The Journal of experimental zoology . ve position (Fig. i, b). The period at which these bodies 514 Edmund B. Wilson. Figure i. Alydus pilosulus.—a, Contraction-phase of synaptic period, accessory (Jt) in the form of a con-densed chromosome-nucleolus attached to a large plasmosome (p); h, spermatocyte-nucleus, middlegrowth-period, showing large diffused chromosomes—accessory still attached to the plasmosome—and the two condensed w-chromosomes on opposite sides of the nucleus; c, early prophase of firstdivision, showing all of the chromosomes, the larger ones condensing; d, late prophase, showi
The Journal of experimental zoology . ve position (Fig. i, b). The period at which these bodies 514 Edmund B. Wilson. Figure i. Alydus pilosulus.—a, Contraction-phase of synaptic period, accessory (Jt) in the form of a con-densed chromosome-nucleolus attached to a large plasmosome (p); h, spermatocyte-nucleus, middlegrowth-period, showing large diffused chromosomes—accessory still attached to the plasmosome—and the two condensed w-chromosomes on opposite sides of the nucleus; c, early prophase of firstdivision, showing all of the chromosomes, the larger ones condensing; d, late prophase, showingaccessory (Jt) and the two m-chromosomes still separate; e, slightly later prophase, showing allof the chromosomes; /, initial anaphase, first division, the ra-chromosomes separating; ^, polar view ofmetaphase-group, first division; h, polar view of metaphase-figure, second division; /, j, initialanaphases, second division; k, spermatogonial metaphase-group; /, m, n, 0, anaphases of seconddivision. Studies on Chromosomes. 515. Figure i.^ The figures are all drawn to the same scale as those of the preceding study. 5i6 Edmund B. Wilson. condense into the compact form appears to vary considerably,for they cannot always be distinguished until the later growth-period, and it should be noted that during the pale period thenuclei often show a variable number of smaller deeply-staininggranules. I believe, however, that there can be no doubt as tothe nature of the two larger bodies on account of their great con-stancy, their size, and the completeness of the series that connectsthe earlier with the later conditions (such as is shown in Fig. i, c),where no doubt of their nature can exist. The persistence of thelarger chromosome-nucleolus (accessory) throughout all thesestages without any considerable change renders it manifestlyimpossible that it should give rise to the m-chromosome bivalent,either directly as assumed by Paulmier and Montgomery, or bydivision into two univalents
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