抄録
The present paper contains a description of the mode of chromatid disjunction at MI in the PMC of Trillium kamtschaticum which is displayed with unusual clearness. It was statistically studied by employing two different means: (i) by direct observations an the behavior of the daughter kinetochores of metaphase bivalents, and (ii) by inductions from observations an the direction of chromonema coiling within pairs of halfbivalents at anaphase. The results from both these are essentially in accordance with each other and indicate that: (i) there are three modes of chromatid disjunction for individual bivalents, (a) equational in both the arm pairs (EE), (b) equational in one arm pair but reductional in the other (ER), and (c) reductional in both the arm pairs (RR), (ii) the Proportion of EE:ER:RR is 4:4:1, and consequently. (iii) for individual arm pairs, E:R=2:1.
These results were explained by assuming (i) randoin assortment, two-by-two, of the four daughter kinetochores, (ii) random assortment, two-by-two, of the four chromatids (excluding the kinetochore), and independent occurrence of (i) from (ii). These interpretations are supported by findings in an abnormal meiotic type due to the effects of high temperature, the precocious-b type (cf. No. 4 of this series) and are applicable to configurations of trivalents of autotriploid Paris.
The bearing of the present findings upon chromosome pairing is discussed.
