taken for the most part from Petrarch, is obviously crucial to the agonistic nature of the work.' It is largely composed of a long series of examples which illustrate the Heraclitean principle Omnia secundum litem fiunt, "todas las cosas ser criadas a manera de contienda o batalla."2 Although there is an atmosphere of struggle and contention throughout the tragicomedy, how the examples in the Prologue relate to the work as a whole is not immediately apparent. Alan Deyermond, for example, thinks that Rojas would have done better to ignore the echeneis or rdmora, the small fish which can halt the movement of a large ship." What does such a case illustrate in regard to the story of Calisto and Melibea ?