1. The diploid number of ehromosomes in Dasyurus viverrinus is 14, or 12+XY, in the male. 2. The sex chromosomes form a karyosome during the prophase of the first meiotic division. At metaphase they are associated terminally and the first division is always reductional. 3. The frequency and distribution of chiasmata in various bivalents have been analysed. In the autosomes chiasmata are distributed at random, with a frequency proportional to length. 4. There is a slight but possibly significant reduction in chiasma frequency at metaphase.
F1 hybrids between wheat and rye are completely male-sterile and so nearly female-sterile that artificial backcrossing is nearly fruitless. With open pollination less than 0.02 per cent of the fully developed flowers set seed. All F1 eggs which functioned resulted from a process of restitution which was observed at both meiotic divisions of F1 During the process both the loss and duplication of chromosomes may occur so that the number in functioning eggs may vary slightly above or below the somatic number 28 (21 wheat+7 rye), and the genic content may be quite variable. The second generation feil into 3 fairly equal groups with approximately 28, 42, and 49 chromosomes respectively. Both the chromosome behaviour and the genetical characters indicate that the 28-chromosome group originated through parthenogenetic development of F1 restituted eggs. In both respeets they are similar to F1, with such exceptions as would be due to the loss or duplication of chromosomes at restitution. Their occurrence supports the theory that amphidiploids may be due to parthenogenetic development of restituted eggs followed by chromosome doubling. Plants of the 42-chromosome group had only about 14 pairs at meiosis, exhibited characters of emmer wheats, and were very sterile. It is believed that they originated through the fertilization of restituted eggs by sperms from pure 14-chromosome (emmer) wheats. They had a genom from each of T. vulgare, an emmer, and rye. Plants of the 49-chromosome group had about 21 pairs at meiosis, exhibited chiefly vulgare wheat characters, and were much more fertile. They originated through fertilization of restituted eggs by sperms from 21-chromosome wheat. A prolonged effort was made to establish, among the descendants of the 49-chromosome group, lines with more than 21 pairs and with rye characters. Although a considerable number of plants with 22 or more pairs were identified, it was impossible to make the condition constant. Similarly, although different rye characters were retained for many generations by selection, it was impossible to secure true-breeding lines with rye characters. Characters somewhat resembling certain ones of rye were established in a few lines but were shown to be due to out-crossing to emmers during the early sterile generations. No evidence could be found that individual rye chromosomes can be added permanently to the wheat complement, or substituted for wheat chromosomes, nor that by crossing-over or translocation composite wheat-rye chromosomes can be produced or at least can cause a visible effect. Special features described and discussed are: chromosome doubiing in one-quarter of one Pollen sac without producing quadrivalents; secondary pairing; and a haploid plant.
1. The prophase chromosomes in the pollen grains of Hyacinthus orientalis var. “Sir William Mansfield” (2x=16) show relie and relational coiling. 2. These kinds of coiling may be in the same or in opposite directions in the two arms, but the direction is generally consistent within an arm. 3. In the nucleolar chromosome there is no evidence of a particular direction characteristic of either arm, but there is a slight positive correlation between the directions of relie coiling in opposite arms. The relational coiling in the two arms appears to be at random with respect to one another. 4. If relic coiling is determined by the internal coils at the previous mitosis and relational coiling to those developing at the present mitosis, then the coiling directions in successive mitoses seem to be indeterminate, and characteristic of individual mitoses, but not of individual chromosomes.
All the species of Peromyscus so far studied except P. eremicus have 48 chromosomes. One subspecies of P maniculatus was found with 52 chromosomes. Evidence is found supporting Painter's base number 48 for mammals, but no explanation is offered for the 58 chromosomes found in P eremicus. Evidence is found in favor of fragmentation as a method for increasing chromosome numbers within a species. This process may be in progress in P maniculatus at the present time. Almost complete harmony is found between the results of the breeding tests made by Dice and the results of the cytological study made here. A suggested relationship between various species of Peromyscus is offered based upon cytological evidence.
Germinated seeds from Vicia Faba, Nicotiana Langsdorffii, F1 (N. rustica×N. tabacum), Crepis capillaris, and Pisum sativum, were centrifuged several days with interruptions in electrie centrifuge at 1500 to 4000 revolutions per minute. A stratification of the cell content occurred following centrifuging in the following order: Starch and plastids always get situated an the centrifugal cell wall, nuclei occupied most frequently centrifugal position, but in a few instances in some small tissue regions, they were found about in the middle of the cells or even at the centripetal cell wall. Nucleoli tend to occupy the centrifugal side in the nuclei (or the nuclei get turned this way). Chondriosomes tend to occupy centrifugal position in the cytoplasm, while the vacuoles the centripetal ones. Some cells died as a result of centrifuging. The achromatic figures (spindles) in the root tips of Vicia Faba were much more deformed during the early metaphase, metaphase, and early anaphase than during the late anaphase and telophase. Cenrtifuging interfers with the mitotic processes. Failure of chromosome separation and cell division as well as the transfer of single chromosomes during the early metaphase which have been directed to one of the poles in the group of these directed to the other pole lead to formation of monosomic, trisomie, polysomic tetraploid, etc. cells. Injured achromatic figures may also lead to such abnormalities. Chromosomes with dislocated segments are occasionally formed following centrifuging (Crepis capillaris). Various kinds of ehromosomal chimeras were found in the root tips. An amphidiploid shoot was formed by a centrifuged N. rustica×N. tabacunm hybrid. A semisterile plant and a variegated one (with chlorophyll deficiency) were produced from centrifuged Nicotiana Langsdorffii plant. Morphological abnormalities (narrow or broad leaves, crinkled, etc.) were induced in centrifuged Pisum sativum.
