In this paper we study the geometry behind an algebraic construction of LODAY known as Leibniz homology, HL,, [8] [9]. These homology groups provide a noncommutative setting for Lie algebra homology much like cyclic homology is a noncommutative setting for de Rham cohomology. For an algebra A over Q, CUVIER [3] and LODAY [8] have shown that HL,(gI(A)) is rationally isomorphic to a tensor algebra involving the Hochschild homology groups of A. To put this result in perspective, recall that LODAY and QUILLEN [lo] have shown that H,(gI(A)), the Lie algebra homology of gI(A), is isomorphic to the graded exterior algebra A ( H C , -(A)), where H C , denotes cyclic homology. The calculation of HL,(gI(A)) is a lifting of the Lie algebra homology calculation to a certain tensor algebra. For a connected space X , it is also known [6] that the singular homology of QZX is isomorphic to a tensor algebra on the reduced homology of X . Here s2 denotes the based loop space and C is the reduced suspension. The tensor algebra in both cases can be explained in terms of certain presimplicial structures on the underlying space or chain complex. When A is the group ring Q [ G ] for a discrete group G, we establish an isomorphism between HL,(gI(A)) and the singular homology of a certain space involving the loops suspension functor and BG, (2.14). Here BG denotes the classifying space of G. Furthermore, we recover the James model [6] on BG in terms of various presimplicial layers suggested by the calculation of HL,(gI(Q[G])). The relation between the James model and Leibniz homology is the main geometric idea of this paper.Through an application of invariant theory to the chain complex defining Leibniz homology [8], the symmetric groups appear early in this paper. We define a certain multi-presimplicial stratification of these groups in which the m-presimplicial elements are precisely those permutations which can be expressed as the product of m-many disjoint cycles. This algebraic construction allows us to give an alternate proof of the computation of HL,(gI(A)). When this stratification is shifted slightly in dimension, the result is a chain complex for QCBG which is valid even over the integers.