Chapter VII: Bibliography

=1=. Atkinson, Geo. F., 1899. Studies on Reduction in Plants, Bot. Gaz., vol. 28.

=2=. Baumgartner, W. J., 1902. The Spermatid Transformations of _Gryllus assimilis_, etc., Kans. Univ. Sci. Bull., vol. 1, No. 1.

=3=. Brauer, A., 1893. Zur Kenntniss der Spermatogenese von _Ascaris megalocephala_, Arch. mikr. Anat., vol 42.

=4=. Carnoy, 1895. La Cytodiérese chez les Arthropodes, La Cellule, vol. 1.

=5=. Cholodkovsky, N., 1894. Zur Frage über die Anfangsstadien der Spermatogenese bei den Insecten, Zool. Anz., vol. 17.

=6=. Griffin, B. B., 1899. Studies on Maturation, Fertilization and Cleavage of _Thalassema_ and _Zirphæa_, Jr. Morph., vol. 15.

=7=. Häcker, Valetin, 1897. Ueber weitere Uebereinstimmungen zwischen den Fortpflianzungsvorgängen der Tiere und Pflanzen, Biol. Cent., vol. 17.

=8=. Henking, H., 1890. Untersuchungen über die ersten Entwicklungsvorgänge in den Eiern der Insecten. 2. Ueber Spermatogenese und deren Beziehung zur Eientwicklung bei _Pyrrhocoris apterus_ M., Z. wiss. Zool., vol. 51.

=9=. Henking, H., 1892, idem. 3. Specielles und Allgemeines, _ibid._, vol. 54.

=10=. Ischikawa, 1891. Studies of Reproductive Elements. Spermatogenesis, Ovogenesis and Fertilization in _Diaptomus_ sp., J. Coll. Sc. Imp. Univ. Japan, vol. 5.

=11=. Kingsbury, B. F., 1902. The Spermatogenesis of _Desmognathus fusca_, Am. Jour. Anat., vol. 1, No. 2.

=12=. Montgomery, T. H., jr., 1898. The Spermatogenesis in _Pentatoma_ up to the Formation of the Spermatid, Zool. Jahrb., vol. 12.

=13=. Montgomery, T. H., jr., 1898. Chromatin Reduction in the Hemiptera: a Correction, Zool. Anz., vol. 22.

=13=_a_. Montgomery, T. H., jr., 1898. Observations on Various Nucleolar Structures of the Cell, Biol. Lect. of the Woods Holl Laboratory, 1898.

=14=. Montgomery, T. H., jr., 1900. The Spermatogenesis of _Peripatus balfouri_ up to the Formation of the Spermatid, Zool. Jahrb., vol. 14.

=15=. Montgomery, T. H., jr., 1901. A Study of the Germ Cells of Metazoa, Trans. Amer. Phil. Soc., vol. 20.

=16=. McClung, C. E., 1899. A Peculiar Nuclear Element in the Male Reproductive Cells of Insects, Zool. Bull., vol. 2.

=17=. McClung, C. E., 1900. The Spermatocyte Divisions of the Acrididæ, Kans. Univ. Quart., vol. 9, No. 1.

=18=. McClung, C. E., 1901. Notes on the Accessory Chromosome, Anat. Anz., Bd. 20, Nos. 8, 9.

=19=. McClung, C. E., 1902. The Accessory Chromosome—Sex Determinant? Biol. Bull., vol. 3, Nos. 1, 2.

=20=. Moore, J. E. S., 1895. On the Structural Changes in the Reproductive Cells during the Spermatogenesis of Elasmobranchs, Quart. J. Micr. Sc., vol. 38.

=21=. Paulmier, F. C., 1898. Chromatin Reduction in the Hemiptera, Anat. Anz., vol. 14.

=22=. Paulmier, F. C., 1899. The Spermatogenesis of _Anasa tristis_, Jr. Morph., vol. 15.

=23=. Platner, G., 1886. Die Karyokinese bei den Lepidopteran als Grundlage für eine Theorie der Zelltheilung, Internat. Monatsschr. Anat. Histol., vol. 3.

=24=. Rath, O. vom, 1891. Ueber die Reduction der Chromatischen Elemente in der Samenbildung von _Gryllotalpa_, Ber. Naturf. Ges. Freiburg, vol. 6.

=25=. Rath, O. vom, 1892. Zur Kenntniss der Spermatogenese von _Gryllotalpa vulgaris_ Latr., Arch. Mikr. Anat., vol. 40.

=26=. Rath, O. vom, 1895. Neue Beiträge zur Frage der Chromatinreduction in der Samen und Eireife, _ibid._, vol. 4.

=27=. Sabatier, A., 1890. De la Spermatogénese chez les Locustides, Comptes Rend., vol. 111.

