Les photomicrographies qui ont suivis le processus du développement embryonnaire chez D. melanogaster ont été recordés; on en peat distinguer 16 stades. Les souches létaux embryonnaires chez Drosophila, dont les modes d' expression de la létalité ont été étudiés, ant été arrangées sur une liste; et de plus, les déscriptions sur la létalité des quelques mutants obtenus dans notre laboratoire ont été faits. On peut voir quelques crises ou périodes sesnsibles au cours du développement, lesquelles sont représentées principalement aux stades de la formation du blastoderme, de la différenciation des tissus mésodermique et endodermique, de la blastokinèse et de l' irruption du gaz dans la trachée.
Le blastoderme se forme dans les embryons dont le contenu a été stratifié par centrifugation au stade de contraction du cytoplasme. Dans le cas, la formation du blastoderme est commencée par la portion moyenne: la zone cytoplasmique contenant les noyaux, succedant son evolution en avant et en arrière d'embryon. Les cellules polaires n'ont pas été formées aux embryons centrifugés. L'insuccès de la formation de cettes cellules doit être le changement structural de la couche périphéral postérieure.
1. A critical cytological investigation of nine species of Ophioglossum (including several cytological and geographic races), one species of Botrychium and the monotypic Helminthostachys has been made. 2. The lowest haploid number for Ophioglossum is n=120 and for Helminthostachys, n=94. 3. Almost all the species of Ophioglossum investigated in the present study (excepting the aneuploid series in O. reticulatum and perhaps O. vulgatum) are found to form a polyploid series based on the haploid number n=120. 4. O. reticulatum L. is shown to have the highest chromosome number yet recorded in any species (n=c. 630, 2n=c. 1260). 5. The basic chromosome number of the Ophioglossaceae is postulated to be 15. 6. Evidences of chromosome numbers obtained from this study show the probability that there is some parallelism in the cytological evolution of the Ophioglossaceae and the Schizaeaceae. Both Ophioglossum and Schizaea exhibit very high chromosome numbers. The basic number 15, characteristic of the Ophioglossaceae, is also shared by Lygodium, the most primitive genus of the Schizaeaceae. 7. Cytological evidence is in favour of regarding Botrychium as the most primitive of the three genera while Helminthostachys is intermediate and Ophioglossum the most specialised. 8. There is no cytological support for the segregation of species of Botrychium and Ophioglossum into subgenera or for raising these subgenera to generic status. 9. It is suggested that the greater percentage of polyploids as well as higher grades of polyploidy encountered in South Indian races of Ophioglossum may be related to the fact that Peninsular India is geologically one of the oldest land masses with a continued vegetation cover for a very long geological period. This suggestion is incidentally supported by evidences of chromosome numbers from ancient genera like Tmesipteris and Phylloglossum from Australia which also represents a very old geological formation. 10. The taxonomic delimitation in species like O. reticulatum, O. petiolatum and O. vulgatum is seen to be very artificially drawn. 11. Taxonomic revision in the light of cytology is necessary for O. nudicaule.
1) It was shown with the aid of x-ray irradiation test that a) premeiotic mitosis in the anther of T. kamtschaticum is finished at the end of September, or about five months prior to MI in the PMCs, and b) chromosome splitting in meiotic prophase in the PMCs takes place in late October. 2) Sensitivity changes to x-rays during early meiotic prophase in the PMCs of this plant was investigated to show that the PMCs of the materials taken from Toyoni population became quite labile to the irradiation in mid October. The lability seems to concern, examined with the materials taken from Akkeshi population, with modifications of restitution process of the broken ends produced in chromosomes by the irradiations. 3) Four types of aberration: B'' (chromosome breakage), T'''' (chromosome translocation), T''' (chromosome-chromatid translocation) and T'' (chromatid translocation) were distinguished in bivalents at MI. The translocations increased in proportionate to two power of x-ray dosage, while the breakages were produced approximately in direct proportion to it. 4) The heteromorphic chromosome pairs induced by irradiation which was given before the prophase splitting of chromosomes in the PMCs, performed, in majority of the cases, reductional opening-out of chromatids at diplotene. 5) Configurations which were regarded by Matsuura as supporting equational opening-out of chromatids were extremely rare. It was suggested that these rare configurations may possibly be the ones derived from T''' and T'' which occurred between homologous chromosome arms. On the other hand configurations supporting the chiasma theory were often taken by the heteromorphic pairs.
