Impaternate Females in Habrobracon

1. Impaternate females, produced by virgin mothers, constitute on the average .702 per cent of the F 2 from outcrosses of tapering and reverted tapering females. 2. The constitution of the parental male, as well as the female, affects the ratio of F 2 females. 3. When F 1 virgins from outcrosses of tapering or reverted tapering females were X-rayed, the percentage of F 2 females fell to .164. 4. When tapering and reverted tapering females were inbred, the percentage of impaternate females in the F 2 was only .006. 5. The ratio of impaternate daughters decreases with increasing age of the mothers. 6. No impaternate females occurred in the F 2 from tapering males by type females, from shot-veins or Minnesota-yellow females by various mutant males, or from impaternate females by their brothers. 7. Enough impaternate females were produced by virgins heterozygous for one or more of five different recessive factors to indicate how frequently those loci undergo reductional or equational first divisions in the formation of the secondary oöcytes from which the impaternate females are assumed to arise. 8. For four of the five loci best tested the percentage of females homozygous for the recessive factor did not differ significantly from that of females homozygous for the dominant allelomorph, nor did either of these differ significantly from 25 per cent of the total. These results would be expected if crossing-over were always between diagonal strands and equational and reductional divisions occurred with equal frequency for any locus. 9. For the fifth locus, orange, homozygosis for the recessive was 16.5 per cent (25 – 8.5); homozygosis for the dominant allelomorph was 34.3 per cent (25 + 9.3). 10. The fact that homozygosis was well over 16.6 per cent except in the case of the orange recessive indicates that random assortment of the strands of a tetrad does not take place. 11. Impaternate females in the F 2 from tapering females by males carrying linked factors show that crossing-over occurs in the four-strand stage. 12. Two gynandromorphs were obtained from virgin mothers. Presumably they involved three haploid sets of chromosomes, two in one nucleus giving rise to female regions and a third in another nucleus forming male regions.