Devoted mainly to the geography of Lakes Rudolf and Baringo in Kenya and Lakes Edward and George in Uganda. They have been sounded for the first time, parts have been surveyed and mapped, and preliminary biological surveys have been completed. A section is devoted to distribution and history of the fauna, especially fish. There are 2 types of aquatic fauna in the Nile system: (1) that of Albert, Rudolf and the Lower Nile, characterised by the genera Lates, Hydrocyon, Citherinus, etc.; (2) that of Victoria, Kioga, Edward and George, where these genera are absent but where there are many endemic kinds of Cichlidae. The Murchison Falls on the Victoria Nile isolate Victoria and Kioga, and the Semliki Falls isolate Edward and George. Evidently the fauna of Edward and George was exterminated during the interpluvial (Pleistocene) arid period when these lakes were dried out. The same probably applies to Victoria and Kioga. Since the lakes refilled, the quickly evolving Cichlidae have peopled each with endemic forms. Geological evidence is summoned in favor of this view, and its explains the remarkable distribution of Crocodiles. A last section deals with the exploitation of fisheries, partly by using indigenous species and partly by introducing other fish. In a table all the lakes of Kenya and Uganda are compared with reference to area, depth, temp., alkalinity and pH.