Geometric topology may roughly be described as the branch of the
topology of manifolds which deals with questions of the existence of
homeomorphisms. Only in fairly recent years has this sort of topology
achieved a sufficiently high development to be given a name, but its
beginnings are easy to identify. The first classic result was the
SchOnflies theorem (1910), which asserts that every 1-sphere in the
plane is the boundary of a 2-cell. In the next few decades, the most
notable affirmative results were the "Schonflies theorem" for polyhedral
2-spheres in space, proved by J. W. Alexander [Ad, and the
triangulation theorem for 2-manifolds, proved by T. Rad6 [Rd. But the
most striking results of the 1920s were negative. In 1921 Louis Antoine
[A ] published an extraordinary paper in which he 4 showed that a
variety of plausible conjectures in the topology of 3-space were false.
Thus, a (topological) Cantor set in 3-space need not have a simply
connected complement; therefore a Cantor set can be imbedded in 3-space
in at least two essentially different ways; a topological 2-sphere in
3-space need not be the boundary of a 3-cell; given two disjoint
2-spheres in 3-space, there is not necessarily any third 2-sphere which
separates them from one another in 3-space; and so on and on. The
well-known "horned sphere" of Alexander [A ] appeared soon thereafter.