. When the mate has been chosen, both prepare the nest to receive the eggs, which will soon be ready. It is during this period that the fertilizing fluid is placed in the lower end of the egg-duct, whence the fertilizing cells, by their power of motion, quickly make their way to the egg, which has just begun its journey down the oviduct and is as yet without a sh.e.l.l.
The sh.e.l.l-less egg is well known to most country children, as hens often lay one; and this will always happen where there is not lime enough in the food of the poultry.
After the egg is fertilized it continues its slow journey down the oviduct, which enlarges to accommodate it. At first the egg consists of the yolk alone. This grows to its full size before it leaves the ovary.
The yolk in short _is_ the egg. But there is not enough food material in it for the development of the bird, so as it pa.s.ses down the egg-duct it becomes coated by the so-called "white" of the egg, which is a substance secreted from the lining of the egg-duct and is not alive, as is a certain part of the yolk. It is merely stored-up food like that in the morning-glory seed, for this egg is the seed of the bird. At the lower end of the egg-duct there is secreted a limy liquid which covers the sh.e.l.l-less egg and hardens, making the sh.e.l.l. So finally the fertilized egg has its sh.e.l.l and is ready to be laid. When this time comes, the bird seeks her nest, and the egg is laid or born, and lies warm and living, like a jewel in the nest.
It is hardly necessary to add that the fertilizing cells in the male bird have an origin similar to that of the ova. The t.e.s.t.i.c.l.es and their ducts are too small to be easily seen in the young bird and in the winter-time, but can be seen during reproductive activity. The male bird can usually be told from the female by differences in color and plumage, but where this is not the case the two s.e.xes cannot be told apart without actually killing and dissecting the birds, so very simple are the generative organs.
The ripening of the reproductive elements in the bird occurs in the spring of the year, and is always with a few exceptions accompanied by the instinct of nest-making. The birds instinctively and joyfully prepare the home for their young at this time, both parents joining to make the pretty structure. With the child the higher emotions which always accompany reproductive activity in the bird life should be kept ever prominent,--the affection between the parents, their care and love for each other, the care and love for the helpless young, their happiness in this duty as shown in their song and bright colors. Unlike the fish and the frog, the bird cannot develop unless the egg is kept warm, and after it hatches the young bird cannot take care of itself for several weeks. It must be carefully nurtured, and finally even taught how to fly and find its food.
The maternal hen can be a treasure to the mother seeking to impress the lesson of love and care; the only defect is the indifference of the father, which is in marked contrast to the interest shown by other birds, though there are many proofs that the c.o.c.k is not without parental love, as where young chicks have been abandoned he has been known to rear them.
The love of both the birds for their helpless young, and their devotion to each other, can be impressed on the young mind in many a picture of beauty. Many birds pair for life, returning to the same nest year after year. Nor should the instruction fail to impress upon the young mind the advance of love and tenderness on the parent for the offspring as we ascend the scale of life. The flowers, the fishes, the frogs, entrust their offspring to the care of Mother Nature; the birds cannot do this.
The mother and the father of the helpless little creatures take deep joy in sacrificing their own freedom and strength and time to this loving duty. A bird will even lose its life for its young, trying to drive off an enemy; and every one knows how dangerous it is to approach the nest of any large bird, eagles and even cranes sometimes killing men and boys who try to rob them of their young.
The plumage of birds is a pretty subject of study. The wonderful way in which feathers are adapted to their use, in keeping the bird warm without greatly increasing its weight or impeding its flight, may be made very interesting; also their beauty both of structure and color, and the fact that at maturity the plumage often undergoes remarkable changes. Young birds are colored like the mother. The brilliant male of the Baltimore oriole gets his bright dress at maturity, but until that time he is as soberly clad as his quiet little mother.
