Abstract
The form and behaviour of the chromosomes at diakinesis in triploid tulips is quantitatively analysed. The assumptions are made, that (i) metaphase pairing of chromosomes is conditioned by chiasma formation in the chromosomes paired at pachytene and (ii) that only two of the three chromosomes pair at any one point in the triploid at pachytene. Variation in the behaviour of individual chromosomes (including the occurrence of univalents) in these triploids should then be the resultant of two kinds of variation earlier described, viz. (1) variation in the length of chromosomes paired at pachytene and (2) variation in the number of chiasmata formed in any constant length, such as may be calculated from the variation observed in chiasmata in whole configurations (bivalent or trivalent). The observed results agree closely with the expectation arrived at in this way (Graph IV) and thus verify the assumptions made on the grounds of earlier (qualitative) observations.
