A. S. PARKES
Marshall Professor of the Physiology of Reproduction, University of Cambridge.
I am always very pleased to be able to visit the U.S., to meet old friends again and to make new ones. On this occasion it is also very nice to think that the new friends will largely be young people. In giving me the invitation, Dr. Greep said that the aim of this meeting would be to combine a small proportion of gray heads with a large one of young people. I thought this was a most excellent idea and I need hardly say that for that and other reasons I jumped at the invitation to be present. May I say that it is much more stimulating to be with people who may have a future, rather than with old ones who only have a past.
I gather from looking down the list of participants that I am the only one here from overseas; whether I was the only one invited, I don't know, but in any case, I appreciate the compliment. I would like very much to take this chance, therefore, of offering my very heartiest thanks to the organizers of this seminar, to the American Academy of Arts and Sciences and also to the Ford Foundation, for the fact that I am here.
MY THEME is the Biology of Fertility, which I take to mean the biology of fertility in mammals, and to include, of course, the control of fertility. I want to tackle this vast subject in a very