As introduced by Eilenberg and
Schützenberger, a pseudovariety is a class of finite algebras closed under the
formation of homomorphic images, subalgebras and direct products of finitely many
algebras. Many previous results about the lattice of varieties of inverse semigroups
are found to have analogues for the lattice of pseudovarieties of (finite) inverse
semigroups. In particular, certain intervals are modular, including the interval
consisting of the pseudovarieties of groups.