This article addresses the conception of the environment (Umwelt) of the Estonian physiologist and biologist Jakob von Uexküll (1864–1944). Uexküll’s core idea is that the Umwelt of animals and humans is a species-specific subjective construction. Two basic dynamics co-operate in this process: the first is a transcendental elaboration of the stimuli from outside reality, which creates potential signs ready to be used for the animal’s behavioural needs; the second is the re-assignation (Hinausverlegung) of these signs to the outside world. Uexküll’s theory about the construction of the Umwelt can only be understood by acknowledging both aspects (the transcendental and the semiotic) and keeping them together. A criticism could therefore be made of those interpretations of Uexküll’s thought that view the species-specific Umwelt as the product of a passive perception process. Finally, two critical points in Uexküll’s theory will be focused on: the risk of “species-specific solipsism” and an inadequate consideration of two peculiarities of the human semiotic environment (its high intra-specific variability and its inclusiveness towards other species’ Umwelten)

Key words: species-specific umwelt, transcendental subject, endosemiotics, ethology, biosemiotics