Borkin L. J. RussiaSt. PetersburgZoological Institute, Russian Academy of Sciences, 1 Universitetskaya nab., St. Petersburg 199034, Russialacerta@zin.ru Author's articles DISTRIBUTION OF THE «EASTERN» AND «WESTERN» FORMS OF THE MARSH FROG, PELOPHYLAX RIDIBUNDUS, AND THEIR PARTICIPATION IN THE ORIGIN OF HEMICLONAL HYBRIDS, P. ESCULENTUS IN MARI EL REPUBLIC