N experiments already reported (RUSSELL and SAYLORS 1960; RUSSELL 1961 ) I we were able to induce loss of a sex chromosome by irradiating during the interval between sperm entry into the oocyte and the first cleavage. This interval is relatively long, and during a 4x-hour span within it, there is a change in sensitivity to sex-chromosome loss and to lethal effects. Since the chromosomal state o...
