Mitosis and Meiosis

Abstract

FROM observations made in this laboratory by S. G. Smith, E. Marie Hearne, Jane D. Spier, J. M. Armstrong, A. W. S. Hunter, and me on meiosis and both haploid and diploid mitosis in Trillium, Matthiola, a number of cereals and grasses, and in grasshoppers, it can be shown that, at all stages of mitosis and meiosis, chromosome threads are attracted in pairs and that pairs of pairs are repulsed. A unified theory of chromosome behaviour thereby arises which seems adequately to explain the mechanism of both mitosis and meiosis, including the varied behaviour of univalents in the latter. Fig. 1 illustrates essential features, broken lines indicating stages during which splitting of the chromosomes can be seen to be occurring. (Through-out this note it is “effective” lateral splitting which is referred to if Nebel's, unpublished, observations in Tradescantia reflexa are confirmed for other material the initiation of the split occurs one division cycle earlier.)