The main results obtained in the present investigation may be summarised as follows: 1) In the last premeiotic interphase the nucleus is of the chromonema structure with uniform distribution. 2) The first sign of the visible change in nuclear structure in the meiotic prophase is a disturbance in uniformity of the structure taking place gradually in the nucleus. The coiled aspect of the chromonemata becomes then more and more conspicuous, and the whole chromosomes can be traced for some considerable length. 3) The disturbance in the uniformity of the nuclear structure is due to the contraction or condensation of the chromosomes which are previously in the diffuse state. At the maximum condensation, the chromosomal bodies are distinguishable clearly from one another, the interchromosomal clear spaces being distinct, though a certain complication prevents us from the exact counting of their number. This stage correspond with the stage known as the “spiral stage” in somatic mitosis. 4) The condensed chromosomes are unravelled and the fine leptotene threads come out of them. The unravelling takes place without showing any marked change in the thickness of the chromonema threads in striking contrast to the case of the somatic mitosis where the threads become remarkably thicker than before unravelling. 5) The “Ansammlung der Chromatinkörner” seen in older literature seems to correspond with the chromosome condensation which we understand as the first stage observable distinctly in meiosis. The writer wishes to acknowledge his sincere gratitude to Prof. Y. KUWADA for his kind guidance and encouragement throughout the course of the present investigation.
1) In Tradescontia and Psilotum, results are obtained which indicate that the base of the bouquet corresponds with the distal region of the chromosomes, if there takes place no rotation of the nucleus before the bouquet formation. 2) In Psilotum, it is shown by the deplasmolysis experiments, that the part of the nuclear membrane at the base of the bouquet is physically weaker than the other parts of the membrane. 3) In Trillium, it is frequently observed that the bouquet figure is like a group of cytasters. 4) It is suggested that the bouquet arrangement of the chromosome threads originates in the chromosome arrangement in the preceding telophase, and that in the presentation of the pronounced polarized appearance of the bouquet certain conditions or phenomena such as the differential structure of the nuclear membrane or the fusion of the nucleoli are concerned, in association with the change in water relation in the nucleus in prophase. The present investigation was carried out under the direction of Prof. KUWADA to whom the author wishes to take this opportunity of expressing his sincere thanks. The author's thanks are also due to Dr. SINKE who helped the author much in various ways.
1) Der Bastard Ae. caudata L. (n=7)×Ae. cylindrica HOST (n=14) hat 7II+7I bei der Reifungsteilung der PMZ. Das gemeinsame Genom beider Arten ist C, weil mit der Dinkelreihe von Triticum (ABD) Ae. caudata kein homologes Genom hat, während Ae. cylindrica ein homologes (D) aufweist. 2) Die Beobachtungen bei der Rückkreuzung F1×Ae. caudata haben folgendes ergeben. Das Caudata-Genom (Ccaud) ist völlig austauschbar mit dem Ccyl-Genom von Ae. cylindrica. Die Rekombination zwischen beiden Genomen hat keinen Einfluß auf die Fruchtbarkeit. Auch die morphologischen Eigenschaften lassen einfach die MENDELsche Vererbung erkennen, was auf der Rekombination der betreffenden Chromosomen beruht. 3) Auf Grund der Rückkreuzung F1×Ae. cylindrica war eine Pflanze 27-chromosomig. Die Erklärung für die Chromosomenzahlschwankung bei den Folgegenerationen dieser Pflanze wurde gerade oben gegeben, wonach these Schwankung eben auf der reziproken Translokation zwischen 2 Chromosomen des F1-Bastards beruht. Diese Translokation kann entweder zwischen 2 Chromosomen des gleichen Genoms (C oder D) oder zwischen dem C- and D-Chromosom stattfinden. Zum Schluß möchten wir hinzufügen, daß wir der Japanischen Gesellschaft zur Förderung der Zytologie für die gewährte finanzielle Unterstützung zur Ausführun.g dieser Arbeit zu großem Dank verpflichtet sind.
1. The number of bivalents and univalents at the I. metaphase of PMC in 2725 POJ, 2722 POJ, 2878 POJ, 2883 POJ and 2364 POJ has been examined (Table 2). 2. Both 2725 POJ and 2722 POJ have one fragment each. These two fragments have perhaps the same origin, as the two varieties have been derived from the same cross (2364 POJ×EK 28). 3. In some preparations of 2878 POJ, it has been observed that 2-5 bivalents are closely arranged, showing so-called secondary associations. 4. S. spootaneum L. alas Karenko, which has been collected at Karenko, East Formosa, shows 48II at the I. metaphase of PMC.
1. A fertile diplosporophyte derived from a haplosporophyte by bud-variation was separated as a clone from the mother stock. The root tip cells in the mother stock had 12 chromosomes and those in the fertile diplosporophyte had the doubled chromosome complement. 2. There appeared several culms on which the panicles had fei tle grains mixed with some abortive flowers. Some adventitious roots from such culms consisted of haploid cells only, but others had completely diploid cells, and in other cases the root showed the constitution of a sectorial chimera of haploid and diploid tissue in longitudinal rows. A comparison in the sizes of the cells and the thickness of these roots was made and it was concluded that the sizes of the cells in respective tissue are firstly determined by the chromosome complements, but the propagation of the cells in the respective tissue is much influenced by other factors. The ratio of the cell volume of the haploid cells to that of the diploid cells is ca. 1:1.26 which is very near to 3√2, in other words the 2x-cells have about 2 times the volume of 1x-cells. 3. As the cause of the bud variation in the present case an over-heating of the water of the culture pot in the sprouting period is suggested. The 2x-sporophytes propagate more rapidly and grow more vigorously than 1x-sporophyte and overhelm the latter. So we can easily see that in nature haplosporophytes produced in some perennial plant, may survive until when the 2x-bud variation appeared among them, an event which proved fatal to the 1x-plants. 4. In early period of the mitosis, probably all the chromosomes are attached to the nucleolus either with their special points or with their end. The former are the naked or very thinly covered parts of the chromonemata, and not the surface of the hyalonema (the chromosome matrix). The nucleolar substance is probably concerned in the various stages of the chromosome cycle for all chromosomes, and not limited to particular ones such as the nucleolar or SAT-chromosomes. The latter kinds of chromosomes have longer naked or thinly covered chromonema neck, so that they are attached snore closely to the nucleolus. Here the writer wishes to express her thanks to Prof. K. Fujii for his kind advice in the course of this investigation. Her thanks are also due to the authorities of the Konosu Branch of the Imp. Agric. Exper. Station for the supply of the material.
