Frog's Spawn
The Little Curly Tails are beginning to Grow
Have you ever seen Cook make a jelly? The first thing she does is to soak the gelatine in water, so that it gets soft and swells to twice the size it was before. It swells because it takes up water inside it, and frog's spawn does just the same. Now we must try and think what the frog's spawn jelly is for. It is really the white of the eggs, the black beads being the yolk. You wouldn't understand all its uses, but one is that it makes the frog's spawn much more difficult to eat, because it is so slippery. A great many water birds are very fond of frog's spawn and would gobble it up very quickly if they had a good, big spoon, instead of a rather small bill. As it is, a great deal of frog's spawn and a good many tadpoles are eaten up one way or another, which is really rather lucky for us, for frogs and toads lay millions and millions of eggs, and, if they all hatched out, there wouldn't be room in the world for all little frogs and toads.
The Tadpoles are here seen Getting very like Frogs
Most of them have all four legs, but one has only his hind legs at present
Well, if you keep your glass bottle with the eggs in it in a good place and look at it every day, you will find something fresh to interest you every day. First the black yolks will grow larger and change their shape so that they seem longer than they are broad, and presently you will find that they are turning into tadpoles. The baby tadpole seems much too fat to begin with, and sticks out in front like a little alderman; but soon he gets slimmer again, and you find that he is growing a curly tail (which no alderman ever did), and that there are tiny markings where his eyes and mouth are going to be. He is still very small (about a quarter of an inch long), but before he is much bigger a very wonderful thing happens—it has been happening all the time, though you have not been able to see it—he grows a pair of gills like a fish. They are delicate, feathery things, and stand out on either side of his head, I should like to say "neck," but I do not think I ought to because frogs and toads have no necks at all, and so I suppose tadpoles have none either. All this time his tail is growing too, and presently it is long enough for him to swim with. When this happens he slips out of the jelly and wriggles about in the water. At present he has no real mouth, but he has a little opening, shaped like a horseshoe, near to where his mouth is going to be, and he uses this to hold on to weeds when he is tired, which he very soon is at first.
Once he is fairly hatched, however, his mouth grows quickly and he gets a pair of rather hard little jaws with which he can nibble the water-weed. When this happens you must, of course, put some water-weed into the bottle, though grass will do if you can't get anything else.
Tadpoles Full Grown
They are covered with little specks of gold. At the bottom one can be seen feeding
I told you that he had gills like a fish, but they are curious gills at this early stage because they have no flap of skin to protect them. If you want to see a fish's gills you must lift up the hard flap of skin which covers them. The tadpole soon grows a flap of skin, though, just like a fish, and this always appears first on the right side, so that at one stage he looks as if he had only one gill, the one on the left side. When both the flaps of skin have grown, the tadpole is really a little fish, and he stays in much the same shape, though he gets fatter and fatter, for about a month. At the end of this time he begins to grow legs, first the hind ones and then the front ones (newt-tadpoles grow the front ones first); but, in spite of his legs, he is still only a fish, because, instead of breathing the air with his lungs as a grown-up frog does, he breathes the water with his gills. During the next month, when he is getting on for three months old, another wonderful change comes over him. For a time he breathes both with his lungs (he has to put his head out of water for this) and with his gills, and so he is both a frog and a fish at once; but he gets more and more like a frog, and less and less like a fish. His lungs keep growing inside him, and his body and gills and tail get smaller and smaller, and his mouth and his eyes and his legs get larger and larger, and presently he leaves the water altogether, for he is tired of water-weeds and tired of his tail (he can swim beautifully without it), and he wants to make his meals off insects and slugs, and to learn how to croak and jump, and to be a great fat frog like Mother.
