27 August] 1864 – 25 July 1944) was a Baltic German biologist who worked in the fields of muscular physiology and animal behaviour studies and was an influence on the cybernetics of life.

[citation needed] However, his most notable contribution is the notion of Umwelt, used by semiotician Thomas Sebeok and philosopher Martin Heidegger.

He argued that organisms experience life in terms of species-specific, spatio-temporal, "self-in-world" subjective reference frames that he called Umwelt (translated as surrounding-world,[6] phenomenal world,[7] self-world,[7] environment[8] - lit.

Because all organisms perceive and react to sensory data as signs, Uexküll argued that they were to be considered as living subjects.

The Umwelt is for him an environment-world which is (according to Giorgio Agamben), "constituted by a more or less broad series of elements [called] "carriers of significance" or "marks" which are the only things that interest the animal".

Agamben goes on to paraphrase one example from Uexküll's discussion of a tick, saying, "...this eyeless animal finds the way to her watchpoint [at the top of a tall blade of grass] with the help of only its skin's general sensitivity to light.

The odor of butyric acid, which emanates from the sebaceous follicles of all mammals, works on the tick as a signal that causes her to abandon her post (on top of the blade of grass/bush) and fall blindly downward toward her prey.

He argues every organism has an outer boundary which defines an Umwelt (German word generally meaning "environment", "surrounding world").

He further distinguishes the Umgebung (that part of the Umwelt that represents distal features of the external world, in German "that which is being given as surroundings") from the Innenwelt which is reported directly by sensors and is therefore the only unmediated reality immediately knowable to the organism.

[14] However, despite his influence on the work of philosophers Max Scheler,[15] Ernst Cassirer, Martin Heidegger, Maurice Merleau-Ponty, Peter Wessel Zapffe, Humberto Maturana, Georges Canguilhem, Michel Foucault, Gilles Deleuze, Félix Guattari (in their A Thousand Plateaus, for example) and José Ortega y Gasset he is still not widely known, and his books are mostly out of print in German and in English.

As late as 1933 Uexküll held hopes that the rise of Hitler to power might bring an end to the expansion of communism and the democratization of German society, for which he had an aristocratic antipathy, but his expectations were met with disappointment.

In May of the same year Uexküll wrote a letter to Eva Wagner Chamberlain, daughter of Richard Wagner, and wife of his late friend Houston Stewart Chamberlain, lamenting that the ideas of her husband were being used by Nazism to justify the persecution of Jews in Germany, and describing racial discrimination against Jews as "the worst kind of barbarism".

By the autumn of 1933, Uexküll evinced disapproval of Nazi policy and ideology, and afterwards tried to avoid political issues, although it sometimes proved impossible.

In 1934, Uexküll dedicated his book A Foray into the Worlds of Animals and Humans to a Jewish fellow researcher Otto Cohnheim, who, in his words, "lost his appointment as a university professor because of racial politics".

For example, Carlos Brentari [20] refers to Uexkülls autobiographical book of personal reminiscences, Nie geschaute Welten (Worlds never seen).

As Sprenger writes: "This rhetoric already holds the germ of the idea that the host must rid itself of this parasite, despite all sympathies he may harbor for individual members of the alien race, and thus end the supposed abuse of his hospitality.