The floating habit of 10 strains belonging to Oryza sativa, O. perennis or O. glaberrima was studied by sinking them up to 3m deep in water at 6 different rates, namely, 0 (control), 1.5, 3.1, 4.6, 6.2 and 9.3cm per day. Number of days of floating, plant height, leaf length, total internode length, number of internodes and average internode length were observed.
From this experiment the following results were obtained.
(1) The 10 examined strains can be classified into 3 groups regarding thefloating habit. Strains 1 and 2 of O. sativa and strain 5 of O. perennis were pronouncedly floating, strains 6 and 7 of O. perennis and strain 8 of O. glaberrima were weakly floating, and strains 3 and 4 of O. sativa and strains 9 and 10 of O. glaberrima were non-floating.
(2) In the pronounced floaters the increase in plant height under flood conditions is almost entirely dependent upon the increase of the total internode length but little upon length of a floating leaf. Effect of the latter is, however, rather important in the weak floaters.
(3) The increase in total internode length is almost equally dependent upon the increase in the number of internodes and their elongation.
(4) Internode length of floating rice types collected in their native places was extremely variable, while that of the experimentally raised plants was uniform. Length of almost all internodes of the collected plants falls within the range of the average internode lengths of the experimental plants raised in the control and a high sinking rate-plot.
(5) Rate of internode elongation increases, within a limit, proportionally with sinking rates. Floating habit of individual strains can be characterized by 3 factors, a, b and c, which determine a regression of the rate of internode elongation on the sinking rate. Factor a, indicating the rate of internode elongation achieved under normal conditions, can be used as an index of resistance against a sudden flood. Factor b represents the slope of the regression line and indicates the capacity of a strain to elongate the internodes in correspondence to water raise. The third factor c represents the maximum rate of elongation.
(6) Analysis of those 3 factors is a useful means to characterize the floating habit of individual strains. Among the 3 pronounced floaters, strain 1 has an extremely large a and the smallest b, being most resistant against a rapid sinking for a short period. Strain 2 is characterized by the smallest a and c and a much larger b than that of strain 1. Strain 5 has the largest b and c and is most resistant to a chronic flood condition. All 3 weak floaters have only small a and c but their b's are almost comparable to those of the pronounced floaters.

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Fifty amylase deficient mutants have been obtained independently from the wild strain of Aspergillus oryzae by using the filtration-concentration technique (eliminating conidia in the minimal solution supplemented with starch or amylopectin as a carb on source) after UV irradiation. These mutants do not grow on the medium containing starch but grow on glucose. Genetic study for amylase production was carried out through the parasexual cycle by using twenty-five mutants.
All twenty-five mutant genes are recessive to normal ones. Amylase production is controlled by genes at two loci; one locus (ae) contains twenty-four alleles (these mutant genes show negative or diminutive in both their dextrinizing power-DP and Saccharifying power-SP) and another locus (ae') includes one allele (the mutant gene shows normal in its DP but not in its SP).

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The gametic-development gene hypothesis, formerly put forward by the senior writer, could convincingly explain the sterility of F₁ hybrids and related phenomena in cultivated rice, but could not account for the occurrence of sterility in F₂ and later hybrid derivatives. It was found that among many intervarietal crosses, F₁ fertility and mean F₂ fertility were not correlated. Experiments were then conducted to throw a light on the genetic basis of sterility of the latter type, using cross combinations which showed a high fertility of F₁ hybrids. Their fertility in F₂ segregated in a wide range, and from a few partially sterile F₂ plants, partially sterile lines which bred true for sterility have been established. Embryological observations showed that both male and female gametes partly degenerate after normal meiosis.
The partially sterile lines were then back-crossed to the parental strains, and the F₁, F₂ and F₃ generations were investigated regarding fertility variation. The results led to the conclusion that duplicate factors might be involved sustaining the development of gametes on the condition that at least two dominants are present in the plant, and that this diplontic sterility might be due to certain recessive combinations of those factors. The parental strains were considered to have different combinations, A₁A₁a₂a₂ and a₁a₁A₂A₂. A linkage relation was found between such a fertility factor and the apiculus pigmentation gene C. In the sense that those factors behave as genes, they were called Duplicate-fertility genes. The genetic basis of this sterility thus postulated is similar to that formerly shown for the segregation of weak plants in F₂. Both phenomena, which spell a breakdown of hybrids, seems to be the isolating barriers frequently found in rice.

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1. Lethal chromosome frequencies, the allelic rates of lethal genes and homozygous viabilities of quasi-normal chromosomes were estimated in the second chromosomes extracted from four natural populations of D. melanogaster distributed in the western and central parts of Japan.
2. The combined frequencies of lethal and semi-lethal chromosomes in each population were 15.1, 15.7, 7.3 and 20.1 per cent respectively. The mean viabilities of quasi-normal chromosomes in three populations were about 32 per cent. The allelic rates within population in the three populations were 5.3, 4.1 and 7.0 per cent respectively. Based upon these data, the Japanese natural populations were regarded to besmall in their sizes.

