1. At diakinesis or metaphase in the first division of meioses, 29 divalents appeared.

2. 5 Pollen mother cells undergo meioses through simultaneous cytokinesis and give rise to tetrads of microspores, which are tetrahedrally arranged.

3. 3 Pollen mother cells undergo meioses through simultaneous cytokinesis and give rise to tetrads of microspores, which are mostly terahedrally arranged.

4. We present an analysis of crossover interference in the mouse genome, on the basis of high-density genotype data from two reciprocal interspecific Backcrosses, comprising 188 meioses