In(1)sc4sc8/Ybb+ males and heterozygous In(1)sc4sc8 females have one NO (on the Y and on the normal X) and show a bb+ phenotype. In(1)sc4sc8/Ybb- males and X0 males carrying In(1)sc4sc8 are lethal. Magnification or increase in rDNA multiplicity may take place in In(1)sc4sc8/Ybb males, changing their phenotype from bb to bb+ (Tartof, 1971, 1973; Malva et al., 1972). In(1)sc4sc8/Y males frequently show correlated meiotic drive and nondisjunction (Peacock, 1965; Peacock et al., 1975), resulting in the recovery of more nullo than In(1)sc4sc8/Y gametes and more sc4sc8 than Y gametes. Distorted ratios result from sperm dysfunction which is proportional to the chromosome content of the nucleus (McKee, 1984, Genetics 106: 403-22). The extent of these meiotic irregularities is dependent on Y chromosome(s) present (Peacock et al., 1965) and the temperature at which meiosis occurs (Zimmering, 1963).