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Twenty isoleucine and valine requiring mutants including a temperature mutant were found to be separable into three groups genetically, I, II and III. The mutants are located at sites distal to lysine-1 and proximal to spray in linkage group V in the order III, II and I. This arrangement of the groups is of particular interest when considered in conjunction with the biochemical characteristics of the mutants.
Certain unexpected ratios of recombinants with respect to outside markers are noted and discussed. In addition selfing crosses are described some of which resulted in a high frequency of progeny with a wild phenotype.

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The chromosomes of five species of beetles have been studied in male germ cellswith particular reference to the number, morphology, behaviors of chromosomes and the sex-determining mechanism. The results of observations are summarized in Table 2. The X-chromosome in H. macroderus is always found lying off the plate at the first metaphase.

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X線の畸型形成効果を利用し, ハツカネズミ胚の発育過程におけるX線の影響とくに受精後の照射時期による異常形質の出現について観察し, さらに平均胎児数, 性比, 体重および体長と尾長の比について調査した。
ハツカネズミ (Mus musculus) はB72 の雌および Swiss albino の雄を使用し, 受精後0.5日目から15.5日目までの間にそれぞれ1回, 妊娠母体に 200r のX線を全身照射した。
異常形質の出現頻度: 受精後種々の時期に照射されて得られた 166 個体の胎児の中, 46 個体(27.7%)の異常胎児が発見された。異常胎児のすべては受精後8.5日目より 12.5 日目までの間に照射されたものである。得られた異常形質は無眼症, 脱脳症, 鼻部の異常, 過剰指, 欠除指, 癒合指, 短尾, 変形した尾, 肛門の異常であった。これら各種の異常形質は, それぞれ受精後, 特定の時期に照射をうけたものにみられた。
1腹あたり平均胎児数: 対照区における胎児数と照射区における出産直前の1腹の平均胎児数は前者6.0に対し後者5.1で, 両者の間に大きな差はみられなかった。
性比: 対照区より得られた雄の比率は 56.7%, 照射区におけるそれは 54.8%で, 両者の間に明らかな差はみられなかった。
体重: 受精後8.5日目より 12.5 日目までに照射をうけた胎児は対照区の体重より顕著な減少を示しており, その後に照射したものは次第に体重を増加し対照区に近づいている。
体長と尾長の比: 対照区では 2.1～2.5 を示したが, 受精後 8.5 日目より 12.5 日目までの照射区では2.6以上の比を示す短尾が多く現われた。

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1960年著者らによって決定された Chenopodium 属植物の染色体数は第1表のとおりであり, Chenopodium 属植物の染色体数の基数は8と9であって既報 (川谷•大野 1950, 1956) と変わらない。

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The reduction division in PMC's was studied in 5 interspecific hybrids: N. suaveolens× N. plumbaginifolia, N. suaveolens×N. longiflora, N. gossei×N. plumbaginifolia, N. gossei×N. longiflora and N. gossei×N. alata. N. suaveolens and N. gossei are Australasian species and N. alata, N. plumbaginifolia and N. longiflora are American species. These five plants are low chromosome number species and have a similar external morphology.

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1. Capsicum annuum L., C. frutescens L., C. pendulum Willd., C. chacoense Hunz. およ??攀??椀?? C. pubescens Ruis et Pavón について, 開花から完熟に至るまでの, 辛味成分 capsaicin の果実乾物重当りの含有率, および1果当りの総量の生成消長について調べ??攀??椀?? (第1表および第1図)。
2. 開花後1週目で♯?攀??椀?? C. chacoense にのみ若干??攀??椀?? capsaicin が認められ, 他の4種ではいまだ辛味成分は分泌されていない。これら4種でも, 2週目には若干の分泌が認められた。
3. 乾物重当り??攀??椀?? capsaicin 含有率の最大は, C. chacoense では開花後2週目, C. annuum では3週目, C. pendulum ??攀??椀?? C. frutescens では4週目にあるが, C. pubescens では5週目でもなお最大に達していない。この5種の序列は, それぞれの種の生育適温要求度の序列と一致した。
4. C. pubescens 以外では, 開花後4週目ごろには果実はまだ未熟であるが, その果実として??攀??椀?? capsaicinはほとんど分泌されている。したがって辛味のみを利用する場合には, 開花後約1カ月程度の未熟果を収穫すればよい。
5. 近縁•野生種利用の育種の観点からは, より辛いトウガラシの育成に♯?攀??椀?? C. frutescens を交雑育種の母本として用いるのがもっとも有望であると考察される。

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