=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_.