Twenty-two young adult C3H/He male mice were exposed to 3Gy, preferable condition to induce myeloid leukemias, and another group of 22 males to the fractionated irradiation of 4×1.7Gy, preferable to lymphoid tumors. The stable type aberrations of chromosomes in bone marrow cells of those mice were analyzed within 3 months and in longer than 15 months after final irradiations in both groups. The mice exposed to 3Gy had cells with abnormal chromosome no. 2 more than those exposed to 4×1.7Gy did. The number of cells with chromosomal abnormalities in general increased at the late stage in the mice given 4×1.7Gy, but not in the mice received 3Gy. The chromosomes whose frequencies exceeded mean plus two times the value of standard deviation were the chromosome no. 2 in the former and the chromosome no. 11 in the latter.
Somatic chromosomes of two species in the genus Enhadra are studied using air-drying methods. The diploid numbers of both E. callizona and E. p. simodae are 2n=56, and are the same as other Euhadra species described in Inaba's report (1959) and in our previous papers (1984, 1987). From the karyotype analysis of the two species E. callizona is found to have 19 pairs of metacentric and 9 pairs of submetacentric chromosomes, E. p. simodae bears 18 pairs of metacentric and 10 pairs of submetacentric elements. The differences in the karyotypes of these two species suggest that they differ from each other cytogenetically. E. callizona is found to bear a karyotype resembling that of E. dixoni and E. amaliae (1984, 1987); the similarity of form suggests that it is closer to those two species cytogenetically. The karyotype of E. p. simodae is found to have some different elements to that of E. c. hickonis in the medium- sized and the small-sized chromosomes, and is therefore shown to be distinct from E. c. hickonis cytogenetically.