Davis. — Spermatogenesis. 



PLATE 2. 



Figs. 18-20. Steiroxys trilineata. 



Polar view, metaphase of secondary spermatogonia. 



Resting stage of secondary spermatogonia. The monosome lies 



outside the nucleus in a separate vesicle. 

 Metaphase of secondary spermatogonia. 

 Prophase of secondary spermatogonia in Stenobothrus curtipennis. 



Figs. 22-26. Dissosteira Carolina. 



Fig. 22. Cross section of chromosomes during telophase of last spermato- 

 gonial division. The monosome is compact and inclosed in a 

 separate vesicle. 



Fig. 23. Telophase of last spermatogonial division. The monosome shows 

 a distinctly bipartite structure. 



Figs. 24, 25. Late telophase of last spermatogonial division. Owing to 

 imperfect fixation the chromatin is shrunken away from the 

 nuclear wall. The monosome is still inclosed in a separate vesicle. 



Fig. 26. Stage a, primary spermatocyte. The monosome is shown above. 



Fig. 27. Stage a, primary spermatocyte of Arphia tenebrosa. Two mono- 

 somes are present. 



Figs. 28-34. Dissosteira Carolina. 



Fig. 28. Stage b, primary spermatocyte. 



Fig. 29. Stage c, primary spermatocyte. The monosome now lies within 



the nucleus. 

 Fig. 30. Stage c, a little later than Fig. 29. 

 Figs. 31, 32. Stage d, primary spermatocyte. 

 Fig. 33. Stage e, distal pole of nucleus of primary spermatocyte. 

 Fig, 34. Stage e, primary spermatocyte. 

 Fig. 35. Stage e, distal pole of nucleus of Arphia tenebrosa. The monosome 



is seen below in the figure. 

 Fig. 36. Stage e, cross section of polar loops near distal pole. 



