Abstract
The chromosomes of the F1-hybrids between the weak race (Sapporo, n=31) and the strong race (Hirosaki and Niigata, both n=31) came under study. All the hybrids herein concerned are of male character in their external appearance and structure of gonads, due to complete sex-reversal of the genetic females.
The chromosome number was found to be 31 in both primary and secondary spermatocytes with certainty. The conjugation between the homologous mates, the formation of the equatorial plate and the arrangement of the chromosomes in the metaphase plate at the 1st and 2nd meiotic divisions were usual without showing a slight sign of irregularity. The chromosomes of the haploid group are round or oval in outline. So far as the present study is concerned, they vary in size very slightly, forming a well-graded series in diminution of size.
