1. The diploid number in Poophilus is 25, and the haploid number is 12AA and X. 2. The sex chromosome segregates in the first division typical of Homoptera Auchenorrhyncha. 3. The sex chromosome lags (succession) in the first division and not n the second meiotic division. A detailed behaviour of the same is discussed.
The concentration of Ca++ in the culture does influence the intake of Mg++ by the yeast cells. However there is an optimum concentration of Ca++ when maximum consumption of Mg++ is observed. The increase of Ca++ in the culture hinders the intake of PQ'''4 by the yeast cells when the concentration of Ca++ in the yeast culture is high, increased consumption of nitrogen is observed. The increase of Ca++ in the culture favours the intake of Ca++ by the yeast cells. The optimum concentration of Ca++ from the growth of yeast is 0.02% and it is interesting to note that under this optimum condition for the yeast growth, the intake of Ca++ Mg++ and PO'''4 remains very low and the consumption of nitrogen by the yeast cells remains least.
Cytomixis appears to be a natural phenomenon occurring in either mitosis or meiosis between pollen mother cells and other types of cells with thin walls that are joined by cytoplasmic bands. Any external or internal conditions which upset the mechanics of cell wall formation and the rate of division could be a possible cause of cytomixis by leaving cytoplasmic bands through which chromatin movement can occur. Cytomixis in Gossypiurn is thought to be responsible for three other types of abnormalities: binucleate cells, pollen mother cells with reduced or increased numbers of chromosomes and somatic loss of chromosomes.
1. The long chromosomes both in Cletus punctiger and Lanchnophorus singalensis possess active mobility at two points, terminal in the former and sub-terminal in the latter, during the gonial anaphase, while in both the meiotic divisions it is confined to one end only. This actively mobile end, in the meiotic anaphases, further differs from the remaining part of the chromosome by a different nature of the heterochromatin. 2. The structure of these long elements in all the four species, Cletus punctiger, Lanchnophorus singalensis, Aphanus sordidus and Dieuches sp., during the mitotic and meiotic prophases reveals that these elements have no region with a special cycle of division. 3. In spite of a close similarity of the chromosome form in Homoptera and Heteroptera it has been seen that the chromosomes in the latter differ markedly from those of coccids and aphids (Homoptera) where the diffused nature of the kinetochore has been established experimentally. 4. It has been suggested that the kinetic activity in Heteroptera resembles that of the T-chromosome of rye rather than a diffused one.
1. The karyotypes of three species of Gymnaster, five species of Kalimeris and three species of Heteropappus were studied by an oxyquinoline aceto-orcein technique. 2. The karyotypes of these genera are characterized by the presence of symmetrical chromosomes with median-submedian centromeres. 3. Chromosomes with secondary constrictions (L2E-chromosomes) were found with the exception of G. koraiensis. 4. Judging from their karyotypes, polyploid species of the genera Kalimeris and Heteropappus are considered to be allopolyploids. 5. Differences in karyotypes are sufficient to separate the section Homolepis from the section Crassifolium of the genus Gymnaster and the section Asteromoea from the section Cordifolium of the genus Kalimeris. However, the cytological similarity of the karyotypes of Gymnaster, Kalimeris and Heteropappus to the genus Aster is of such a degree that the former three genera could be regarded as sections of Aster.
Chromosome behavior in meiosis I was studied in six partially sterile hybrids between varieties of cultivated rice. Diakinesis and metaphase were normal in the sterile hybrids, with no evidence of translocations or absence of pairing to account for the sterility. In two of the hybrids chromosome bridges without fragments occurred at anaphase and telophase in a low but regular frequency. It was concluded that such bridges may be the result of delayed terminalization of chiasmata in pairs of chromosomes which are structurally different at some point. Although rice is not well suited to a study of pachytene and detailed analysis of chromosome pairing was not possible, figures which appeared to be chromosome loops typical of inversions were found in five of the seven hybrids. It was concluded that some evidence of structural differentiation in the parental chromosomes existed and that partial sterility in intervarietal hybrids of cultivated rice is probably due primarily to cryptic structural hybridity, possibly arising from included inversions.
1. Structures of pure cultured Euglena were studied with an optical and an electron microscope. A cytochemical test was carried out with the Feulgen and the pyronin-methyl green staining. 2. a. A chromonema in resting stage is composed of several thin threads, 10mμ in thickness. b. A chloroplast has many lamellae and usually one pyrenoid in which several lamellae are observed. c. In the mitochondria which reduce Janus green B, cristae mitochondriales are observed. d. A flagellum is composed of several threads running lengthwise. e. An eye spot is constructed with many spherical bodies. f. An endoplasmic reticulum seems to be constructed with complicated membranes or tubes g. On the cell surface there are many grooves surrounding the cell surface. 3. Chromosomal behaviors in mitotic cycle are similar to those in mitosis observed in higher plants. 4. Polynucleate cells, which seem to be somewhat abnormal, are observed sometimes. 5. The results of the cytochemical tests showed that the chromonemata contained DNA and the nucleoli contained RNA.
