This book is of great interest in the field of comparative immunology, in the study of the phylogeny of Immune response.For the first time it is shown sea star T and B lymphocytes, phagocytes playing the role of macrophages, . It is shown also NK cells with natural and INDUCED cytotoxicity against vertebrate tumoral cells. At last the main point remains the discovery of an INVERTEBRATE PRIMITIVE ANTIBODY with 2 Ig sites: a sea star Igkappa antibody.