I AM greatly indebted to the Borden Award Selection Committee for inviting me here today. I am also grateful for the opportunity to acknowledge another debt, the one that I owe to Dr. L. Emmett Holt. Last night was passed pleasantly in the company of several old friends. As has become common on such evenings, our talk turned to Dr. Holt, because all of us there felt that he had exerted a strong influence on the course of our lives. It was Dr. Holt that made it possible for me to enter the field of research, and then provided me with an example of a teacher who is not above being taught, of an inquirer who doesn't resent being questioned, of a tireless worker capable of concentrated effort but with broad interests. Pleasant as these reminiscences are, I realize that I have been invited here to talk about the placenta, and that is what I intend to do. An occasion such as this offers the speaker the opportunity of summarizing experiences and concepts that have developed over an extended period of preoccupation with a subject. This is particularly pleasurable if one can discern a continuity that spans the years and provides a unifying theme for the countless details and apparently isolated observations involved in research. Now that teleology is becoming more respectable it is no longer quite as improper to seek to interpret experimental results in terms of a harmonious design obeying a logic of selection for survival. It is in that context that I would like to review the results of some of our studies of placental function.