Mysterious Earthworm Sex: Mom or Dad or Both ?

Mysterious Earthworm Sex: 

Mom or Dad or Both ?

An earthworm is bisexual. So when earthworms are mating, one is delivering and receiving sperm from another to fertilize an egg.

The surprising twist can be when young worm are talking to each other, "Your mom is my dad!"

Such phenomenon is not possible in human like animals.