  In [GH], Griffiths and Harris asked whether a projective complex submanifold
of codimension two is determined by the moduli of its second fundamental forms.
More precisely, given a nonsingular subvariety $X^n \subset {\mathbb P}^{n+2}$,
the second fundamental form $II_{X,x}$ at a point $x \in X$ is a pencil of
quadrics on $T_x(X)$, defining a rational map $\mu^X$ from $X$ to a suitable
moduli space of pencils of quadrics on a complex vector space of dimension $n$.
The question raised by Griffiths and Harris was whether the image of $\mu^X$
determines $X$. We study this question when $X^n \subset {\mathbb P}^{n+2}$ is
a nonsingular intersection of two quadric hypersurfaces of dimension $n >4$. In
this case, the second fundamental form $II_{X,x}$ at a general point $x \in X$
is a nonsingular pencil of quadrics. Firstly, we prove that the moduli map
$\mu^X$ is dominant over the moduli of nonsingular pencils of quadrics. This
gives a negative answer to Griffiths-Harris's question. To remedy the
situation, we consider a refined version $\widetilde\mu^X$ of the moduli map
$\mu^X$, which takes into account the infinitesimal information of $\mu^X$. Our
main result is an affirmative answer in terms of the refined moduli map: we
prove that the image of $\widetilde\mu^X$ determines $X$, among nonsingular
intersections of two quadrics.
