In 1963 the director general of the 'Office de la Recherche Scientifique et Technique Outre-Mer' (ORSTOM) asked me to form a well structured team of hydrobiologists based at Fort-Lamy (now N'Djamena) where a laboratory could be built as a branch of the already existing ORSTOM Center. The International Biological Program, IBP, had at this time recommended an integrated study of ecosystems selected in proportion to their representation of a particular zone or ecological conditions. I took this opportunity to propose Lake Chad as the model of a tropicallake in a semi-arid c1imate as part of the...