This is the scene when Roger is sitting and throwing Rocks at the littluns testing how far he can push what little restraints civilization still holds on him.
"We don't need the conch anymore, and we know who should say things."
This is the scene where they kill and do terrible things to the sow. As they are on the island their standards of what is ok devolves further and further into savagery.
After the death of Simon, Piggy says, "We was on the outside. We never done nothing, we never seen nothing."
Jack's tribe attack Ralph's group in order to steal Piggy's glasses. At this point civilization has broken down and they are at war.
"The rock struck Piggy a glancing blow from chin to knee' the conch exploded into a thousand white fragment and ceased to exist." The last semblance of civilization is gone and savagery is all that remains.