It started as a joke. The substitute was in for a teacher who taught the odd combination of history and sciences. The teacher’s history class, knowing there was a substitute, informed her of the “fact” that they were a science class, not a history class. The substitute looked at the schedule, but the class informed her that there was a mistake and assured her that she should be teaching sciences. The substitute could find no plans, so she told them about a book she had been reading that spoke about Gregor Mendel, who had discovered the rules of heredity. She drew diagrams on the blackboard and spoke with enthusiasm about the wonder of heredity as it had unfolded to her. The class, who thought that they had pulled off a fine joke, soon settled down and became fascinated by the obvious enthusiasm of this substitute teacher. One of the boys in that class was so impressed, in fact, that he went to the library to look up more about the subject. His interest grew. He graduated a...