The fine structure of the macronucleus of the gymnostome ciliate Chlamydodon pedarius at young stage and interphase approaching the division has been investigated by means of the electron microscopy.
The macronucleus comprises two different structures: the anterior half is less dense structure which consists of the diffuse filamentous matrix material, and contains one endosome composed of much dense filamentous material in its center; on the contrary the posterior half is a very dense structure, and consists of a reticulum made of very dense strands or cords, very dense nucleolar materials and little less dense matrix material. However, the fine structure changes in the stages of the young macronucleus and of the interphase approaching the division.
The nucleoli are distributed beneath the envelope with a short distance. The structure is composed of filamentous material, dense particles of various size, and less dense matrix in the young macronucleus, but in the interphase macronucleus approaching the division it shows very loose and vanishing structure of aggregate of granular texture. They do not have any retaining membrane always.
The longitudinal stripes of about 100mμ to 200mμ in width are found in the macronucleus approaching the division. They run parallel to the long axis of the macronucleus, seeming to contribute the elongation of the macronucleus, and are inferred to be preliminary form of the chromonemata in the very early prophase macronucleus.
The highly electron-scattering threads of the order of 25mμ to 30mμ in thickness and the electron-dense helices of about 15mμ to 20mμ thick are found in the corresponding places to the DNA containing elements of the macronucleus, and the filament making up them seems to correspond to a nucleoprotein complex. It is possible, consequently, to draw the following conclusions: The individual thread appears as a result of duplication of the filament; the strands in the young macronucleus are fragment of the chromonemata; the cords constituting the network of the posterior half represent the chromonemata in the interphase or very early prophase macronucleus.
The structure of an envelope enclosing the macronucleus is composed of double membranes of about 50Å thick respectively, separated by a space of about 200Å wide, and numerous penetrating pores of about 400Å diameter in normal area.

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A number of larvae showing the Nl phenotype were obtained by irradiation of E^HE^Kp/E^HE^Kp individuals. The three Nl types, Nl, Nl¹ and Nl², were investigated. From crossing experiments, it is assumed that Nl mutants are caused by deficiencies in the part of the 14th chromosome which includes the oa locus and that the order of their relative lengths for the three types is Nl>Nl¹>Nl².
It was observed that embryos homozygous for Nl¹ die at a far more advanced stage than embryos homozygous for Nl and that the development of the embryos homozygous for Nl² advances still a little further. Thus, the difference in the extent of the deficiency in each of the three Nl mutants relates to the stage at which the respective homozygous embryos die.
Spontaneous Nl type mutation occurs very rarely. However, it may be said from the present experiment that the frequency of the mutation increases strikingly as a result of irradiation with X-rays and that the extent of the deficiency in each of the Nl type mutants is not always the same.

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The conversion of sepiapterin by pterine reductase obtained from Drosophila melanogaster was investigated biochemically. Molar ratio of reduced triphosphopyridine nucleotide as a cofactor to sepiapterin as a substrate on this enzymatic reaction, was 1.0. The spectra of the reaction product were very similar to those of tetrahydropteridine. These facts suggest that the reaction product is tetrahydrosepiapterin.
The products further converted from the tetrahydrosepiapterin by non-enzymatic oxidation were analyzed biochemically. In the absence of oxygen, the main product, compound A, was indistinguishable from biopterin in the chemical natures examined. In the presence of oxygen, the products of 2-amino-4-hydroxypteridine and 2-amino-4-hydroxypteridine.6-carboxylic acid were confirmed.
From these experimental results, the metabolic relationships among pteridine derivatives found in Drosophila were clarified. A plausible scheme of pteridine metabolism is as follows:
Sepiapterin_??_Tetrahydrosepiapterin_??_[Dihydrobiopterin]_??_Biopterin
2-amino-4-hydroxypteridine

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Ten different antigenic factors were found by isoimmunization in the erythrocytes of the chicken. Genetic analyses showed that these antigenic factors were controlled by genes belonging to three non-linked loci, which were designated F, G and H. One of these, namely G, consisted of nine alleles G^A, G^BM, G^C, G^G, G^I, G^K, G^L, G^M and G^g, and the other two loci consisted of two alleles each-F^F and F^f, and H^H and H^k, respectively.

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H₁ inactive mutants from diphasic strain of S. typimurium perform O-H variation in place of phase variation. Phase-1 is O type and phase-2 is H type in such mutants. The functions of H₁ and H₂ are duplicate in flagellar production.
The activity of H₁ is controlled by Ah₁, which is closely linked to H₁ but separable from it by recombination. The mutation of Ah₁⁺ to Ah₁^- causes the inactivation of H₁. The mutant sites of three Ah₁^- strains differ from each other in a single cistron, and they have different potentiality of reversion.

