Once, when I was a little girl, my brother and I brought home some very strange pets.  We had been for a walk with our parents and had seen some big rain puddles with little wriggling creatures inside.  My daddy said that they were tadpoles.  We got a jar and scooped up a bunch of water with little tadpoles in it and carried them back to our house.  Out in the back yard, my daddy dug a big hole and filled it with water from a hose.  Then he laid a wooden plank across the hole, and we put the tadpoles into their new home.  Every morning before school, my brother had to go out and fill the hole with water, so the tadpoles would have plenty of room to swim, and every afternoon when he got home we would stretch ourselves out on the plank and look into the water to see what our new pets were doing.  As the weeks went by, the tadpoles began to change.  First they grew little stumps on their bodies.  Then the stumps grew longer and longer until they looked like arms and legs.  Then their little tails started to shrink away.  Finally, one morning when we went outside, there were no more tadpoles in the water!  Where did they go?  How did we lose our pets?  And then we saw something else, lots of little somethings, a hundred of them, hopping unexpectedly up out of the grass.  Our tadpoles had completed their transformation and now our pets were frogs!