2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/102205We derive explicit formulas for the action of the Hecke operator $T(p)$ on the genus theta series of a positive definite integral quadratic form and prove a theorem on the generation of spaces of Eisenstein series by genus theta series. We also discuss connections of our results with Kudla's matching principle for theta integrals.23 pages, to appear in the proceedings of the conference to the memory of Tsuneo Arakawa, Tokyo 2004. Revised Dec 14,2005: typos removed, some formulations correctedNumber Theory11F46text