Further Observations on the Inner Structure of the X-chromosome of Podisma sapporense (Orthoptera)

Abstract

1. The inner structure of the X-chromosome at first metaphase of the grasshopper, Podisma sapporense was described in this paper based on preparations which were obtained by the combined technique of the water-pretreatment procedure and paraffin method.
2. The number of gyres in the chromonema of the X-chromosome was found to be 5.5 exclusive of the kinetochore region. The direction of coiling was seen indefinite, and reversal of coiling was rarely observed.
3. The X-chromosome at first metaphase consists of two chromatids each of which is made up of two half-chromatids. Internally the X-chromosome comprises four chromonemata in its fundamental structure, and each one of the four chromonemata corresponds to a half-chromatid.
4. The kinetochore was found located at one end of each chromatid; it was observed as a tiny oblong or sometimes dumbbell-shaped body which connects with the chromonema by a fine thread.
5. The distal end of the X-chromosome is internally characterized by carrying a tiny compact granule which is similar to the kinetochore in appearance.