  We show that each rigid symmetry of a D-string action is contained in a
family of infinitely many symmetries. In particular, kappa-invariant D-string
actions have infinitely many supersymmetries. The result is not restricted to
standard D-string actions, but holds for any two-dimensional action depending
on an abelian world-sheet gauge field only via the field strength. It applies
thus also to manifestly $SL(2,Z)$ covariant D-string actions. Furthermore, it
extends analogously to $d$-dimensional actions with $(d-1)$-form gauge
potentials, such as brane actions with dynamical tension.
