The relationship between the works of Marie de France and ancient and medieval literary influences has been well documented in the critical literature. Few critics, however, have addressed the importance of nature, and specifically animal imagery, in the Lais. The twelfth century witnessed, in all realms of human intelligence and endeavor, an unprecedented effort to systematize knowledge and rationalize human experience. Animal imagery, a traditional form of representation, was prevalent in diverse treatments in the Bible, in the works of the ancients, in Ovid, and in the matiere de Bretagne that was so much in vogue during the time of Marie de France The present investigation proposes a critical analysis of the role of animal imagery in six lays. Depiction of animals varies throughout the lays, but one constant unites the images: they are all presented in a state of metamorphosis, either physical or profoundly symbolic transformation. Metamorphosis is intimately associated with metaphor, which is intrinsic to thought and generative of language and literature, therefore the metamorphic animal characters can be interpreted metaphorically on generic, textual and socio-cultural levels Because genre is by nature both representational and transformational, the textual metamorphic animal images are validated by Marie's choice of the lay, a flexible and evolving narrative form, as a basis for her artistic recreation of the oral Bretannic tales. Choices made by the author from the available literary, social, political and cultural paradigms of her era produce new metaphorical readings along the syntagmatic axis of metamorphic animal imagery. This transformative process becomes a literary metaphor for the medieval compositional theory of translatio studii plus inventio The dependence of metaphor upon the receiver makes the Lais especially open to re-creation, indeed co-creation, through the glosses of succeeding generations of readers who interpret the metaphors of metamorphic animal imagery in light of their own paradigmatic experience. The animal images reveal metamorphosis to be the governing metaphor of the lays