This fourth volume of Contemporary Topics In Immunobiology treats in vertebrate immunity. Specifically, the results represent several approaches to humoral and cellular immunity. It is evident that invertebrates do have function ing immune systems. For example, cellular immunity is characterized by both specificity and memory, but it is still problematical whether vertebrate immune capacity evolved directly from invertebrates. Most of the manuscripts were formally presented at the International Symposium on Invertebrate Pathology, University of Minnesota, August 1972, held in connection with...