My understanding is that if hydra is cut into pieces, each piece can evolve into a new hydra. What I'm looking for is whether there exists an organism with a this property reversed, that is, if two or more such organisms meet, they would form new organism with the same property.
UPDATE: I do not mean the mythical creature, but this one. I should also have stated that I'm (obviously) not a biologist, so my terminology and information about the Hydra genus might be wrong. Despite that, I hope the question is still valid.