The inheritance of the young bird from its father should be enlarged upon. At the beginning, though the male birds resemble the mother in appearance, at maturity they wake up to the characteristics of their father. Then the brilliant colors begin to play over their feathers--his colors. Then the song trembles from their throats--his song; and the beautiful creatures might sing as their wonderful wings flash through the air, "All this loveliness I owe to my father: it is from him I received this glorious heritage of beauty and song."
The child can learn the terrible consequences to the birds of their feathers being taken as ornaments by human beings. The children can be told that the plumage is most beautiful at the mating and nesting season, and that thousands of birds, both male and female, are slain then, that the eggs and young birds consequently die, and that some species have been almost if not quite exterminated in this cruel way.
The Audubon societies are organized for the purpose of instructing young people about the birds and getting their cooperation in opposing this needless slaughter. Some of these organizations are extremely interesting in their field and lecture work on birds; every neighborhood could have its Audubon society, to the great pleasure and profit of the members as well as to the profit of the birds.
Where the mother desires to pa.s.s directly from the flower to the bird, this can be well done by comparing the two, so far as their generative processes are concerned, at every step. She can remind the little one of how the flower seed is treasured in the ovary until it is able to go out into the big world, and can then tell him that the wonderful seed of the bird, which we call the egg, is treasured in the same way; this to be followed by the story of the care needed by the bird"s egg after it is born,--how it cannot be left to shift for itself, but must be watched over and kept warm by its loving little parents until it is fit to leave the sh.e.l.l, how it then breaks its prison and comes forth so weak and helpless to be yet further loved and cared for and taught by its faithful parents.
The question is often asked, should not the story of motherhood precede that of fatherhood in all this early teaching? Up to a certain point it may be well, and the story of the life and development of the egg can be told to young children, with the father-bird merely an aesthetic factor, so to speak. His care of the young, and protection of the mother-bird can be dilated upon without going any farther. This is a course, however, which it will not be wise to follow too long, particularly with boys, whose interest will be greater when they know that the father too has a vital interest in the life of his offspring. Moreover, there is a certain spiritual value in connecting the equal need and responsibility of both parents in the creation of their offspring. The child then knows that he has the whole truth, and half truths are never quite safe.
If the child knows the story of flower, fish, and frog life, he will draw his own conclusions about the birds, and it will be wiser frankly to tell him this part of the story. If he knows nothing of the earlier work, and the mother begins with the young birds in the nest, according to his age and surroundings he should be told more or less, the mother always remembering that if she defers too long somebody may antic.i.p.ate her with the kind of information she particularly desires to avoid.
Another question often asked concerning the bird is, "Would the egg be laid if it were not fertilized?" It might be or it might not. In all forms of life the sensitive reproductive system responds with peculiar readiness to its environment. In birds if it does not receive the stimulus that comes from mating, the ova may not develop at all, but remain small and attached to the ovary. Or, a few may be completed and laid, as is often seen in the case of caged female canaries. But these eggs of course could never hatch. They are perfect so far as the ovum is concerned, but lacking fertilization they cannot continue their development.
Another question often asked, and of peculiar meaning, is, "If the reproductive system be not exercised, will it not perish for lack of exercise?" The latest word of science on this subject is that it will not, either in the bird or elsewhere. In a healthy organism it can safely remain inoperative with the certainty of becoming active at a later period if then it receive the normal stimulus.
The lessons to be learned from the birds are many. From them can be answered all questions, for now we have pa.s.sed that most difficult of all points, the relation of father to child in the animal world, and everything else can be explained through the knowledge already gained.
The well-taught child will recognize the justice and necessity for the existing processes of life. He will realize their deep meaning, their far-reaching influence, and their tremendous importance in preserving upon the earth the mult.i.tudes of living forms that inhabit it.
The flower and the bird are the two most important helps in imparting the facts concerning the renewal of life throughout nature.
XI
THE MAMMAL
The mother who has conducted the child through the various life forms up to the mammal will not be likely to wish to stop there. Having gone thus far, it will be easy to continue and reveal to the child the wonderful life that yet remains.