1. The development of Plasmnodbou praecox in Cnlex pipiens pallens from 3 days to 17 days after feeding on the blood of infected canaries was studied cyto-histologically. 2. Normal ookinetes remained in the stomach of C. pipiens pallens until 11 days after feeding, but degenerating ookinetes were observed on the 17th day after feeding. 3. The formation of young oocysts of the parasites was observed within the stomach, but further development could not take place. 4. The development of P praecox in C. pipiens pallens is a matter of degree, namely, four types of development were observed in the individual mosquito of this species. 5. It was suggested that C. pipiens pallens has two races or two groups of individuals of the same race with regard to immunity from infection with P. praecox. In conclusion, the writer wishes to thank Prof. H. Kikuchi of the Japanese Army Medical College, Tokyo, for his kindness and help in facilitating the present work.
1. According to the condition of the health, the bulbs of Allium cepa are classified in three groups: A, B and C. Those belonging to class A are most healthy, and show the normal concave and convex plasmolysis. Those of class C are most unhealthy and apt to show the tonoplast plasmolysis. Those of class B occupy intermediate situations in these respects. 2. The tonoplast plasmolysis, which appears in Allium cepa, is classified according to its etiology. Generally the occurrence of the plasmolysis of this form is fundamentally due to the fact that the intrability of the cytoplasm increases, while the semipermeability of the tonoplast is maintained unaltered. The increased adhesion between the cytoplasm and cell membrane further facilitates its occurrence. 3. There are at least three ways through which cap plasmolysis results. The characteristics of the protuberance are described in detail and its relation to the cap formation is discussed. 4. Successive stages in the plasmolysis in Allium cepa, caused with saccharose, KCl and CaCl2 solution, are followed extending through several hours. The plasmolysis proceeds differently according to the kinds of the plasmolyticum as well as to the conditions of the material. 5. A preliminary water immersion of the material influences the plasmolysis form. In Allium cepa this influence is not so remark-able in the case of the healthy material as in the case of the unhealthy one, The tonoplast plasmolysis, which is very common to occur in the unhealthy material in a KCI solution is easily avoidable by the immersion in tap water for a length of time, even so short as 30 seconds, which gives rise to the increase of the frequency of concave plasmolysis. 6. In Rhoeo discolor the influence of the water immersion, contrary to that observed in Allium cepa, increases the occurrence of the concave plasmolysis in a saccharose solution. 7. In Allium cepa and Helodea denasa, the drying of tissue makes the plasmolytic separation difficult, and facilitates the occurrence of the tonoplast plasmolysis. A subsequent water immersion is effective in avoiding this abnormal tendency of the plasmolysis. In Rhoeo discolor a contrary result is obtained also in this respect and the drying increases the convex plasmolysis. 8. The cells of the ligule or auricule in Oryza sativa are plasmolyzed with a 0, 5 mol KCl solution. The paddy rice has the tendency to show concave plasmolysis and the upland rice convex plasmolysis. The soil moisture shows a quick and remarkable influence on the plasmolysis form of these cells. When the soil is dry, the concave plasmolysis increases and the plasmolytic separation is rendered difficult. The same tendency appears also after the plant is in the ear. 9. The subepidermal cells of the hypocotyl of Linum usitatissimum (flax) are plasmolyzed with a 0, 5 mol saccharose solution. The variety Minami, which is resistant to the wilt disease caused by Fusarium Lini, shows a more remarkable tendency to convex plasmolysis in comparison with several susceptible varieties, including the variety Riga from which the variety Minami has originated. 10. Also in the case of the flax the same relation between the soil moisture and the plasmolysis form is perceivable as in the rice plant. By a sufficient water supply the normal convex plasmolysis is recovered from the tendencies toward difficult plasmolytic separation and toward concave plasmolysis which are caused by the drying of the soil. 11. In the flax seedling the frequency of concave plasmolysis increases according to the age. A remarkable difference is visible even in a disparity of only a few days in age. 12. Among the strains of wheat a difference of the tendency of the plasmolysis form is visible.
A cytological study of Benzoin aestivale revealed the presence of several deviations from the usual meiotic process during microsporogenesis. These irregularities were considered to be diagnostic of previous hybridization of the species. The principal abnormality involved one of the twelve haploid chromosomes which appeared to be heteromorphic in both size and shape. In approximately half of the PMCs the larger of the heterochromosome elements was extruded from the heterotypic spindle and allowed to degenerate in the cytoplasm. As a result of the unequal distribution of the elements of the heterochromosome approximately two thirds of the functional pollen grains were calculated to carry the smaller element of the hetero-chromosome complex. The absence of a satisfactory degree of regularity seemed to exclude this case as being another X-Y sex chromosome mechanism. The meiotic behavior of the heterochromosome did suggest that it may represent an intermediate stage in the evolution of what are conventionally called sex chromosomes.