The cercarias released from the snail into the water have a head and a Y-shaped tail. Then, encountering humans, individual cercaria attach and release proteolytic enzymes that enable the cercaria to penetrate human skin. The cercaria’s tail is lost. Now known as a schistosomulum, it penetrates the skin and passes to the lungs. From the lung, by mechanisms that areunknown, the schistosomulum passes to the host’s liver, where it matures in the portal circulation to an adult schistosome. Adult worms then migrate to specific venous plexuses, where they produce eggs that are either: a) excreted to repeat the cycle or b) pass in the venous system to other organs.