Scientific realism generally accepts that theoretical terms refer to an observer-independent world and that scientific theories describe the causal structure of the world in a relatively straightforward way. Richard Dawkins' use of metaphor in The Selfish Gene and The Extended Phenotype in his descriptions of genes as replicators, as bearers of information, and as intentional systems raises questions about the nature of metaphor and about the metaphysical and epistemological status of the entities and processes invoked in evolutionary explanations. It is argued that traditional descriptions of metaphor are inadequate general accounts of metaphor. Metaphor should be understood in terms of the interaction of two implication-complexes that represent the world in much the same way as a map or picture. Dawkins' descriptions should be seen as metaphors, cognitive instruments that allow us to discriminate real patterns in the world. We extend these patterns in order to predict the behaviour of living things and to identify causal relationships. (Dissertation Abstracts)