In 1822, E. Metchnikoff discovered phagocytosis while he was studying starfish larvae. The following year, while carrying out experiments on Daphnia (Crustacea), the same author demonstrated the scale of the phe- nomen in the defence of the organism. Finally, between 1891 and 1910, L. Cuenot was the first to reveal lymphoid organs, in crustaceans and in- sects; some of these organs playa role in both phagocytosis and inhaema- topoieses. With rare exceptions, research into defence reactions in invertebrates was meagre in quantity and sometimes meagre in quality from then until the mid-1960's....