Abstract
Frequencies of the acrocentric homomorphic (A/A), the acrocentric and subtelocentric heteromorphic (A/S) and the subtelocentric homomorphic (S/S) types in the pair nos. 1 and 9 of the black rats are examined in 46 specimens collected in the Osaka-city of Japan. A considerably high frequency of the A/S and the S/S types observed in these specimens is rather similar to those distributed in the Kanto district of Japan. These features are explained by the historical migration events of the black rats.
