204 PROCEEDINGS OF THE ACADEMY OF [Feb., 



ScHREiNER, A. and K. E. 1904. Die Reifungsteilungen bei den Wirbeltieren. 



Ein Beitrag zur Frage nach der Chromatinreduktion. Anat. Anz., 24. 

 SiNETT, R. DE. 1901. Recherches sur la Biologie et I'Anatomie des Phasmes. 



La Cellule. 

 Strasburger, E. 1904. Ueber Reduktionsteilung. Sitzh. preuss. Akad. Wiss. 



Berlin. 

 Stricht, O. Van der. 1898. La formation des deux globules polaires et I'appa- 



rition des spermocentres dans I'oeuf de Ttiysanozoon Brocchi. Arch, de 



Biol, 15. 

 Sutton, W. S. 1900. The Spermatogonia! Divisions in Brachystola magna. 



Bull. Univ. Kansas, 9. 

 1902. On the Morphology of the Chromosome Group in Brachystola 



magna. Biol. Bull., 4. 



1903. The Chromosomes in Heredity. Ibid., 4. 



VoiNov, D. N. 1903. La spermatogenese d'ete chez le Cybistes roeselii. Arch. 



zool. exper. gen. (4), 5. 

 Wagner, J. 1896. Einige Beobachtungen iiber die Spermatogenese bei den 



Spinnen (Vorlaufige Mittheilung). Zool. Am., 19. 

 Wallace, L. B. 1900. The Accessory Chromosome in the Spider. Anat. Anz., 



18. 

 Wilcox, E. V. 1895. Spermatogenesis of Caloptenus femur-rubrum and Cicada 



tibicen. Bull. Mus. Com. Zool. Harvard Univ., 27. 

 Winiwarter, H. von. 1900. Recherches sur I'Ovog^nSse et I'Organog^nlse 



de rOvaire des Mammiferes (Lapin et Homme). Arch, de Biol., 17. 



Explanation of Plates IX and X. 



All the figures were drawn by the author with the aid of the camera lucida, at a 

 magnification of about 1800 diameters. In all N. 2 denotes the heterochromosome. 



Plate IX. Syrbula acuticornis Bruner. 

 Fig. 1. — Spermatogonium, rest stage. 

 Figs. 2-6. — Spermatogonia, successive prophases. 

 Figs. 7, 8. — Spermatogonia, pole views of the monaster stage. 

 Fig. 9. — Lateral view of preceding stage. 

 Fig. 10.— Lateral view of spermatogonic anaphase. 

 Fig. 11. — Pole view of first spermatocyte, showing all the chromosomes, 



shortly after preceding stage. 

 Figs. 13-15. — First spermatocytes, successive early stages; in 15 only the 



nucleus shown. 

 Fig. 16. — Rest stage of first spermatocyte. 



Figs. 17, 18. — Successive stages immediately following the preceding. 

 Figs. 19-22. — Successive stages of the synapsis, all lateral views, 19 showing 



only the nucleus. 

 Figs. 23-25. — Nuclei in post-synapsis stage. 

 Fig. 26. — Bivalent heterochromosome of this stage, consisting of two closely 



apposed univalent members, of which the upper one is stippled, 

 Figs. 27-31. — Successive prophases of first maturation mitosis; in the first 



three only the nucleus shown. 

 Figs. 32, 33. — Lateral views of the first maturation spindle; fig. 33 seen 



obliquely so that only one spindle pole shows. 



Plate X, Figs. 34-40. — Syrbula acuticornis (continuation). 



Figs. 34-36. — Successive anaphases of first maturation mitosis; in 36 the 



largest chromosome of the upper plate is longitudinally split, but so 



that one split half covers the other. 

 Fig. 37. — Oblique lateral view of one daughter chromosome plate, anaphase 



of the same mitosis. 

 Fig. 38. — Pole view of chromosome plate of the second spermatocyte. 

 Fig. 39. — Lateral view of second maturation spindle. 



