(1) The length of the mitotic spindle, i. e. the distance between the two centrosomes, at the stage of the metaphase when the chromosomes are undergoing constriction in the equatorial plane, appears to be a constant for each spermatogenetic mitosis of the species. The lengths found are 6.9, 10.2 and 7.8 µ for the secondary spermatogonia and primary and secondary spermatocytes respectively.

(2) The length of the mitotic spindle at the conclusion of the metaphase when the daughter-chromosomes are ready to move apart appears to be a constant for each spermatogenetic mitosis of the species. The lengths found are 7.1, 10.4 and 8.1 µ for the secondary spermatogonia and primary and secondary spermatocytes respectively.

(3) The length of the mitotic spindle in the earliest anaphase, i. e. at the moment when the daughter-chromosomes have begun to move apart, appears to be a constant for each spermatogenetic mitosis of the species. The lengths found are 7.3, 10.7 and 8.3 µ for the secondary spermatogonia and primary and secondary spermatocytes respectively.

(4) The ratio between the lengths of the mitotic spindle at the conclusion of the primary and secondary spermatocyte metaphases is almost identical with the ratio between the radii of two spheres of which the volume of one is equal to twice that of the other ; and the volume of the primary spermatocyte cell must be equal to twice that of the secondary spermatocyte at this stage, because no growth or resting stage intervenes.

(5) The ratio between the lengths of the mitotic spindle at the conclusion of the primary spermatocyte and secondary spermatogonial metaphases is almost identical with the ratio between the radii of two spheres of which the volume of one is equal to three times that of the other. The initial volume of the primary spermatocyte cell must be half that of the secondary spermatogonium, because the latter divides to form two daughter primary spermatocytes; but the large size of the last-named, observed at the close of the growth period, does not refute the suggestion that the initial volume is increased six-fold during this period.

(6) If coincidence is not responsible for the apparent connection between the ratios mentioned above, correction is established between the cell volume and length of spindle in the spermatogeiietic metaphases of this species.

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