Evolutionary Biology, of which this is the eighteenth volume, con­ tinues to offer its readers a wide range of original articles, reviews, and commentaries on evolution, in the bro~dest sense of that term. The topics of the reviews range from anthropology and behavior to molecular biology and systematics. In recent volumes, a broad spectrum of articles have appeared on such subjects as natural selection among replicating molecules in vitro, mate recognition and the reproductive behavior of Drosophila, molecular systematics ofCrocodilia, evolution of the monocotyledons, and the com­ munication network made possible among even distantly related genera of bacteria by plasmids and other transposable elements. Articles such