  Abelian varieties of dimension 2n on which a definite quaternion algebra acts
are parametrized by symmetrical domains of dimension n(n-1)/2. Such abelian
varieties have primitive Hodge classes in the middle dimensional cohomology
group. In general, it is not clear that these are cycle classes. In this paper
we show that a particular 6-dimensional family of such 8-folds are Prym
varieties and we use the method of C. Schoen to show that all Hodge classes on
the general abelian variety in this family are algebraic. We also consider
Hodge classes on certain 5-dimensional subfamilies and relate these to the
Hodge conjecture for abelian 4-folds.
