"Initially we were puzzled why every worm was a female," Vrijenhoek said in a telephone interview. He said Rouse took some worms to his laboratory for study and discovered tiny male worms living inside the females.
There were as many as 50 to 100 males within each female, Vrijenhoek said.
The males still contained bits of yolk, as if they had never developed past their larval stage, but they also contained large amounts of sperm. [CNN.com]