ON DISTRIBUTION OF 2 MICROTUS-ARVALIS CHR OMOSOMAL FORMS IN EUROPEAN RUSSIA

Data on the occurrence of two Microtus arvalis karyotypic forms (''arv alis'' and ''obscurus'') in Nizhnii Novgorod and Vladimir districts ar e represented.,Only one form, ''obscurus'', was found in Nizhnii Novgo rod district and both forms were collected in adjacent Vladimir distri ct on the right bank of the Klyazma river. The minimum distance betwee n sites of the found forms was 24 km. No contact zone was revealed in spite of the absence of geographical barriers within the gap.