Dr Yasunori Kano, of University of Tokyo, discovered jet-black egg capsules at a depth of 20,341 feet while piloting a remote-operate vehicle in northwestern Pacific's Kuril-Kamchatka Trench. Upon presenting them to Dr Keiichi Kakui of Hokkaido University, it was discovered they are are the cocoons of flatworms (platyhelminths). This study provides the deepest record for free-living flatworms.