There was this rather strict separation in American science at that time, between the university people and the museum people, and the museum people were always treated as the poor relations. But eventually people began to… give me some credit for my achievements and in due time I got an invitation to go to the University of Minnesota as a visiting professor. And I got… by that time [Frank] Chapman was retired, Murphy was chairman, and most of the material of the Whitney collection had been worked out, so I got this leave of absence… also they didn't have to pay for me during that time… leave of absence to go to Minnesota where a Professor Mennig, sort of, took care of me. Now I had never before given a course anywhere, and I hadn't done an awful lot of lecturing. And… however, I had in the meantime founded a… an evolutionary journal called Evolution and getting a… seen an awful lot of manuscripts of all the recent work on… in evolution, so I was sure I could produce a very interesting and very novel course on evolution because much of the material would be things that weren't even published yet. So, I made myself my notes and… and a series of folders to cover the various lectures that I was going to give and I gave my first lecture. And, of course, I wasn't familiar yet with all the tricks of a lecturer and after I'd talked for about 15 minutes I'd used up all my material in my first folder. And then I went to my second folder and I tried everything in the world to slow me… myself down and so… but I still used up the third folder even before that class was finished. And I was in total panic because I said to myself, ‘Where am I going to get the material to get all these lectures?’ There was still about 18 or 20, or whatnot, lectures to come. And I went to Professor Mennig and he laughed and he said, ‘Well, that seems to be happening to a lot of beginners’, and then he said, ‘Well, there're a lot of little rules that you have to learn. First of all, don't believe that if you said something once that the students have gotten it. You've got to say it two and three times, and that will use up some time’. And then he gave me a lot of other little hints. Then he said, ‘Now I have one last one’. He said, ‘Always have in your folder a tabulation with columns and… and lines and all that, and if you run out of material, you say to the class, well now this principle is best represented and illustrated by a tabulation which I will now put on the blackboard. Then by the time you make your lines and fill all the little squares and the class follows you and fills… you easily use up 10, 15 or 20 minutes and the class never notices that you are just wasting their time’. So, I had to use that only once, but that was my first experience of teaching.