抄録
1. Lethal chromosome frequencies, the allelic rates of lethal genes and homozygous viabilities of quasi-normal chromosomes were estimated in the second chromosomes extracted from four natural populations of D. melanogaster distributed in the western and central parts of Japan.
2. The combined frequencies of lethal and semi-lethal chromosomes in each population were 15.1, 15.7, 7.3 and 20.1 per cent respectively. The mean viabilities of quasi-normal chromosomes in three populations were about 32 per cent. The allelic rates within population in the three populations were 5.3, 4.1 and 7.0 per cent respectively. Based upon these data, the Japanese natural populations were regarded to besmall in their sizes.
