The author discusses the significance of the ≪species problem≫ in the context of evolutionary biology and of systematics. He concludes that, contrary to current tendencies, a strongly nominalistic concept of the ≪species≫ is the only tenable one, that species cannot be conceived as individuals and that the species concept is irrelevant for evolutionary biology. Moreover a careful analysis of the species concept falsifies some of the basic tenets of Hennigian and of transformed cladism.