When he wrote Mutual Aid. A Factor of Evolution (1902), darwinist scientist and anarchist thinker Peter Kropotkin endeavoured to demonstrate that mutual aid is by no means a less significant factor of evolution than competition - and actually may be the most significant. As a result, evolution couldn’t be reduced to the survival of the fittest in a malthusian setting. Nevertheless, if there is intraspecific mutual aid, what about interspecific mutual aid, as well as broad relations between organisms and their environment ? Kropotkin addressed those issues in a series of seven articles published between 1910 and 1919 in Nineteenth Century and After. He relied on a wide range of material, mostly Lamarckian, available at the time. The outlook on evolution shaped thereby is one in which natural selection is confined to an ancillary role, whereas the direct influence of environment on organisms’ structure, development et collective behaviour proves crucial, as french zoologist Jean-Baptiste Lamarck had showed. Those articles were published before the building of genetics patterns into Darwinism. As such, they stand at a turning point in the history of science, designing a shaky lamarcko-darwinian synthesis. Besides, they grant us a better understanding of Kropotkin’s thought, in view of the way nature definitely proceeds according to non-malthusian rules, and in view of the way natural mutual aid extends itself in human history. This is the reason why those previously untranslated articles make up a missing link between Mutual Aid first chapter on animals and chapter two, dealing with « savages ».