This paper represents a revised and expanded version of a lecture that I gave in Cologne in April 2010, under the auspices of the Internationales Kolleg Morphomata. I am grateful to the Directors of the Kolleg, Günter Blamberger and Dietrich Boschung, for the invitation to be among the first Morphomata Fellows and to present my research as part of a Ringvorlesung. I also thank Frank Wascheck and Thierry Greub for their help in preparing the manuscript for publication.—Earlier versions of the paper were delivered at the University of Sydney in 2008 and the University of Wisconsin at Madison in 2009. A brief version of the paper printed here was given at the American School of Classical Studies at Athens in June, 2011, as part of a conference in honor of Susan I. Rotroff. It is to her that I would like to offer this book, as a token of many years of friendship and inspiration
