  The heterotic and type II superstring actions are identified in different
anomaly-free decompositions of a single topological sigma-model action
depending on bosonic and fermionic coordinates, $X^\mu$ and $\r^A$
respectively, and of their topological ghosts. This model results from
gauge-fixing the topological gauge symmetry $\delta X^\mu = \epsilon^\mu
(z,\bar z)$ ($\mu =1,2,\dots, 10$) and $\delta \r^\alpha= \epsilon^\alpha
(z,\bar z)$. ($\alpha=1,2.\dots, 16$). From another viewpoint the heterotic and
type II superstring actions emerge as two different gauge-fixings of the same
closed two-form. Comments are also made concerning the possibility of relating
$\rho^\alpha$ to a Majorana-Weyl space-time spinor superpartner of $X^\mu$.
