Cells; the basic immunodefense armentarium - immunocytes of protostomes and deuterostomes as revealed by LM, EM and other methods; mechanism of antigen processing in invertebrates; cell products - natural and induced as revealed by nonspecific and specific responses following antigen change - the prophenoloxidase system; a definition of humoral lytic responses in invertebrates; the immunoglobulin superfamily; insect hemolymph proteins from the Ig superfamily; the interface between invertebrates and vertebrates. (Part contents).