What is "macrostomum"

Macrostomum is a genus of Platyhelminthes with a worldwide distribution, with over a hundred species described to date. These hermaphroditic, free-living flatworms are usually small in size, with large species reaching up to 5 mm in body length (e.g. Macrostomum tuba). They are usually transparent, and the smaller species appear rather round in cross-section than dorsoventrally flattened.