The original essay in English on the concept of autopoiesis – introduced as a criterion by which to distinguish living from non-living systems – is “Autopoiesis: the organization of living systems, its characterization and a model” (Varela et al. 1974).359 The authors published that essay in the fifth volume of BioSystems; Margulis published an essay in BioSystems’ sixth volume (Margulis 1974a). As it happens, then, the concept of autopoiesis was introduced into Anglophone science in a journal that Margulis attended to, published in, and then co-edited, from 1983 to 1993. In December 1985, Margulis dilated on this topic in a letter marked under the date as “en route Pittsburgh–Boston.” Perhaps, as with Letter 77 a decade earlier, she was writing Letter 169 while on or waiting for a flight home. It appears to record Margulis’s impromptu responses to draft portions of a Lovelock manuscript. It also documents the intensity with which she took up the issue of autopoiesis at this stage of her theoretical engagement with Gaia theory. Lovelock did not reciprocate her enthusiasm in this regard.360