The word “Umwelt” is not translated as yet and can perhaps not be translated. In its orginal and well known sense, inaugurated byUexküll, it means of the relations of an organism to its surroundings only those going over the receptive organs and the effective organs, while vegetative relations to the medium,e.g. respiration are excluded. The “Umwelt”-conception of ecology has always been a wider one, but by feeling only, without definition. H.Weber has tried to develop a “general biological Umwelt-conception”, including a (...) 11 relations. In spite of this claim he states, the “Umwelt” of a species be only those external conditions which are indispensable for its life. Here is demonstrated that this conception is quite insufficient, especially because it does not contain so fundamentally important relations as the enemies of an organism and the reactions of the organism upon its surroundings. Furthermore, that conception of “Umwelt” does not contain external conditions determinating the phenotype but not indispensable for the life of the species. A “general biological conception of Umwelt”, asWeber claims to have created, is impossible; the conception is divided in steps corresponding to its application in different branches of science. In physiologye.g. only the direct relations of an organism come in question, in epidemiology the vital relations only. The ecological conception is the most comprehensive, containing all those parts of the surroundings to which an organism has direct or definite indirect relations, and is the complex of them. (shrink)