Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
It is a common myth that an earthworm becomes two worms when cut in half. However, only a limited number of earthworm species are capable of anterior regeneration. When most earthworms are bisected, only the front half of the worm (where the mouth is located) can survive, while the other half dies. Also, species of the planaria family of flatworms actually do become two new planaria when bisected or split down the middle.