Frogs and toads usually lay their eggs in places where the sun _does_ shine on them and warms them gently, and so hatches them out, but of course they do not lay them in glass bottles, and if the sun shines on these, the water will get warmer than is good for them, partly because there is no other water round to keep it cool, and partly because the bottle acts as a kind of burning-glass, and brings too much of the sunshine into itself, and so gives too much warmth to the eggs. Some people think the jelly of frog's or toad's spawn acts like a burning-glass too; this, however, is a burning-glass which Mother Nature has arranged, and so there is no fear of its not acting properly. [Illustration: THIS IS FROG'S SPAWN WHEN IT IS QUITE FRESH] If you find frog's or toad's spawn soon after it is laid, you will see only a small quantity of jelly round it, but this soon swells out and gets much bigger. [Illustration: THIS IS FROG'S SPAWN, TOO But I have photographed it with a microscope, so that you may see it a little bigger than it really is. Right in the middle is a Tadpole who has grown his feathery gills, and close to him is one like a little alderman. There is another Tadpole with gills towards the right hand bottom corner, but there is an egg behind which makes his shape wrong. All the round things are eggs and the long things are Tadpoles which have just hatched] [Illustration: 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. [Illustration: 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]