The gemini in Zea Mays vary in number from 9 to 12. Even in one and the same race there are certain variations. The sugar corns have generally a larger number and the starch corns smaller; and there seem to exist certain connections between those two kinds of numbers of gemini, and it is likely that the smaller numbers were reduced from 12 and consequently the number 12 is original for all the races of Zea Mays. The size and shape of gemini are tolerably different as shown in the side view of the metaphase, and there are two sets of them, that is, each sort of gemini is duplicated. In the equatorial plate of the homotype division some pairs of chromosomes come in contact with each other or even fuse up altogether. Those two facts, chiefly the former, lead to the view that Zea Mays is probably a tetraploidal plant, not necessarily apogamic. It is suggested that the production of innumerable races of Zea Mays has a certain relation with the duplication of chromosomes, resulting in the double number derived from an original form which had probably 6 chromosomes in reduced number. An abnormal case was found in a race 'Amber rice pop corn.' The geminial chromosomes, though not all, separate from each other without intervention of the traction fibres, and the individual separated member divides again transversely. The homotype division is mostly skipped and the resting nuclei are directly formed. Sometimes few chromosomes are left in cytoplasm and dwarf nuclei are formed.