On the sex discriminating method by coloring .genes of silkwdrm eggs. 1. Induction of translocation between the W and the tenth chromosomes.

In order to discriminate femalenness and maleness of the silkworm even in early egg stage, an experiment was planned with X-ray treatment to join a fernale deter, mining gene and a normai aliele to white egg color (white-2, 2) by mutuai trans-location between the Wand the tenth chtomosomes. Such translocat:ion night bepected by X-rayin the heterozygols w, females (w./-F, Z/W) in early or mid pupal stage, when the erly prophse of the maturation division of the oocyte is going on. The irradiated females were back crossed to w. males, and all the fenale offspring from such crassing. were tested by crossing them to white and translucent males (w/w2' Z"d/Z"d) of their genetic construction. Among 6523 batches yielded from the same numbers of ferilale parents of BF2 of which genotype-analyses were carried on, only one batch showed an expected type of translocation and it was confirmed by her progeny test. This is the type of translocation that we have expected for this experiment. The frequency and the proba-bility of its appearance were discussed. The high rateo, apearance beyond our expectation muse be noticed.