Quarterly Journal of Microscopical Science, Vol s2-85, 107-116, Copyright © 1945 by Company of Biologists

Memoirs: The Meiotic Phase of Calandra oryzae

¹ Department of Zoology, University of Melbourne

1. The somatic chromosome number for the female of Calandra oryzae is twelve; for the male, eleven. The latter is presumably of XO composition.

2. In both sexes the haploid number of loosely paired threads is present at early diplotene. Upon condensation, the exconjugant chromosomes undergo a temporary complete dissociation into their univalent constituents, so that the diploid number of separate elements is reconstituted.

3. At the equatorial plate stage the twelve univalent chromosomes associate once again into six bivalents.

4. In the female this is followed by a precocious separation of the anaphase chromatids, so that by the conclusion of the first meiotic division the diploid number of chromosome elements is evident at both ends of the spindle. There is no comparable process during the course of spermatogenesis; at anaphase I the haploid set of chromosomes passes to each pole, the nuclei so produced entering a resting condition.

Note:

This work, carried out during the tenure of a Howitt Research Scholarship, was suggested and directed by Professor W. E. Agar to whom I should like to offer my sincere thanks. I also wish to express my indebtedness for the invaluable assistance given me by Associate Professor O. W. Tiegs.