After this professorship at [the University of] Minnesota, three years later I had another invitation, this time from the University of Washington in Seattle in the north-west and this was particularly interesting. I was to give a course on evolution and simultaneously another visiting professor was invited, Richard Goldschmidt, a famous German biologist who had been driven out by the Nazis and who was opposed to Darwinian evolution. And I lectured on Monday, Wednesday and Friday, he lectured on Tuesday and Thursday at the same time, and in the front row were the full professors, behind them the associate and assistant professors, and behind them, in the auditorium, the PhD candidates and post-docs and finally the graduate students and finally the undergraduates. Well, naturally he… Goldschmidt and I, we contradicted each other continuously and the professors and all the people really knowing something about the field were immensely amused at… in fact, that was the whole reason why they brought the two of us together at the same time. But the poor undergraduate students couldn't understand it at all: how can two people be distinguished visiting professors and contradict each other? It's quite clear one or the other must be wrong, so why do… why do they invite the one who is wrong? So… I don't think these students ever solved that puzzle and you might even go so far as to say there was a little truth in this question of the students.