1. A case of functional disturbance of the plastid system, found in Medicago truncatula Gaertn., is described. Its most striking aspect was a widely varying variegation, hence the term “variegation sensu lato” would be convenient.
2. The phenomenon is controlled by a variable recessive gene. The spectrum of its manifestations extended from colorless albina, bordering on xanthoid-over gradually varying degrees of variegation-to apparently homogeneous green.
3.Selection was successful in both directions. If practiced toward increasing participation of the green component, it resulted in a uniformly, somewhat lighter, green form which could be distinguished from the normal green of the Bright line mainly by ±quasi-chlorotic new growth. The selection was aided by a greening process imposed by the same gene. Selection in the opposite direction, toward the albina state, made the maintenance of variegated plants possible. But it was difficult to reach the albina state itself by selfing, unless strikingly variegated pods were used which offered the chance for the occurrence of ovules formed in colorless or ultra-chlorotic tissue. The easiest way to obtain highly variegated plants as well as albinas was to look out for them in crosses, for the former in the F₂ generation and for the latter in any segregating offspring in F₂-F₅.
4. Crosses with the normal Bright line showed in both directions of the cross very similar results. In F₁ (about 50 plants observed) normal green was completely dominant. In F₂ segregation was monohybrid but a considerable part of the recessives were albina, more of them in the cross with normal green as the female parent of the cross, (among 42 recessives 20) than in the reciprocal direction (among 42 recessives 13).
5. In the further generations, F₃-F₅, albinas were almost the only representatives of the recessive class, i.e. variegated plants practically disappeared. Thus, the problem of the variable gene of the present case was, after the branching off of a normalized form, resolving itself in the course of generations into the old Mendelian example of 3 green: 1 albinotic segregation.
6. Segregation was recognized already among the seeds of hybrids, due to the “greenish” appearance of the albina seeds. The difference from normal seeds (homo- and heterozygotes) was much more pronounced in the first green stager¹⁾, in still green pods, where the contrast between the scarcely perceptible tint of the albina embryonal cotyledons and those, lusciously green, of the dominant homo- and heterozygotes was striking. Occasionally a variegated pattern of the cotyledons could be seen in the first green stage of F₁-seeds.
7. The plastids seem to be potentially able to function. Only those in ultra-chlorotic and albina tissues remain inactive.
8. A tentative explanation of the albinas in the segregating offspring was sought in an eventual intra-pod competition. Their higher frequency when normal green was the female parent of the cross than in the reciprocal direction seems to be not inconsistent with this hypothesis.
9. The described case is gene-controlled. Crosses with normals gave in both directions of the cross the same results. Intra-cell mixture and its corollary, somatic segregation of plastids, seem not to occur. Plasma has no influence, in contradiction with variegation resulting from the fairly well understood chimeral developments inwhich a maternal plasma is involved. Both kinds of variegation could be simultaneously observed in the present investigation. The difference was striking.

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Aspects of Drosophila populations in a semi-natural state carrying various kinds of vegetations in the University Gardens at Sapporo were investigated during the years 1953 through 1962. A general account of the Gardens and some of the climatological features are described. For this study collections of drosophilid flies on a large scale have been done with the use of banana traps at a single site during the ten years. Collections were made monthly from May to October, except in 1953 and 1955. These collection dates and times are shown in Table 1. In 1959 differential attraction of drosophilid species to five different kinds of yeasts was examrnd using fermenting banana bait, in which the test yeast was actually growing, at three different sites in the Gardens.
During the period of this survey, a total of 46, 619 specimens of fourty-three species of Drosophilidae was obtained by the method of trapping. These collection data were summarized in Table 3.
Population sample obtained from the semi-natural areas in traps of banana bait, has been constructed from two “abundant”. seven “common” and thirty-four “rare” species. Relative frequencies of the thirteen leading species are shown in Table 5. Among the “abundant” and “common” species, D. auraria race A (a representative of the auraria species population in this Gardens), D. nigromaculata, D. lutes, D. brachynephros, D. immigrans and D. suzukii have been found to be domestic forms closely associated with man, while D. testacea, D. bifasciata and D. lacertosa have had wild habitats throughout Hokkaido. Yearly changes in the relative frequencies of abundance of these species were more conspicuous in “common” species than in “abundant” ones. Mean humidity and rainfall shown by each year or each collecting season during the ten years seem to exert no influence upon the relative frequencies of these drosophilid species. Variations in the other environments in this Gardens may occur from year to year affecting such frequencies of Drosophila species.
The distribution and preferences to yeast of drosophilid species in this Gardens are described. Abundant and more common species showed generally larger adaptive abilities in relation to the collecting sites and to the yeasts than less common species so far investigated. Percentage frequency of females in total drosophilid flies sampled by banana traps during nine years (1954-1962) was 45.61. Only one species, D. testacea, among the “abundant” and “common” species showed female superiority with the frequency of 59.85 percent. Sex-ratios of most of the species seem to be affected more or less by collecting site and yeast attractant.

