Elie Metchnikoff (1845-1916), winner of the Nobel Prize in 1907 for his contributions to immunology, was first a comparative zoologist, who, working in the wake of Darwin's On the Origin of Species, made seminal contributions to evolutionary biology. His work in comparative embryology is best known in regard to the debates with Ernst Haeckel concerning animal genealogical relationships and the theoretical origins of metazoans. But independent of those polemics, Metchnikoff developed his phagocytosis theory' of immunity as a result of his early comparative embryology...