This volume discusses recent advances in research regarding the evolution of specific and nonspecific defense responses in a taxonomically diverse array of species. Topics regarding invertebrates include the protective mechanisms (cellular and molecular) employed by insects, the protective roles of lectins, and the self-nonself discrimination revealed by tissue incompatibility reactions. With vertebrates, the evolution of the immunoglobulin-related superfamily of recognition molecules (including immunoglobulins and the major histocompatibility complex molecules) is examined over several...