Davis. — Spermatogenesis. 



PLATE 3. 



Fig. 37. Stage d, primary spermatocyte of Arphia tenebrosa. Two mono- 

 somes are present. 



Figs. 38-40. Nuclei of primary spermatocytes of Hippiscus tuberculatus 

 showing successive stages in the splitting of the spireme tlireads. 



Figs. 41-44. Chortophaga irlridifasciata. 



Figs. 41, 42. Stage h, primary spermatocytes. The plane of Fig. 42 is 

 perpendicular to that of Fig. 41. 



Figs. 43, 44. Nuclei slightly older than those of Figs 41, 42, showing de- 

 velopment of spireme threads from chromatic masses. 



Fig. 45. Stage h, primary spermatocyte of Melanophis femoratum. 



Fig. 46. Stage /, primary spermatocyte of Dissosteira Carolina. The mono- 

 some is seen below at the right. 



Figs. 47-52. Stenobothrus curtipennis. 



Fig. 47. Stage a, primary spermatocyte. The monosome is inclosed in a 



separate vesicle. 

 Fig. 48. Stage e, primary spermatocyte. 

 Figs. 49-50. Stage e, nuclei of primary spermatocyte. In Figure 49 the 



monosome lies below and at some distance from the distal pole, 



while in Figure 50 it lies close to the pole. 

 Fig. 51. Stage e, cross section of polar loops and monosome near the distal 



pole. 

 Fig. 52. Stage /, primary spermatocyte. The bipartite structure of the 



monosome is well shown. 



Figs. 53-56. Steiroxys trilineata. 



Fig. 53. Stage a, primary spermatocyte. Owing to imperfect fixation the 

 chromatin is shrunken away from the nuclear wall. The mono- 

 some lies outside the nucleus. 



Fig. 54. Same stage as Figure 53, but the fixation of the cell is good. 



Fig. 55. Stage c, primary spermatocyte. The monosome has become ap- 

 plied to the nuclear membrane. 



Fig. 56. Stage d, primary spermatocyte. The monosome now lies within 

 the nucleus. The mitochondrion body is seen in the cytoplasm 

 above the nucleus 



