In spite of its proximity to Africa (the distance between Cap Saint- Andre and the African coast is only 300 km. ) Madagascar cannot be considered as adependent part of that continent. The Great Island has been separated from Mrica from at least the middle of the Secondary, and has evolved separately: its flora and fauna have acquired a very pronounced individuality, in spite ofsome affinities with Africa (although they also have affinities with India and the Indian archipelago). No naturallaboratory could lend itselfbetter ifnot to all, at least to the majority, of the absorbing problems offered for study by the history and evolution of plant and animallife in Madagascar. The edirors have tried to ensure that each of these problems is presented by the foremost authority in his particular field. In the first section, the natural environment, the foundation of any biogeographical study, is analysed. Professor R. BATTISTINI, Director of the Laboratoire de Geographie of the Faculte des Lettres et Sciences humaines of Tananarive opens with a description of the relief and the mairi types of landscape found in Madagascar. Professor P. BRENON, who initiated the teaching of geology and founded the Laboratoire de Geologie of the Faculte des Sciences of Tananarive presents the result often years ofresearch on the geology ofMadagascar. The climate, an essential factor, preliminary to any biogeographical study, is examined in detail by G. DONQ. UE, Maitre-Assistant at the Laboratoire de Geo- graphie. Professor J.