1. Sterigma is always uninueleate. 2. The modus of caryokinesis in the sterigma is equational or vegetative, so that it is ascertained an a cytological basis that the conidiophore is actually an asexually reproducing organ. 3. The chromosomes and also the centrosome in the resting stage seem to be stored in a caryosome. At the beginning of mitosis, they escape from the latter, and take their respectively independent parts in the caryokinesis. 4. The spindle is of intranuelear origin, a centrosome being easily discernible at each pole. 5. Except this intranuclear origin of the spindle, the process of mitosis goes an regularly according to the well known scheme of somatic mitosis in higher organisms. 6. As the result of mitosis, two daughter nuclei are formed, and the apical one migrates through the narrow neck into the swelling pre-pared at the apex of the sterigma. Successive nuclear divisions take place in the lower nucleus, and the conidiospores are formed, arranging themselves in chains in the brush-like conidiophore. 7. The chromosomes are very small and round in shape, consider-able differences between them in size and form being scarcely observed. The haploid chromosome number (n) is found to be 2 in the following species examined:
1. Different methods of fixing root tips and Pollen mother cell smears of peas are described and discussed. 2. Formalin appears to render some of the nucleolar material and the matrix substance of somatic and meiotic chromosomes soluble in water, or to fail to render them insoluble as do chromic-fatty acid-formalin fixatives. 3. Alcohol appears to dissolve the meiotic chromosome matrix or to render it achromatic. 4. An intimate relationship between, and possible identity of nucleolar material and the matrix substance of somatic chromosomes is established. 5. The metotic and meiotic ehromosomes are described. The characters of each of the seven 'pairs permit identification of the individual members of the complement. They are as follows: 6. The chromonemata of the first meiotic metaphase and the chromosomes of later stages are found to show the Same individual characteristics as the somatic chromosomes.
Der Sauerstoffverbrauch des Lungengewebes an verschiedenen Schnitten wurde nach der alten WARBURG'schen Methode gemessen. 1) In der Sauerstoff-RINGERlösung ohne Traubenzucker war der Sauerstoffverbrauch geringer an der dünnen Schnitte als an der dicken, und die zeitliche Abnahme an der ersteren größer als an der letzteren. Der Sauerstoffverbrauch an der groben Masse war in der ersten Stunde etwa gleich demselben an der dicken Schnitte, aber die Abnahme des Verbrauches war in dem späteren Versuchsstadium geringer an der ersteren als an der letzteren. 2) In dem Sauerstoffgasmedium ohne RINGERlösung nahm der Sauerstoffverbrauch an beiden, der dünnen und der dicken Schnitte, einen etwa identischen Verlauf mit geringerem Unterschied in der Atmungsgröße. Der Verbrauch in der ersten halben Stunde war bedeutend größer. 3) In der Sauerstoff-RINGERlösung mit Traubenzucker war der Sauerstoffverbrauch an der dicken Schnitte während der ganzen Versuchszeit größer als an der dünnen, und seine zeitliche Abnahme war geringer als diejenige in der RINGERlösung ohne Traubenzucker, besonders an der dicken Schnitte.
1. A detailed account is given of the behaviour of the chromosomes from diplotene to second anaphase in Dahlia Merckii (2n=36), D. coccinea (2n=32), D. coronata (2n=32) and D. variabilis (2n=64). 2. Two kinds of chromosome association are found in these species: a) Primary Association, arising from particulate pairing at zygotene and determining segregation at metaphase. b) Secondary Association, arising at pro-metaphase and due to the general affinity of homologous chromosomes. This does not affect segregation. The chromosomes first associate at pro-metaphase when they are in close proximity to each other. 3. As first described by DARLINGTON, the primary association of chromosomes at metaphase is shown to be solely due to the mainten-ance of chiasmata formed at pachytene. Only those chromosome pairs or multivalents which are materially connected by chiasmata survive the strong repulsion phase of diakinesis. This repulsion results in the radial dispersion of the bivalents to the periphery of the nucleus, coupled with an equal aversion between the pairs and the members of each pair. The repulsion is fully maintained until mid-diaknesis, and then gradually diminishes to pro-metaphase, when the close proximity and general affinity of homologous chromosome results in groups of secondarily associated chromosomes at metaphase. The frequency and size of the group is characteristic for a given species. The importance of the diakinetic Phase in differentiating primary and secondary association is emphasised. 4. The theory of secondary association is discussed and evidence from the literature presented. It is claimed that secondary association is evidence of more remote affinities than can ever be expressed in primary association in a poly-ploid. This is proved by the occurrence of true (primary) association in triploid Pyrus between chromosomes which only show secondary association in the diploid form. 5. The effects of fixation, the correlation between allopolyploidy and secondary association and finally the value of secondary association as a criterion of homology are discussed.
