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Published online by Cambridge University Press: 22 January 2016
It is well known that the fundamental group π 1(X) of an arcwise connected topological space X operates on the n-th homotopy group πn (X) of X as a group of automorphisms. In this paper I intend to construct geometrically a group 𝒰(X) of automorphisms of πn (X), for every integer n ≥ 1, which includes a normal subgroup isomorphic to π 1(X) so that the factor group of 𝒰(X) by π 1(X) is completely determined by some invariant Σ(X) of the space X. The complete analysis of the operation of the group on πn (X) is given in §3, §4, and §5,