This article was originally a paper read at the 19th Psycho-Analytical Congress, Geneva, 24-8 July 1955. It was first published in the International Journal of Psycho-Analysis, 37:360-6. It was reprinted in The Collected Papers of Roger Money-Kyrle, 1978, ed. Donald Meltzer with the assistance of Edna O’Shaughnessy, Strathtay, Perthshire: Clunie Press.