1. A species, Fritillaria chitralensis, has been found in which the two longer median chromosomes are distinguishable from one another and from the remainder of the complement at meiosis. 2. In general, chiasmata are freely distributed along the length of the chromosomes, but in some bivalents intermittent pairing is found. 3. Interlocking of bivalents is fairly frequent and one case of double interlocking was observed. 4. The average chiasma frequency per bivalent is found to be lower in the M bivalents than in the SM or sub-terminal bivalents. 5. The curves of chiasma frequency of M and SM bivalents show a bi-modality not previously observed in any chromosomes. 6. Two factors conditioning variance in chiasma frequency are postulated: (a) The degree of completeness of pachytene pairing, (b) The frequency of chiasma formation per unit of length paired. 7. It is suggested that approach of the centromere to a terminal position facilitates pachytene pairing and chiasma formation. 8. Chromatid bridges and acentric fragments observed at first and second anaphase indicate the presence of relatively inverted segments in 7 of the 12 chromosomes of this species.
The derivation of the theory of “cyto-nuclear harmony” is outlined as substantiated by the following evidence. A. The evidence of known hybrids. B. The evidence of species indicating a hybrid ancestry. C. The evidence of diploid parthenogenesis. D. The evidence of chromosome duplication. E. The evidence of special Gases including…, 1. Haploid parthenogenesis. 2. Gametophytic generations. A number of otherwise common but insignificant observations are shown to take an importance in view of the theory of “cytonuclear harmony” and yield profitable lins of investigation for a better understanding of the morphology of the dividing cell.
1. The ehromosomes in the epithelial cells of larval salamanders were prepared for study by the use of the smear method. Both acetocarmine and permanent smears were used. 2. The chromosomes of Ainblystoma punctatum consist of a matrix in which lies a coiled or zigzag thread. The thread is double at all stages except metaphase when it is quadruple. 3. In occasional cells the chromatids are widely separated during prophase and metaphase. A possible explanation for this condition is suggested.
1) Die in der vorliegenden Forschung festgestellten Karyotypen sind wie folgend: 2n Verdoppelte Zahl Cephalanthera faleata Bl.……….6L+28s=34 12L+56s=68 C. erecta Bl.i………………… 6L+28s=34 C. Shizuowi F. Maekawa………….6L+26s=32 12L+52s=64 Epipactis Thunbergii A. Gray…….6L+34s=40 E. Sayekiana Makino………….6L+2Lt+32s=40 12L+4Lt+64s=80 2) In allen untersuchten Wurzeln von C. Shizuoi und E. Sayehiana, wurden die Mixoploidie beobachtet und in verschiedenen Teilen der Wurzel nämlich in Karyptra, Karyptrogen, Dermatogen, Periblem, Plerom und in der Streckungszone, tetraploide Zellen gefunden. 3) Die Prozesse der Entstehung der tetraploiden Zellen war wie folgt festgestellt: a) Nach der Kernteilung entsteht keine Membran zwischen den Tochterkernen, später aber vereinigen sich beide Tochterkerne (Tabelle 1, a). b) Nach der Kernteilung entsteht eine Zellwand, aber nicht vollkommen. Eine Vereinigung der Tochterkerne durch die Lücke der Zellwand wurde nicht beobachtet (Tabelle 1, b). c) Beide Tochterchromosomen, besonders lange Chromosomen, haben zu kurze Entfernung um sich voneinander zu trennen, da die Richtung der meisten Kernteilungen parallel zu der kurzen Achse der auffallend flachen Zelle verläuft. Infolgedessen vereinigen sich beide Gruppen der Tochterchromosomen (Tabelle 2, a). 4) Als Merkmal um die diploiden und tetraploiden Zellen in ruhenden Zustand zu beurteilen, wurden die Zahlen der Nukleolen zusammen mit anderen Kriterien benutzt. 5) Bei Epipactis wurde das Gebiet der tetraploiden Zellen in Dermatogen von der Wurzelhaube bis zur Streckungszone, in einer Ausdehnung von 1350 Mikron, das heißt in 90 Querschnitten zu je 15 Mikron Dicke, verfolgt. Dadurch wurde gefunden, daß bei Epipactis die Teilungsperiode der tetraploiden Zellen beinahe gleich der der diploiden Zellen ist; und wenn eine tetraploide Zelle im Wurzelgewebe einmal entsteht, so vermehrt sie sich mit dem Wachstum der Wurzel zu einer bestimmten Zahl und verschwindet nie. Zum Schluß sei mir gestattet, meinem hochverehrten Lehrer Herrn Dr. Y. SINOTô nach dessen wohlwollendem Vorschlag ich diese Forschung machte, an dieser Stelle meinen verbindlichsten Dank auszusprechen. Desgleichen bin ich Herrn Dr. F. MAEKAWA, der mir bei dieser Arbeit im taxonomischen Gebiet gütigst behilflich war zu großem Dank verpflichtet.
