In Chapter 4 of Lord of the Flies, why does Roger throw stones at Henry, and why doesn't he hit him?

Roger's throwing rocks at Henry seems merely like a boyish game at first. He is, after all, "throwing to miss" the child. The narrator tells us that Roger does not hit Henry because around him there circled a "taboo of the old life"--a life full of "parents and school and policemen and the law." These things have always kept Roger and the other boys in line. Roger, whose arm is "conditioned by a civilization that knew nothing of him and was in ruins," will not respect these taboos for much longer. He will become one of the most brutal members of Jack's tribe.