In "Lord of the Flies", describe how the characters of Simon, Ralph, Jack and Piggy change in the course of the novel.

None of these characters undergoes a dramatic change, except for Ralph.  For the most part, the boys' characters are set and the events on the island only enhance the most prominent aspects of their personalities.  Simon is a mystic and a thinker.  When we first see him, we see him just as one of the boys, but one with a medical problem (the seizures). When he emerges as a character, we see him as one who observes his environment quietly.  He changes somewhat when he comes to the full realization of the source of evil on the island immediately followed by the realization of what the "beast" on the mountain top really is.  Piggy is the one who thinks things out in a practical, logical manner.  This is shown as soon as he tells Ralph about the conch shell.  He also changes somewhat when he realizes that the source of evil on the island is all of them, but like Simon, he dies for this knowledge.  Jack is shown from the beginning to be one who likes being in charge and something of a bully.  He makes the choirboys march in their hot robes and shows no sympathy for Simon's seizure.  As the story progresses, these qualities simply expand.  His desire for power and his brutish character become stronger and more evident until he is the dicator on the island with blood on his hands.  Ralph begins the story as a carefree boy enjoying the freedom that comes with no parental or supervisor restrictions.  He develops maturity as he comes to understand the need for order and rules.  By the end of the story, he also has come to realize the source of the evil is within each person, including himself.  This knowledge ages him tremendously and he cries for the loss of innocense that all this knowledge brings him.