Litvinchuk S. N. RussiaSt. PetersburgInstitute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky pr., St. Petersburg 194064, Russiaslitvinchuk@yahoo.com 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