Bernard Marx can be considered a flat character. That means that he doesn't develop or change or "see the light" as he journey's through the story. He's the same person at the beginning as in the end. The reader, however, is introduced to different aspects of his character as he faces different events in the story. At first, he is in love with Lenina and remains a self-pitying fool until he goes to the reservation and meets John. The reader is then introduced to his manipulative side as he takes advantage of the Savage's situation to save his own skin at his job and to humiliate his boss. Ironically, he doesn't know that what his boss was going to suggest was exactly what he gets in the end--to be moved to an island where he can feel more comfortable with his existance. Bernard is intelligent and selfish just like the State made him to be, but we also see that when he is confronted with unknown informaion and uncomfortable circumstances he can also be a baby and a coward; but, the State never trained people like him to be anything else.
The link below sends you directly to more informatio about the chaacters; and, Marx is first on the list.