[A description of the B chromosomes in the karyotype of the field mouse Apodemus agrarius].

For the first time B-chromosomes were detected in Apodemus agrarius. In the mouse of the population from the Khabarovsk Territory. B-chromosome is a minichromosome and it is found in all metaphase plates (2 n = 48 + 1B). B-chromosome of the mouse from the Maritime Territory is a medium-sized heterochromatic acrocentric (2n = 48 + 0-1B) and it is found in 53% of metaphase plates analyzed.