  Three subjects are considered here: a self-dual non-critical string that
appears in Type IIB superstring theory at points in ${\rm K3}$ moduli space
where the Type IIA theory has extended gauge symmetry; a conformal field theory
singularity at such points which may signal quantum effects that persist even
at weak coupling; and the rich dynamics of the real world under
compactification, which may be relevant to some attempts to explain the
vanishing of the cosmological constant.
