After they had changed their skins a few times, they had two breathing-tubes apiece instead of one, and these two grew out near their heads. And their heads were much larger. At the tail-end of his body each Wiggler now had two leaf-like things with which he swam through the water. Because they used different breathing-tubes, those Wigglers who had moulted or cast their skins several times now floated in the water with their heads just below the surface and their tails down. When a Wiggler is old enough for this, he is called a Pupa, or half-grown one.