  It is shown that the heterotic string emerges as a soliton in the type I
superstring theory in ten dimensions. The collective coordinates of the soliton
are described by a smooth, chiral worldsheet theory. There are eight bosonic
and eight right-moving fermionic zero modes that arise from the partially
broken supertranslations. In addition, there are 496 charged bosonic zero modes
of the gauge field that describe a left-moving WZNW model on a $spin(32)/{Z_2}$
group manifold. Small, stable loops of the solitonic string furnish the massive
states required by duality that transform as spinors of $spin(32)$.