1. For the fixation of metaphase chromosomes in all cell generations CHAMPY's mitochondrial fixative, concentrated 1.5 time as strong as the original, is found to be the most adequate one. 2. The basal chromosome number of the male of Eumeces latiscutatus is 26. The spermatogonial chromosomes can be sorted into two categories, macro- and micro-chromosomes. The macro-chromosomes are 12 V-shaped ones and the micro-chromosomes are 14 short rodand dot-like chromosomes. 3. Through maturation divisions every resultant spermatid contains a haploid set of chromosomes which consists of 6 V-sphaped and 7 dot-like ones. 4. The 12 V-shaped macro-chromosomes of this lizard probably correspond to macro-chromosomes of other members of the family Scincidae, e. g. Seincus officinalis and Chalcides tridactylus, but as to the relation between the 14 micro-chromosomes of the former and the 12 micro-chromosomes of the latter, nothing can be said definitely. 5. The sex-chromosomes of this lizard are two short rod-like ones. Between the members of the sex-chromosomes there is no differente by which one can distinguish the one as X and the other as Y. Consequently, this lizard has sex-chromosomes of an isomorphic type. 6. If we substitute X for the sex-chromosome the chromosome complex of the male may be formulated as 24+X+X=26.
1. Pollen mother-cell in bud of an artificially raised interspecific F1 plant of Papaver somniferum and P. orientale (“F1Papaver s×o I”) showed peculiar behaviour during their meiosis and the pollen-tetrad formation. 2. After the first division of meiosis, several unusual types of cytokinesis, enumerated below, occurred in one and the saure anther, in addition to the usual interphase of P. M. C. where middle lamella initial (MLI) at the equator of the ist spindle is ephemeral: 1) the MLI persists through interphase and the 2nd division of meiosis, but no cleavage furrows appeared during the interphase; 2) MLI persists and the cleavage furrows appeared an both sides of the MLI, and their formation proceeded centripetally, beginning from the periphery of P. M. C. and followed by the protrusion of callose wall from the mother-cell wall; 3) the cleavage formation does not start all around the cell as in Gase 3) (ef. p. 408), but from one side ; in this rase the cell division was not generally complete; 4) two daughter nuclei are connected by a bridge formed as a result of the incomplete nuclear division; as a con-sequence, the P. M. C. is constricted, the notch of the constriction being fiiled with the callose membrane; 5) two daughter groups of divided chromosomes form a reconstruction nucleus, MLI and cleavage furrows do or do not appear. By the test with a corallin soda solution, the MLI reacts like the P.M.C. wall and indicates a callose nature; but the colour reaction is decidedly more intensive in MLI, when compared with that of the P. M. C. wall. MLI and P.M.C. wall do not fuse, although they come in contact with each other. The MLI-granules first appear as fine granules at the center of the equatorial plane of the spindle between the connecting fibers, and the depositing proceeds towards the peri-phery of the P. M. C.. When the ist MLI finally reaches the inner surface of the P. M. C. wall, it persists during the 2nd division; when the MLI does not reach the P. M. C. wall, it is probable that it dissolves before the interphase sets in, because the writer failed to find it in such an interphase, unlike the rase observed by JUEL in Hemerocallis. The thickness of the callose protrusion varied in different P. M. C., which certainly leave plasmodesmic connections between the daughter cells through the MLI and the callose lamella. 3. In these P.M.C., the 2nd meiotic division occurs, so that suc-cessive as well as simultaneous pollen-tetrad formation, and also dyad and triad formations, were observed in one and the saure anther. From the above facts, it may be suggested that the saure gene or genes are responsible for the expression of these characters, at least in the present Gases, various modes of cytokinesis being modifications due to external influence. 4. The persistente of the MLI and the cleavage formation, fol-lowed by the formation of callose protrusion after the ist meiotic division in P. M. C. of “F1Papaver s×o” might have been caused by the delay of the 2nd division, i.e. Prolongation of the period of inter-phase probably due to an unusually low temperature. If such were really the Gase, an important factor in determining these characters would be the length of interval between the ist and 2nd divisions of meiosis. 5. The MLI formation and its relation to the formation of the callose protrusion were traced in the ist and 2nd divisions of meiosis in P. M. C. of Allium odorum and in the 2nd meiotic division of P. M. C. of Crepis virens, and it was aseertained in these plants and in P. M. C. in “F1Papaver s×o I” that the cleavage furrows always appeared along both sides of the MLI.