Ontology without Axioms.- Le?niewskis Analysis of Russells Paradox.- Logic and Existence.- Le?niewskis Calculus of Names.- On Le?niewskis Ontology.- Ontology: Lesniewskis Logical Language.- On Le?niewskis Elementary Ontology.- Studies in Le?niewskis Mereology.- On the Definition of Mereological Class.- Consistency of Le?niewskis Mereology.- The Dependence of a Mereological Axiom.- Relation of Le?niewskis Mereology to Boolean Algebra.- Index of Names.