The growth of new segments (body parts) in marine worms is controlled by a special growth zone, in which special stem cells are located. New segments then emerge by the division of these cells.

In a rare medical case, parasitic worms grew underneath a woman's upper eyelid.

The growth of new segments (body parts) in marine worms is controlled by a special growth zone, in which special stem cells are located. New segments then emerge by the division of these cells.

Freshwater worm eggs enter human hosts through the skin and circulate throughout the body, damaging multiple organs, ...

The cells that turn into sperm and eggs make up more than half its body. "It's basically a gut and two gonads," McNally said. But the little worm also shares some surprising affinities with us.