  When eight-dimensional instantons, satisfying F \wedge F = \pm \star_8
(F\wedge F), shrink to zero size, we find stringy objects in higher order
ten-dimensional Yang-Mills (viewed as a low-energy limit of open string
theory). The associated F^4 action is a combination of two independent parts
having a single-trace and a double-trace structure. As a result we get a
D-string from the single-trace term and a fundamental string from the
double-trace. The latter has (8,0) supersymmetry on the worldsheet and
couplings to the background gauge fields of a heterotic string. A correlation
between the conformal factor of the instanton and the tachyon field is
conjectured.
