The grey jelly is either frog's spawn or toad's spawn.
If it is just a lump with no particular shape to it, it is frog's spawn, but if it is made up of small slimy ropes, which come apart from one another, and in which the eggs lie in rows like strings of black beads, it is toad's spawn. When you find toad's spawn, you may be sure that frog's spawn has been about for some time, for frog's spawn is always to be found rather earlier in the year. Whichever it may be you should take a little of it (quite a little is best) and put it in a glass jam-jar half full of water, and stand this in some bright, warm place, where it will not get knocked over, and where the sun will not shine directly on to it.
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.
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.
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