In the present work, three types of Scirpus lacustris L., i.e. normal self-colored typicus and two variegated forms pictus and zebrinus have been studied. The chromosome numbers of these three forms are determined as follows: (1) normal form typiczts, n=19, 2n=38, ineluding one large chromosome in the polten mother cells and two in the somatic cells; (2) variegated form pictus, 2n=40, ineluding one large chromosome in the somatic cells; (3) variegated form zebrinus, 2n=42, ineluding no such large element as found in the other two forms. Assuming that the two variegated forms were derived from the normal green form, the relation between the chromosome numbers of the three forms, especially the existence of the so-called “Sammelchromosom”, has been discussed from the point of segmentation, and the correlation between the chromosomal conditions and variegation has also been considered. The writer wishes to record his cordial thanks to Dr. Honda for his kindness in verifying the plants used in the present work. Thanks are also due to Dr. Sinotô under whose direction the work has been carried out.
Earlier measurements of the surface behavior of cleaving seaurchin eggs (Mespilia globulus) haue been repeated an sand-dollar (Astrielypeus manni) eggs, extending through the second cleavage. The following points have been established. 1. The surface behavior of cleaving sand-dollar eggs is essentially similar, qualitatively and quantitatively, to that of sea-urchin eggs. 2. The thin hyaline plasma layer of Astrielypeius eggs does not mask the behavior of the endoplasmic surface as does the thick hyaline plasma layer of Mespilia eggs. 3. No difference can be detected between the surface behavior of the eggs at the animal pole, vegetal pole and equatorial region. 4. It is found from the distribution of particles that until the completion of cleavage, the original egg surface is stretched to cover the blastomeres. In eggs in calcium-free medium during interkinesis, a particle-free area appears in the furrow region, the extent of which corresponds numerically to the contact surface between the blastomeres in normal sea water. From these facts it is concluded that a new formation of surface takes place in the furrow region after cleavage has been completed, and further, that the contact area between the blastomeres in normal eggs is composed of this newly formed surface.
1) The behaviour of the cytoplasmic sheath of the generative cell has been investigated in the pollen tube of Crinum and Hippeastrum in the living state, occasionally with the help of either vital staining or fixation and staining. 2) The sheath contains “droplets”, which gather in a spindle-shape around the generative nucleus or each of the two sperm nuclei formed, and no stable membrane is present around the sheath. 3) In Crinum, the karyokinesis of the generative nucleus has not been immediately followed by a normal cytokinesis, but only by a “false” one. 4) Successive observations on the sperm cells in the pollen tube of Hippeastrum showed that the cytoplasmic sheath could be easily stripped from the nucleus by an external force at the point of death.
The prochromosome and chromosome cycle has been traced in the somatic divisions of Polanisia traclzyspermna (2n=20). Prochromosomes are derived directly from the telophase chromosomes by the persistence of the chromatic material in the attachment constriction region. Fibres are not apparent in the resting nuclei of Polanisia, while they are comparatively prominent in the telophases. Earlier stages of meiosis in Gynandropsis pentaphylla (n=17) are described. The fall diploid number of prochromosomes (34) is present in the telophase of the last premeiotic division, as also in the resting stage of the nucleus of the pollen mother cell, and the theory of the pairing of the prochromosomes in the premeiotic nucleus is not accepted. Chromonemata are reported in the chromosomes and evidence is submitted which suggests that the chromosome structure as well as the chromosome cycle in plants with prochromosomes are in essence the same as in plants without prochromosomes in both somatic and meiotic divisions. The nucleolus is organized in Polanisia by a pair of satellited chromosomes. A portion of the chromatin contained in the chromosomes is found to be accumulated an the surface of this primary nucleolus, whose surface consequently presents darkly stained patches from late telophase up to Tate prophase. The close association of the prochromosomes with the nucleolus at telophase and early prophase is explained an this basis. In conclusion, I have great pleasure in recording my gratitude to Professor R. Ruggles Gates, for suggesting this piece of work in connection with my work an the Capparidaceae and for helpful criticism and guidance.