(Wired) There's one creature that doesn't need to get hung up on retirement or deadlines, and accordingly it could well be immortal. This is the bizarre existence of the hydra, a half-inch tube of jelly that inhabits fresh water all over the world, where it lives a long, long time under the right conditions—and if you don't assault it.
Yet even then, it has remarkable powers of regeneration. Cut it in half and you'll eventually end up with two hydra. Mix a bunch of them up in a test tube, break them all apart into single cells, and still they'll re-form into a ball and split off as individuals. Yeah, I know, that doesn't really seem possible. But stick with me here.