=28=. Sutton, W. S., 1900. The Spermatogonial Divisions of _Brachystola magna_, Kans. Univ. Quart., vol. 9, No. 2.

=29=. Toyama, K., 1894. On the Spermatogenesis of the Silkworm, Bull. Coll. Agric. Imp. Univ. Japan, vol. 2.

=30=. V. la Valette St. George, 1897. Zur Samen-und Eibildung beim Seidenspinner (_Bombyx mori_), Arch. mikr. Anat., vol. 50.

=31=. Wagner, J., 1896. Beiträge zur Kenntniss der Spermatogenese bei den Spinnen, Arb. Nat. Ges. St. Petersburg, vol. 26.

=32=. Wilcox, E. V., 1895. Spermatogenesis of _Caloptenus femur-rubrum_ and _Cicada tibicen_, Bull. Mus. Comp. Zool. Harvard Univ., vol. 27.

=33=. Wilcox, E. V., 1896. Further Studies on the Spermatogenesis of _Caloptenus femur-rubrum_, _ibid._, vol. 29.

=34=. Wilcox, E. V., 1897. Chromatic Tetrads, Anat. Anz., vol. 14.

=35=. Wilcox, E. V., 1901. Longitudinal and Transverse Divisions of Chromosomes, Anat. Anz., Bd. 19, No. 13.

=36=. Wilson, E. B., 1900. The Cell in Development and Inheritance. New York; 2d ed.

=37=. de Sinéty, R., 1901. Recherches sur la Biologie et l’Anatomie des Phasmes, La Cellule, Tome 19, 1er fascicule.

DESCRIPTION OF FIGURES.

Drawings were made with a _camera lucida_, the optical combination being a 1–16 B. & L. objective and a Watson “Holoscopic” ocular No. 7. Details were studied with a Zeiss 2-mm. apochromat, N. A. 1.30. As reduced in reproduction, an enlargement of 1500 diameters exists. Photomicrographs, excepting those of figures 37 and 38, were made by the use of the arc light and horizontal camera. The exceptions represent illumination by ordinary diffuse daylight. In all cases the lenses used were the Zeiss 2 mm., N. A. 1.30 objective and projection oculars. A Watson “Parachromatic” oil-immersion condenser of 1.30 N. A. was employed to illuminate the objects. In use it was stopped down to between .75 N. A. and 1.0 N. A.

Explanation of Plate VII.

FIG. 1. Pole view of spermatogonial metaphase, showing the thirty-three chromosomes. It will be observed that the chromosomes are of unequal sizes, and that the large ones arrange themselves in a circle on the outside of the figure.

FIG. 2. Very young spermatocyte. The chromatin derived from the breaking down of the spermatogonial chromosomes in a diffuse condition, with no trace of a linear arrangement. The accessory chromosome _x_ on the periphery of the nucleus, darkly staining and homogeneous.

FIG. 3. Early stage in the formation of the spireme. In the cytoplasm the remains of the spermatogonial spindle. The cell has entered upon the growth period.

FIG. 4. A later stage in the spireme formation. The accessory chromosome larger and more flattened. A surface view shows it as an apparently fenestrated plate. The remains of the two spermatogonial spindles still persisting.

FIG. 5. First appearance of definite chromosomes. One shown entire with longitudinal and cross-divisions marked. The accessory chromosome is here seen to be in a spireme condition.

FIG. 6. Condition of the chromosomes after further contraction of the early segments. As here shown, they are more granular than is usually the case.

FIG. 7. Common types of the prophase chromosomes.

FIG. 8. A cell in which one of the chromosomes has its halves widely separated along the longitudinal division, forming Paulmier’s double-V figure.

FIG. 9. In this cell may be seen the variation in form and size of the early spermatocyte chromosomes.

FIG. 10. Two cells of the late prophase, with the chromosomes at almost the extreme degree of concentration.

FIG. 11. Chromosomes of cells in the stage shown in figure 10. These represent the different types of rings, crosses, etc., commonly observed in first spermatocytes just before the formation of the mitotic figure.

FIG. 12. Different forms assumed by the accessory chromosome in the prophase of the first spermatocytes of _Xiphidium_.

FIG. 13. Metaphase of the first spermatocyte. The accessory chromosome is seen at one pole of the spindle, to which it has moved before the separation of the chromatids of the remaining chromosomes.

FIG. 14. Another cell in about the same stage as that represented in the preceding figure.

FIG. 15. A first spermatocyte metaphase in which the accessory chromosome has not as yet moved to the pole of the spindle. This is uncommon in _Orchesticus_, but frequent in _Anabrus_.

