similar phenomenon in the male germ cells of Scolopendra, where the spindle remnants of both the first and the second spermatocyte divisions are eliminated during a rotation of one daughter cell upon the other. It seems possible, therefore, that this globule, composed principally of the substance of the interzonal filaments, is not comparable with the spermatocyte of ordinary spermatogenesis, and therefore not with a polar body in ovogenesis. The smaller of the two bodies resulting from the real mitosis which follows the elimination of the interzonal body bears a striking resemblance, it must be admitted, to the polar cell of eggs, and it is unquestionably the result of a true, though modified, cell division. This phenomenon seems, however, never to have been seen in the spermatogenesis of any other animal. There is here an equal division of chromatin accompanied by a very unequal division of the cytoplasm, precisely as in the formation of the polar cell in eggs. The small cell apparently begins to undergo a metamorphosis parallel to that of its larger sister cell, as Meves has maintained. Although Meves believes that the small cell eventually degenerates, positive evidence of this has not yet been produced. If it is to be interpreted as the homologue of a polar cell, the question at once arises, Which of the two polar cells usually produced does it represent? From the standpoint of Meves, the first body might be looked upon as a partially abortive attempt to produce the equivalent of the first polar cell, and the second body might then be regarded as in some sense the equivalent of the second polar cell; but even were his view about the first (interzonal) body correct, the division of nuclear substance accomplished by the formation of the second bud would more strongly point to this, rather than the first, as being the homologue of the first polar cell. That view is, perhaps, strengthened by the facts here presented, which tend to show that the body first produced has nothing whatever to do with cell division, and that in the occasional doubling of the centrosome (Figures 10, 11) some progress is made toward a second cell division, which, if completed, would result in the formation of either two spermatids or a second true polar cell. However, it must be admitted that, on the assumption that the interzonal body has nothing to do with an attempted cell division, the peculiar changes passed through by the chromatin preceding and during the period of the elimination of that body remain unexplained and without a parallel. On the other hand, the beginning metamorphosis of the small nucleated body (second bud) suggests that it is the equivalent of a spermatid rather than a spermatocyte of the first order, and this view is strongly supported by the statement of Meves that in Vespa germanica the cell division corresponding to this results in the production of two spermatids of equal size. BIBLIOGRAPHY. Blackman, M. W. :05. The Spermatogenesis of Myriapoda. III. The Spermatogenesis of Scolopendra heros. Bull. Mus. Comp. Zoöl. Harvard Coll., Vol. 48, No. 1, pp. 1-138, 9 pl., 9 fig. Mark, B. L. '81. Maturation, Fecundation, and Segmentation of Limax campestris, Binney. Bull. Mus. Comp. Zoöl. Harvard Coll., Vol. 6, pp. 173–625, 5 pl. Meves, F. :03. Ueber "Richtungskörperbildung" im Hoden von Hymenopteren. Anat. Anz., Bd. 24, pp. 29-32, 8 Fig. Paulmier, F. C. '99. The Spermatogenesis of Anasa tristis. Jour. Morph., Vol. 15, Suppl., pp. 223-272, 2 pl., 6 fig. Prowazek, S. :01. Spermatologische Studien. Arb. Zool. Inst. Wien, Bd. 13, pp. 197– 236, Taf. 11 u. 12, 2 fig. Zimmermann, K. W. '91. Über den Kernteilungsmodus bei der Spermatogenese von Helix pomatia. Verh. Anat. Gesell., Bd. 5, pp. 187-193. EXPLANATION OF PLATE. All figures were drawn with the aid of a camera lucida and are magnified 2073 diameters. FIGURE 1. Primary spermatocyte, resting stage. FIGURE 2. Primary spermatocyte; the two centrosomes moving apart. FIGURE 3. poles of cell. FIGURE 4. Proximal finger-like process of the cell, terminating in the proximal centrosome; from the distal centrosome extend prominent extranuclear fibres. Nucleus of primary spermatocyte, showing sixteen dyads. Cross section of a primary spermatocyte in the same stage as that of Primary spermatocyte; the centrosomes have arrived at opposite FIGURE 5. FIGURE 6. Figure 9. FIGURE 7. Elongation of the nucleus toward the distal centrosome. FIGURE 8. The nucleus exhibits a spindle-shaped elongation, and intranuclear spindle fibres are established. FIGURE 9. The interzonal body has migrated to the base of the finger-like process. FIGURE 10. The interzonal body in the course of being constricted off from the cell. FIGURE 11. The interzonal body is detached, and there is a typical spindle in the beginning of the metaphase. FIGURE 12. Late anaphase. FIGURE 13. FIGURE 14. FIGURE 15. Finger-like process surmounted by chromatin of polar cell. |