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 chapters. Other topics reviewed include the evolution of nonimmunoglobulin mediators of defense (e.g., cytokines and eicosanoids), lymphocyte subpopulations (including effects of ambient temperature on function) and the phylogenetic emergence of natural killer cells. Phylogenesis of Immune Functions provides invaluable information for evolutionary biologists, as well as all immunologists and other researchers interested in discovering how inhabitants in our increasingly threatened biosphere protect themselves against environmental pathogens and toxins.