Chromosome counts and descriptions are given for some species of the genera Babiana, Geissorhiza and Romulea in the fridaceae. On the basi of three species of Babiana reported here and elsewhere, the basic number for the genus may be tentatively set at 6 or 7. From five species of Romulea so far reported, the basic number of the genus may be set at 9. A possible triploid species is reported. One species in the genus Geissorhiza reported here has a basic number of 13. Many other species of these genera and others in the Iridaceac remain to be investigated cytologically.
1. Comparative electron-microscopic studies have been carried out on three natural strains of Blepharisra undulans with special reference to the pigment granules occurring in the subpellicular layer. 2. The micrographs of sections of the deeply-pigmented Ni-1 strain animals show numerous spheroidal granulated granules, 0.5μ in diameter. 3. The colorless Na-white strain animals, on the other hand, possess no granulated granules, but show some irregular-shaped compact granules which are 0.2-0.4μ in diameter. 4. In the pink-colored Na strain animals, both types of granules are ound mixed in varying ratio. 5. The granulated granules and the compact granules in the electron micrographs seem to correspond respectively to the red and the colorless granules in the light microscope image. 6. The granules are distinct in nature from mitochondria, which occur underneath the layer of pigment granules in the ectoplasm.
The spermatogonial complement of the Cletus sp. is 17, and the mode of sex determination of this insect is XO: XX type. The chromosomes comprise of fourteen autosomes, a pair of m-chromosomes and an odd X-chromosome. The early diakinetic bivalents possess prominent lampbrush processes which persist to the end of diakinesis. These processes originate from the nucleoprotein matrix of the chromosomes and these form an integral part of the latter. Added in proof. The lampbrush formation in the chromosomes, it is contended (Sharma, G. P. and Ram Parshad, Nature, 180, p. 147, 1957), is bound up with depolymerisation of the nucleic acids, but it appears to be a mere speculation unsupported by any factual evidence, whatsoever.
The “mitochondrial fraction” isolated from young Skunk-cabbage (Symplocarpus foetidus) flowers was fixed with OsO4 and examined in the electron microscope. Particles which had been exposed briefly to water before fixation clearly showed an external membrane and an internal organization. Small granules, a larger dense body, and uniform filaments, approximately 35mμ wide, were seen within the particles. The possibility that these particles (mitochondria) are composed of an internal mass of interwoven filaments or tubules is considered.
1. The chromosome number in the males of Dicranocephalus agilis is 2n=14. The complement includes a pair of m-chromosomes and a pair of sub-equal sex chromosomes. 2. The first division of meiosis is reductional for the differential regions of the autosomes and for the m-chromosomes which are completely differential. It is equational with respect of the sex chromosomes. 3. The sex chromosomes are positively heteropycnotic at the prophase of meiosis I and are associated non-homologously. They are double when the autosomes pair at zygotene. 4. At metaphase of first and second division the autosomes congress to form a ring on the periphery of the spindle. This is in keeping with their size, valency and the space available. 5. At equilibrium, the sex chromosomes auto-orientate side by side in the ring with the autosomes at first metaphase. The sex pseudo-bivalent congresses in the centre of the spindle at second metaphase where less space is available. 6. The sex chromosomes become negatively heteropycnotic at first metaphase and the sex chromatids form a pseudo-bivalent during their anaphase separation. This is facilitated by their side by side orientation at metaphase (a consequence of their earlier association), their convergence as they approach the poles and their reduced repulsion. 7. The early formation of the sex pseudo-bivalednt in D. agilis and Oncopeltus fasciatus is considered adaptive in the absence of an interphase which suggests a more rapid division than in Cimex and Oncopeltus nigriceps where the pseudo-obivalent forms later and the second division is of longer duration. 8. The m-chromosomes are unpaired at prophase of the first division but associate in the centre of the spindle at first metaphase when they are understained. They congress to the centre of the spindle at second division also. They, and the sex chromosomes remain understained until the completion of meiosis. 9. The differential staining of the sex and in-chromosomes compared with the autosomes is important only in that it provides a visible demonstration of allocycly which can be inferred on other grounds. 10. The centromere in D. agilis is diffuse. It is suggested that the time and place at which the chromosomal spindle fibres are organised are partly responsible for determining whether the first division of meiosis is reductional for the differential segments (as is general in the Heteroptera) or equational (as is generally the case in the Homoptera).