The Golgi bodies in the neurones of the cerebral and visceral ganglia of a pelecypod, I Meretrix meretrix lusoria (Gemelin), were studied in the living condition with the phase optics and in ultra-thin sections by electron microscopy, by way of comparison with those demonstrated by the classical method. In Kolatchev preparations, the Golgi bodies appear as separated bodies in the form of a dot, rod or crescent. They correspond to the dictyosomes described by previous workers. They are particularly dense in occurrence in the cytoplasm around the nucleus and in the axon-hillock. Observations by phase contrast microscopy reveal that the Golgi bodies in the living neurones appear as round bodies, each having a dark ring- or crescent-shaped rim and a light center. They show a structure consisting of a cortex and a medulla which correspond to a dictyosome and an archoplasm, respectively. The dictyosomal portion of the Golgi bodies is stained with neutral red with some difficulty, while the archoplasm is inactive to the stain. The cytoplasm contains small granules or lipochondria which are distinctly and homogeneously stained with neutral red. Each of the Golgi bodies when examined under the electron microscope is found to be a complex consisting of paired membranes, vacuoles and granules or microvesicles. It is probable that the dictyosome is composed of a stack of paired membranes and that the archoplasm is an aggregation of vacuoles and microvesicles.
The present paper describes the results of a chromosomal analysis in tumor cells of a human mammary carcinoma. The material for study was derived by centrifuging from the pleural fluid from a patient. It was established that there is present at least a stemline of tumor cells which are characterized by a hypertriploid complex of chromosomes, primarily contributing to the neoplastic growth. A possible item of evidence has been presented that there may be an additional existence of tumor stem-cells with a hyperhexaploid complex.
1. A semi-asynaptic plant of Abelrnoschus esculentus (L.) Moens. has been reported and its morphology and cytology have been described. The plant showed luxuriant vegetative growth, produced a large number of flowers and fruits. It grew for a much longer time than normal plants. The normal looking fruits were, however, smaller than the fruits of normal ones and were completely empty. 2. On cytological examinations pollen mother cells showed complete or partial failure of the pairing of chromosomes at meiosis. The univalents generally divided into two chromatids at first anaphase. Inspite of these meiotic irregularities some normal looking pollen grains were found and they germinated on the stigma forming small pollen tubes, which indicates that pollen grains can presumably to some extent survive the loss of some genes. Perhaps this is due to polyploid nature of this plant. 3. Crossing experiments showed that no functional eggs were organised, hence the meiotic irregularities were presumably on the female side also. The formation of normal fruits was presumably due to the stimulus received from growth of pollen tubes through the style.
Studies were made in Eu-sorghum of the orientation of reciprocal translocation chromosomes, and of quadrivalents of hybrids and pure species tetraploids. In all cases segregation was directional and agrees with the hypothesis that if a species displays directed orientation of the chromosomes in an interchange complex at metaphase I, the quadrivalents in an autotetraploid of this species likewise will display directed orientation. But comparable studies in Gossypium hirsutum on the orientation of chromosomes at metaphase I in interchange complexes and in quadrivalents of an autoploid are at variance with the hypothesis. Some interchange chromosomes of G. hirsutum show directed segregation while others behave like the autoploid and do not show directed segregation. Limited data indicate that the type of configurion is determined at the time the centromeres begin repelling one another. The autoploid of G. hirsutum was the result of spontaneous doubling in a normal plant. Modes of association and chiasma frequency per chromosomes in the autoploid are presented. It is concluded that the chiasma frequency per chromosome in the amphidiploid G. hirsutum is between 1 and 1.5.
1) The effect of 2 methyl amino 1.3 diaza-azulene on the mitotic cells of Tradescantia was investigated in vivo by application of the agar plate method. 2) In concentrations higher than 5×10-3M, nuclei with doubled chromosome number are induced, when the cells are treated in prophase and prometaphase, while bi-nucleate cells are induced, when treated in metaphase. 3) In a range of 1×10-3 M concentration, the atractoplast is suppressed in its function when the cells are treated in pro-metaphase but can develop into phragmoplast substance. As results of combinations of these phenomena, multi-nucleate cells with multi-septa, appear in telophase. 4) From the results of these experiments, the abnormal behaviour of the mitosis is analysed into two steps: one is the suppression of the atractoplast, and the other, the deformation of the phragmoplast. Also, the relationship between the stage of mitosis at the beginning of the treatment and the types of abnormal mitosis is discussed.
The fine structure of the first metaphase spindle in pollen mother cells of Lilium longiflorum and Magnolia liliflora has been studied by means of the electron microscope. It has been confirmed that the treatment with CdCl2 solution was very efficacious for the preservation of the internal fine structure of the spindle. In ultra-thin sections it has been asserted that the atractoplast is composed of submicroscopic unit fibrils as the dispersed phase, and that a chromosomal fiber is a bundle consisting of many fine fibrils. The surface boundary of the spindle body was partly observed as membrane structure. The author is grateful to Professor B. Wada for advice and helpful suggestion, and to Dr. N. Tanaka and Mr. S. Sakata for valuable help with the experiments. This work was supported in part by a grant from the Science Research Fund of the Ministry of Education and in part by a grant from the Fuju-kai Research Encouragement Fund.