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Investigation of segregation in respect to seed-coat color in F₂ of 22 different hybrids was made, which were originated from crosses among 20 varieties of Japanese and foreign origin, including 3 red-grained, 1 brown-grained and 16 white-grained ones.
In the crosses red-grained (Rc Rd)× white-grained (rc rd) F₂ segregation took place normally, i.e. red:brown:white=9:3:4. Other crosses between red (Rc Rd) and white (rc Rd) gave the ratio approximately red:white=3:1, but there were always found a small number of unexpected brown segregants, showing the possibility of occurrence of plants lacking Rd-locus. In the crosses red (Rc Rd)×red (Rc Rd) also a few number of unexpected brown segregants were noticed.
Discussion was made as to the mechanism which resulted in the appearance of segregants lacking Rd-locus. It has been suggested that the cause might be due to occurrence of auto-and allosyndesis, involving the chromosome which bears Rd-locus. The partner of the Rd-bearing chromosome in autosyndesis can, however, not be identified.
The genotype of brown-grained variety, Surjamkhi, was determined as Rc^dRd, Rc^d being a new allele at Rc-locus. The multiple allelic series here proposed is as follows; Rc>Rc^d>rc.

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1. In the present report, the external characteristics, the number of somatic chromosomes and the meiosis in PMC's of a plant, thought to be raised from natural crossing SfHvF₁ with Secale africanum growing around it, were described, and the plant will be represented as SfHvSaF₁-1.
2. The somatic number of chromosomes of the SfHvSaF₁-1 plant was counted to be 21 (Fig. 1). This was probably caused by the fertilization of the female gamete of the SfHvF₁ plant (2n=14) having 2n chromosomes with pollen of S. africanum (n=7) growing around it, viz. 14+7=21.
3. The culm height of SfHvSaF₁-1 was intermediate between the parents, but it was much inferior to that of SfHvF₂ plant, while the length of spikes shows almost the same value to that of the SfHvF₂ plants. The length of awns was intermediate between the parents, but it was inferior to that of SfHvF₂ plants. The number of spikelets and spike density are rather closely resembled the SfHvF₁ as the mother plant, but these were considerably superior to those of SfHvF₂ plants. The number of florets per spikelet was inferior to that of the mother plant (SfHvF₁), but its value was almost the same as that of the pollen parent. The number of tillers was somewhat superior to that of the SfHvF₂ plant but it was considerably inferior to that of the parents.
4. The number of chromosomes in PMC's was 21 in the total as the 2n number (Figs. 2-9). Among them 7 chromosomes most probably have been derived from pollen parent, S. africanum (n=7), and also the remaining 14 must have been derived from the mother plant, SfHvF₁ (2n=14). Therefore, the genomes of this plant, SfHvSaF₁-1, will be VR^aR^f.
At MI of PMC's 0-7 bivalents were found. Their frequencies are shown in Table 2. The mode of occurrence of bivalents was 5, and average value of the bivalents was 3.85.
Most of the bivalents may be caused by the syndesis between the chromosomes of R^a and R^f genomes of S. africanum and S. fragile respectively.
Trivalents besides bivalents were rarely observed.
5. This SfHvSaF₁-1 plant was completely sterile.

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Some effects of X-rays and Nitromin upon the MTK-sarcoma III, an ascites tumor of the rat, were cytologically investigated after single and combined applications.
Intraperitoneal injections of Nitromin at a dose level of 2mg/kg were made in tumor-bearing rats on the 3rd day of transplantation. The X-rays were given with the whole body exposure at a dose of 1, 500r for 5 minutes and 36 seconds under the same condition as above. Tumor samplings were made from treated animals at 3, 6, 12, 24, 48 and 72 hours after single and combined applications of X-rays and Nitromin. The preparations of tumor cells for cytological observation were made by means of the water pre-treatment squash method, with acetic dahlia or acetic orcein. For detailed morphological observation, May-Grünwald-Giemsa staining method (Jacobson and Webb 1952) was adopted.
The following cytological injuries were observed as criteria for affected tumor cells after the treatments: 1) changes of mitotic frequencies, 2) occurrence of micronuclei, 3) frequent occurrence of translocation and fragmentation of chromosomes in metaphasic cells, 4) formation of bridges and acentric fragments of chromosomes in ana- and telophasic cells, and 5) pycnotic cells.
It was shown that the destructive action of Nitromin to tumor cells generally differed from that of X-rays in morphological and statistical detail. Apparently the effects of Nitromin were always far more durable than those of X-rays. Probably, Nitromin causes the cell-damage in close association with a non-specific metabolic disturbance of the cytoplasm. On the other hand, X-ray irradiation affected directly the nucleus at each phase of cell division except telophase. X-rays in combination with Nitromin induced a complete tumor regression in significantly large number of cases, in which cytological damaging effects were quite remarkable as a result of combined actions of two agents.

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The salivary gland chromosomes of 263 larvae of D. immigrans obtained from several natural populations in southern-central districts of Japan were examined. Three different types of heterozygous inversions occurring in the second chromosome were observed, and the mean frequency per larva was 0.19. These inversions seemed to be similar to those reported by Freire-Maia and Brncic in natural populations in Brazil and Chile. This species would be sensitive to certain climatic conditions because of its poor chromosomal polymorphism.
The variation in number of collected flies was also observed in relation to seasonal changes and the elevation.

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