The variability of the race C of Drosophila auraria has been discussed with regard to intraracial sexual isolation.
Occurrence of intraracial sexual isolation between strains was detectable in many cases.
The relationship between variability in the degree of sexual isolation and that in the sixth sternite bristles of male flies was found to be parallel in some cases.
The geographical distribution of the strains is thought, however, usually to stands in a casual relationship with the degree of sexual isolation.
Certain intensification in the degree of sexual isolation with time during which the flies have been kept in the laboratory stocks was recognized.

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1. The relative viability of brown homozygote was measured in various levels of larval population density which paralleled with the number of female parents in a culture bottle. The results were shown in Table 1 and Fig. 1, and confirmed the fact that the superiority in viability of brown homozygote increased with larval population density.
2. Two series of competition experiments were conducted: series S, in which ten or less parental flies were sampled generation after generation, and series L, in which generally larger number of parents were sampled. By assuming that the zygotic selection coefficients were determined only by the relative viability of three genotypes, and by using Fig. 1, random change in frequency of brown genes were calculated from generation to generation.
3. In both series the distributions of the amounts of random change relative to expected standard deviation of change in gene-frequency could be regarded to have mean values of 0. This result showed that the above assumption was practically correct.
4. Average effective population size (N) was considered to be smaller than average apparent size (N") on account of, at least, three factors, i, e., (i) the departure of parental sex-ratio from one-to-one, (ii) the variability of the numbers of progeny of each parent and (iii) the parental inbreeding. Thus, the formula
N=αβN".
was presented, where α (0<α≤1) and β (0<β≤1) were the coefficients measuring influences of the factors (i) and the other factors, respectively.
5. The values of α and β, and those of their poducts were calculated as follows:
Series S: α=0.84, β=0.35-0.62, αβ=0.29-0.52.
Series L: α=0.92, β=0.22-0.30, αβ=0.20-0.27.
The values of β, especially in series L, seemed to be too small in comparison with the results of several antecedents. It could be interpreted, at least in part, as a result of circumstances that the number of effective parents was only a small fraction of total parents sampled; and such circumstances were considered to be remarkable in crowding condition as in series L.

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Dry and soaked seeds of several varieties of rice plants were irradiated with various degrees of doses at 120KVP, 3mA, distance 26cm., no filter. Results of cytogenetical observation of various sterile plants caused by the chromosomal aberrations were briefly summarized as follows:
1. About 68 per cent of the chromosomal aberrations observed was the interchange heterozygote including (4) and (4)+(4), and about 32 per cent was trisomics, asynapsis, syncyte formation and polyploidy.
2. The interchange heterozygotes were divided into several types based on the frequencies of ring or chain formation of four chromosomes at diakinesis.
3. The fertility (seed or pollen) in the interchange heterozygote rans approximately parallel to the frequency of side-by-side configuration of the interchage complex at metaphase-I.
4. Fertility in the progeny of the selfed interchange heterozygote differed from plant to plant, that is, some plants divided into two fertility groups, high and low, and other one showed continuous deviations.
5. In the progeny of the selfed interchange heterozygote, plants with RT (interchange heterozygote) and without RT (non-interchange heterozygote) showed the segregation of 1:1 ratio.
6. In the same interchange heterozygote, there was such a case showing much difference in distribution of fertility and segregation of the interchange heterozygote.
7. Asynapsis and syncyte formation were observed. Especially, the latter is the first example in rice plants.
8. Polyploidies, such as haploidy, triploidy and tetraploidy, have also been isolated from the progeny of X-ray irradiated rice plants.

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1. In 1957 a number of the medaka (Oryzias latipes) having vertebral anchylosis resembling the genetic fused (f) were found in a certain region on the outskirts of Nagoya. Characteristics of the “wild fused” and the genetic fused (f) are presented.
2. Breeding experiments performed on the genetic fused (f) confirm Aida's (1930) conclusion that it is a Mendelian recessive and independent from known color genes and the sex.
3. Breeding experiments with the wild fused indicated that the vertebral anchylosis is nonheritable. These anomalies might have arisen from some unusual environmental condition during embryonic life.
4. Artificial induction of nonheritable anchylosis is successfully performed by treating early embryos of normal strain with phenylthiourea.
5. It is pointed out that there are two kinds of vertebral anchylosis in this fish, i. e., hereditary and nonheritable.

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1. A silkworm strain showing dilute yellow larval color was found and the genetic constitution of this strain was confirmed to be lem/lem; d-lem/d-lem, whereas that of lemon strain was lem/lem; +^d-lem/+^d-lem. The d-lem gene belongs to the 2nd linkage group, and is allelic to the i-lem gene.
2. For the purpose of studying the manifestation mechanism of dilute lemon gene (d-lem) experiments were carried out.
3. The amounts of yellow pigment obtained from lemon larvae is about three times as large as that from dilute lemon larvae.
4. The amount of isoxanthopterin obtained from lemon larvae as well as from dilute lemon larvae is much smaller than that obtained from the normals. Furthermore, it was found that the hypodermis of dilute lemon larvae contains a smaller amount of isoxanthopterin than that of lemon larvae.
5. None or very weak pterine reductase activity could be detected in dilute lemon larvae like in lemon larvae. Thus, no significant difference has been found in the activity of pterine reductase between lemon and dilute lemon strains.
6. To test whether or not inhibition occurs at the step from a precursor to yellow pigment, a cross between normal and dilute lemon strains was carried out and the amount of isoxanthopterin contained in normal larvae which segregated in the F₂ generation was determined by single measuring method. No clear-cut evidence of inhibition of pteridine metabolism by d-lem gene could be obtained.
7. It is inferred from the experimental results that the following explanation is most plausible. Though the yellow pigment is normally produced, a large part of it is lost from the hypodermal cells owing to a defect caused by the d-lem gene in the system which keeps this compound within the cells. It is inferred that a certain protein is an important factor in combining with yellow pigments and keeping them within hypodermal cells.

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1. Diploid oats of an early mutant strain was grown for some generations in granite sand supplied with Kasai's nutrient solution or with that lacking phosphate. The latter showed typical symptoms of P-deficiency or inhibition of plant growth. However, no evident effect of P-deficiency was found on chromosomal abnormalities or gene mutations.
2. When young panicles of these P-deficient plants were irradiated with 250r of X-rays, the panicles in the full growth were apparently shorter than those of the plants which were not irradiated. Also a slight increase in the frequency of chromosome aberrations in the pollen mother cells of P-deficient plants was observed.
3. Dry seeds obtained from P-deficient plants were irradiated with 10-70kr of X-rays. No seedling could come out of sand by irradiation with a dose of 40kr or more. In 16 day old seedlings, P-deficient ones showed a higher radiosensitivity than the controls at the dose of 30kr, as indicated by the reduced survival rate and plant height in the former. A slight increase in mutation rate was found in the X₂ progenies of P-deficient plants though it was not statistically significant.

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1962年6月より10月までの間, 札幌市北海道大学付属植物園において, D. nigromaculata の染色体異常を調査した。47雌に由来する569個体の幼虫唾腺細胞を観察した結果, ほとんどすべての幼虫唾腺細胞に1または数個の逆位型が発見された。判別し得た逆位の型は32種であって, 豊福 (1962) が発表した22種と比較すると, 14種の新しい逆位型が発見された。33種の逆位は X 染色体に5種, A 染色体に10種, B 染色体に7種, C 染色体に8種, D 染色体に3種含まれていた。これらの逆位型の自然集団における出現頻度は季節の変化と関連しているように思われる。

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