FIG. 16. Pole view of a first spermatocyte metaphase, showing seventeen chromosomes. The variation in size of the elements, so marked in the spermatogonia, is even more pronounced here. This is a cell similar to that of figure 15, in which the accessory chromosome lies in the equatorial plate.

Explanation of Plate VIII.

FIG. 17. Two cells in metaphase—a pole view of one and an oblique view of the other. The accessory chromosome does not show in the former, the cell being such a one as is represented in figures 14 and 15.

FIG. 18. Pole view of another cell, showing but sixteen chromosomes.

FIG. 19. Early anaphase of the first spermatocyte, with the accessory chromosome already at one pole.

FIG. 20. Mid-anaphase, with the giant chromosome still undivided.

FIG. 21. Later anaphase, in which the accessory chromosome is seen at the lower pole. This figure shows, also, the character and extent of the intercellular material.

FIG. 22. Later anaphase. The accessory chromosome at the upper pole. An undivided chromosome lying between the groups of daughter chromosomes.

FIG. 23. About the stage of figure 22, but the lagging chromosome has divided.

FIG. 24. Very late anaphase. Here, again, the lagging chromosome is divided.

FIG. 25. Pole view of first spermatocyte telophase, showing the accessory chromosome at one side of the daughter chromosomes.

FIG. 26. Pole view of a cell in the same stage as that represented in figure 25. Here, however, the accessory chromosome is not present.

FIG. 27. Lateral view of telophase, with the accessory chromosome in the lower daughter-cell.

FIG. 28. Fragment of second spermatocyte, showing the chromosomes in metaphase. The relative sizes of the accessory chromosome and the remaining chromosomes is well shown.

FIG. 29. Metaphase of a second spermatocyte, in which the accessory chromosome is not present.

FIG. 30. Anaphase of second spermatocyte, in which there is no accessory chromosome.

FIG. 31. Anaphase of second spermatocyte, where the accessory chromosome is present—_x_^1 and _x_^2.

FIG. 32. Telophase of the same class of second spermatocytes. The accessory chromosome extends out from the mass of chromosomes at each pole—_x_^1 and _x_^2.

FIG. 33. Telophase of the class of second spermatocytes from which the accessory chromosome is absent.

Explanation of Plate IX.

FIG. 34. Photomicrograph of early spireme stage of first spermatocyte, showing peripheral position of the accessory chromosome _x_. At the left, secondary spermatogonia, last generation. × 1300.

FIG. 35. A late prophase, showing accessory chromosome _x_, and spindle remains _s_ (_cf._ figs. 3 and 4). × 1300.

FIG. 36. Coarse spireme of first spermatocyte. × 1300.

FIG. 37. Prophase, with chromosomes in the form of long segments. At _a_, the cell drawn in figure 9. In the cyst at the left are spermatocytes in a later stage, with the chromosomes homogeneous. × 1000.

FIG. 38. Prophase with segments divided longitudinally and across. At _a_ is one shown _en face_. Accessory chromosome at x. × 1000.

FIG. 39. Metaphase and anaphase of first spermatocyte. The accessory chromosome _x_ at one pole of the spindle. Lagging chromosome at _c_. × 1300.

Explanation of Plate X.

FIG. 40. Anaphase of first spermatocyte. Accessory chromosome _x_ at one pole. The form of chromosome in the anaphase well shown. The lagging chromosome _c_ seen in two cells. × 1300.

FIG. 41. Anaphase of the first spermatocyte, showing the longitudinally divided condition of the accessory chromosome _x_ in the cell near the center. Compare with the accessory chromosome in the metaphase of second spermatocyte, figure 43. × 1300.

FIG. 42. Second spermatocyte in metaphase. In most of the cells the focus is upon the ends of the chromosomes, but in one a side view is obtainable. Compare with the chromosome of the upper cell in figure 40. No accessory chromosome in most of the cells in focus. × 1300.

FIG. 43. Second spermatocyte metaphase and spermatids. Note the relative sizes of the accessory chromosome and the other chromosomes. In the spermatids the accessory chromosome has taken its place on the periphery of the nucleus in the same way that it does in the prophase of the first spermatocyte. × 1300.

FIG. 44. Anaphase of the second spermatocyte, showing the accessory chromosome _x_ separated. Other cells in metaphase. × 1300.

FIG. 45. Telophase of the second spermatocyte. Two daughter-cells with persisting spindle between, showing the accessory chromosome _x_ in each. Other nuclei in focus show no accessory chromosomes. × 1300.

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TRANSCRIBER’S NOTES

1. Silently corrected obvious typographical errors and variations in spelling. 2. Retained archaic, non-standard, and uncertain spellings as printed. 3. Enclosed italics font in _underscores_. 4. Enclosed bold font in =equals=. 5. Denoted superscripts by a caret before a single superscript character.