What did Ralph do to the "Lord of the Flies"?

From the text:

Fiercely he hit out at the filthy thing in front of him that bobbed like a toy and came back, still grinning into his face, so that he lashed and cried out in loathing. Then he was licking his bruised knuckles and looking at the bare stick, while the skull lay in two pieces, its grin now six feet across. He wrenched the quivering stick from the crack and held it as a spear between him and the white pieces. Then he backed away, keeping his face to the skull that lay grinning at the sky.