Natural populations of diploid organisms are expected to be more polymorphic than haploid organisms under most selection models. To test this prediction and to obtain data concerning the amount of allozyme polymorphism in a haploid plant, I examined two natural populations of the haploid liverwort Conocephalum conicum by starch gel electrophoresis. Abundant genie variability was found within local populations in Japan: 7 of 11 loci. Average heterozygosity of these 11 loci was 0.167. This value is similar to those obtained for various kinds of diploid organisms. Gene identity (I) between the two populations was 0.994, and another measure of genetic differentiation, G_st was 0.018, indicating virtually no genetic differentiation between the populations. High levels of genie variability and low levels of genetic differentiation in these haploid plants are consistent with a hypothesis of selective neutrality of allozyme polymorphisms, although other possible explanations cannot be excluded.

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Four monosomic substitution lines of the Elytrigia elongata (=Agropyron elongatum) chromosomes, e₂, e₃, e₆ and e₇ for chromosome 4A of durum wheat were produced by the cross between monosomic 4A and the corresponding disomic addition lines of Stewart durum. Among them the monosomic substitution line e₇(4A) was the most vigorous and fertile. Although this line showed a chromosome configuration of 13″+2′ at the first meiotic metaphase, it had 14 bivalents at diakinesis in most of its pollen mother cells. The fertilization rate of the four types of the egg cells produced by this monosomic substitution suggested a 50% elimination of both e₇ and 4A univalents during the meiosis of durum wheat. Male transmission behavior indicated that chromosome e₇ compensates for the function of chromosome 4A in the certation. A disomic substitution line was selected from the progeny of the monosomic substitution line e₇ (4A). Plants of this line were vigorous and completely fertile. Chromosome e₇ was found to have a structural gene for alcohol dehydrogenase; in wheat this gene is known to be located on the three chromosomes of homoeologous group 4. It was thus concluded that chromosome e₇ of E. elongata belongs to homoeologous group 4. A comparison of the morphology of the substitution, addition and monosomic lines with those of the normal Stewart durum, showed that chromosome e₇ carried genes for awn suppression, culm thickness and ear laxness.

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The chromosome numbers in two species of snipefishes, Macrorhamphosus sagifue and M. japonicus, are found to be 2n=48. These two species are karyotypically indistinguishable from each other.

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Coat color genes of mutant ddY/DAO^- mice that do not have D-amino acid oxidase were examined by crosses of these mice with NC (AAbbCC) and II TES (aabbCCddss) mice. All the (ddY/DAO^-×NC)F₁ mice had agouti coats and the (ddY/DAO^-×II TES)F₁ mice had black coats. These results indicate that the ddY/DAO^- mice carry aaBBcc DDSS gene.
Linkage relationship of Dao-1 gene coding for D-amino acid oxidase to coat color genes was examined. Segregants produced from backcrosses of (ddY/DAO^-×IITES)F₁ with ddY/DAO^- and (ddY/DAO^-×NC)F₁ with ddY/DAO^- were examined for D-amino acid oxidase activity and coat color. F₂ segregants from a (ddY/DAO^-×NC) cross were also studied. These crosses showed that Dao-1 was not linked to a, b or c.

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This paper presents genetic linkage data on an isocitrate dehydrogenase (Idh-1) and a tetrazolium oxidase (To-2) loci in the mosquito Aedes togoi, as well as a new linkage map of this species. Both isozymes (IDH-1 and TO-2) are dimeric; the Idh-1 and To-2 loci have been mapped together on linkage group 1 of all three linkage groups in this species (haploid chromosome number=3), as in the linkage map presented here. But correlation between these three linkage groups and the three chromosomes has not yet been established. The entire map of the three linkage groups has been marked thus far with 16 visible and 7 enzyme loci; its total map length is approximately 250units. Linkage group 1 is presently the longest, occupying 13 of all 23 mapped loci; this group contains the sex-determining (M) and an acid phosphatase (Acph) loci near its middle, which is the situation similar to linkage group 1 of Aedes aegypti.

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Interspecific crossability between Drosophila kanekoi and other members of the D. virilis group was studied by using no choice and female choice methods. Asymmetric mating preference was observed in every cross. Females of D. kanekoi more frequently mated to males of D. virilis, D. lummei and of D. montana montana than in the reciprocal crosses. A complete sexual isolation was found between two sympatric species, D. kanekoi and D. ezoana.

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A dominant mutant Asc (KH2A83), defective in ascospore formation, was obtained as a spontaneous mutation by the application of allelic complementation between inl (37401) and inl (83201(t)). The heterozygous cross of this mutant with wild type as protoperithecial parent produced 10-40% of white abortive ascospores, and that with wild type as conidial parent formed 60-90% of white abortive ascospores. The homozygous cross of Asc (KH2A83) produced 90-95% of ascospore abortion. The mutation was mapped between his-1 and al-3 at a distance of 0.8% to al-3 on LG VR. The UV sensitivity of Asc(KH2A83) was 2.8-4.0-fold higher than that of wild type, but that of Mei-2, mapped near al-3, was 2.3-fold. Whereas, unlike Mei-2, Asc(KH2A83) did not show sensitivity to methyl methanesulfonate and to histidine. Conidia of Asc(KH2A83) showed about 1% of viability in sorbose agar minimal medium, but those of Mei-2 did not show such character. Markers near Asc (KH2A83) including al-3 and inl represented low recombination recovery rates (2.6-28.9%) indicating reduced viability of ascospores which included
Asc (KH2A83). The aneuploid formation in a heterozygous cross with Asc(KH2A83) as a protoperithecial parent was estimated to be 0.9%.

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