The Renewal of Life; How and When to Tell the Story to the Young

by Margaret Warner Morley

The adaptation of the fish to its surroundings is interesting. Not only is its form the very best for moving quickly through the water, but its covering is peculiarly appropriate, many fishes having a hard, protecting coat of shining scales. These scales, besides being beautiful and useful, are interesting in another way, for we know that they are only modified hairs, growing from the skin as hairs grow but having their form and size developed in special ways to serve their purpose. Scales and feathers are only another form of hairs.

Many interesting stories of fishes can be told or read to the children, and among other things they can learn about the swim-bladder, the large, strong air-sac, which can be compressed or distended at pleasure, making the fish lighter or heavier and enabling it to rise to the surface of the water or sink to the bottom. In Nova Scotia, where many codfishes are caught, the swim-bladders are called sounds, and are cooked as a delicacy.

In the spring of the year we eat the roe of fish, which is nothing more nor less than fish eggs. Wherever shad are used, the children will be familiar with the shad roe; and in the South mullet roes are universally used. The people there dry them in the sun, and the children particularly are very fond of them. The Russian caviare is the eggs of a species of fish, and is considered a great delicacy by some people.

Where do these eggs come from? The fish market or the kitchen on fish day will answer the question. The child who is privileged to pass part of the summer at the seashore where fishermen ply their trade will have ample opportunity to know, as will the child who goes fishing in any brook or pond and is allowed (as he always should be) to clean and cook the fish he has caught. Also the smelts, which are cooked whole, only the intestines being removed through a hole near the gills, will answer the question.

The Ovary of a Fish

The eggs of the fish are contained in a sort of double pouch or sac, shaped something like an old-fashioned silk purse. These sacs open into the intestine near its exit. They are the ovaries of the fish. From the inside of each ovary the tiny eggs, or ova, grow, just as the ovules grow in the plant ovary or seed-pod. At first they are a part of the ovary; later they grow larger and fall loose, until the ovary is filled with them. The ovary is always inside the fish. It is there when the fish is born, and even then there are the tiniest hints of ova in it. But the ova do not grow large until the fish is mature; they wait until the fish has developed its strength, its bone, and muscle. Then in the springtime they grow rapidly. They grow until they are ripe, when they lie free in the ovary; and others grow and are freed in the same way until the ovary, which has also enlarged to accommodate them, is quite full. The female fish is larger than the male, and looks plump and rounded at this season. In course of time the eggs thus developed will be shed—or born—whether they are fertilized or not. But, if they are not fertilized, no further growth will take place in them, and they will soon perish.

The child, knowing about the fertilization of flowers, can easily be led to see that the fish ova, like the flower ovules, cannot develop without pollen. The anthers containing the pollen are found in the male fish, and look like the ovaries, only they are not so large and their contents are not so firm. They seem filled with a formless substance instead of with little globular eggs. Under the microscope this formless substance is seen to be made of a semi-fluid material in which are held millions of pollen grains! Only we no longer call them pollen grains. We may call them fertilizing cells if we please, though there are several names for them. But they are essentially the same as pollen. They grow, in the same way, from the inside of the anther (which may now be called the testicle) and become free when ripe. The pollen grains cannot move of themselves; the fertilizing cells can. Each fertilizing cell is like an ovum, excepting that it is not so spherical and is lengthened into a sort of lash by which it can propel itself through the water. When the ova are laid by one fish, the other swims over them and the fertilizing fluid is expelled into the water just as the eggs were. There is no union whatever between the parents for the purpose of fertilization. As soon as a fertilizing cell comes in contact with an ovum it seeks to enter into its substance, and as soon as this has happened, the two cells thus united begin to develop into a very tiny fish. As soon as the change begins, we have the embryo of the fish, which thus corresponds to the embryo of the seed.

There is one great difference between the ovary of the plant and that of the fish. When the plant ovary is ripe, its seeds are shed, and then the ovary itself falls off. The plant ovary thus bears only one set of seeds. In the fish, the ovary always remains in the fish, and after the eggs are shed, it shrinks up to a very small size, and remains so until it again develops and becomes distended with more eggs the following season. The same is true of the fish's testicles. When the time comes, the fertilizing material is expelled. After this the sac shrinks up to small size until the following season.

When the embryo has grown to its perfect form, the egg-shell is broken and out swims the young fish. When it leaves the shell we say it hatches, just as we say the plant embryo sprouts when it leaves the egg-shell or seed-shell. Like the pollen of the flower, the fertilizing cells of the fish cannot act upon any ova but those of its own species.