how does gene react to Leper's story of his experience?

One thing that Leper is able to do after his army experience is peg Gene's personality, and know what he did to Finny. Finally, naïve little Leper evaluates Gene in a more accurate way than anyone else in the book; "You always were a savage underneath," Leper tells Gene, "a swell guy, except when the chips were down" (136). The appraisal is absolutely right on, though Gene of course doesn't want to hear it. So Gene breaks out into violence, confirming Leper's statement. Gene says that he doesn't really care about Leper, and shows off his angry temperament quite a bit in this chapter. We see that Gene, for all his civility at school, still has a bit of a mean streak in him, and still has the capacity to lash out at people for nothing, like he did with Finny. Gene is unstable and unpredictable when faced with the truth, or with something that upsets him; he's not quite the nice rule-abider he wants to portray himself as, as he displays once again. This introduces the theme of appearance vs. reality, because as Gene refuses to understand his own nature, he will be unable to represent himself the way he really is.