This is a bit horrible... so if you're squeamish, look away NOW! Rather Good dot com has brought together the game we've all been clamouring for for SO DARN LONG now... the game that lets you evolve worms and maggots into other beasts.
You can drag and drop the beasts into the four corners of the screen - water, dirt, dirt and carcass respectively, and these will have different affects on the evolution. There are 16 different beasts to uncover.
Just the mouse for this.
maggots can be dropped into the bottom right corner to become worms.