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For collection of flies which are insensitive to baits, a considerable amount of net sweeping was carried out on many kinds of fungi and grasses in the University Botanical Gardens at Sapporo, 1953. Twenty-two and eleven drosophilid species were obtained on six kinds of fungi and five kinds of grasses respectively. Most specimens observed in the samples belonged to D. trivittata, D. sexvittata and D. brachynephros for fungi, and D. nipponia, D. nigromaculata and P. pallida for grasses. Differential attraction to different kinds of fungi and grasses was indicated by the drosophilid species. Most of the species collected by sweeping except a few species have been scarcely attracted to fermenting fruits such as banana bait. It is evident that D. nigromaculata which was one of the “abundant” species among the trapped sample, has had the most universal preference for various kinds of food in all species obtained from the Gardens in the present survey.

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A detailed analysis was made on the chromosome pairing at pachytene stage of the inter-specific hybrid of the cross O. sativa×O. officinalis, grown under different temperature conditions (20, 25, 30°C and natural condition).
At diakinesis and metaphase-I, ranges in frequencies of bivalent chromosomes per PMC was 0-11 (mean 0.77) and 0-5 (mean 1.08), respectively.
At diakinesis and metaphase-I, different temperature conditions (20, 25, 30°C and natural condition) had little influence on the formation of bivalent chromosmes.
From the results of pachytene analysis along with all other data, it will be favoured to consider that there exists partial homology between the chromosomes of two species, O. sativa and O. officinalis.

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The leucocytes in a small volume of peripheral blood obtained from tail vein of the mouse were cultured for the cytogenetical and radiobiological studies. The method and a preliminary result on chronically irradiated mice were described.

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The sex chromosomes of dds mice were investigated in testicular and spleen cells in males and in spleen in females with the application of an air-drying method.
The X would appear to be represented by the largest telosentric element, while the Y might be identified as a heteropycnotic and nearly telocentric one ranking in the three smallest chromosomes in male cells.

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人為同質四倍体と二倍体との交雑によってえられた, diplo-haplo 雑種における成熟分裂の染色体の行動を観察し, その半数染色体側のゲノム内対合 (intra-genome pairing) を知る目的で, 4x-Ae. squarrosa×S. cereale F₁ならびにそれに S. cereale を戻し交雑してえた BCF₁ 植物の成熟分裂を観察した. そして, S. cereale の R, Ae. squarrosa のDゲノム染色体間に, それぞれ1対のゲノム内対合の存在することを明らかにした. それはRゲノムでは2.8%, Dゲノムでは0.8%の PMC で観察された. これら二価染色体はまれにキアズマを形成することもあり, 染色体の相同性による対合と思われる. 2個体の BCF₁では, Ae. squarrosa と S. cereale の染色体間の異親対合による三価を, それぞれ2.4%, 1.8%の頻度で観察した. また, いずれの植物においても一価染色体のあるものが, たがいに連絡しているようにみえる univalent association もまれに見出された. これはヘテロクロマチンの接着による現象と考える.

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