Blackman. — Spe: ruatogenesis of Scolopendra. 



PLATE 3. 



All figures magnified 960 diameters. 



Fig. 33. Later metaphase. The spindle has begun its revolution. The centro- 

 somes have completely divided, and the centrosphere is partially 

 constricted. 



Fig. 84. Later stage in the revolution of the spindle. Nearly all of the cytoplasm 

 now appears transparent. 



Fig. 35. Early anaphase. The revolution of the spindle is completed and the 

 chromosomes are being separated. The astral radiations now extend 

 to all portions of the cell. 



Fig. 36. Late anaphase. The chromosomes have nearly reached the poles. In 

 one group there are seventeen chromosomes, while in the other there 

 are only sixteen. 



Fig. 37. Slightly later anaphase, showing the beginning of the constriction of the 

 cell wall. 



Fig. 38. Early telophase of the first spermatocyte. The constriction of the cell 

 is nearly completed. The "Zwischenkorperchen" is very well de- 

 veloped. The chromosomes lie in an irregular clear vesicle. 



Fig. 39. Late telophase. The constriction of the cell is complete, and a portion of 

 the "Zwischenkorperchen" lies in neither cell. The nuclear mem- 

 brane is re-formed, and the chromosomes, with the exception of the 

 accessory chromosome, have become granular. 



Fig. 40. Four drawings showing the shape and size of the chromosomes and the 

 relation they bear to the spindle fibres. In each drawing there is one 

 chromosome which shows a notching at the ends, and is connected 

 with only one pole by mantle fibres. This is the accessory chromo- 

 some, chr'so. ace. 

 Figures 41-46 represent consecutive stages of secondary spermatocytes. 



Fig. 41. Two cells derived from one primary spermatocyte, each in the early pro- 

 phase of the second division. The ordinary chromosomes all show a 

 dumbbell form, while in one cell (the lower) the accessory chromosome 

 is recognizable by its notched ends. The centrosomes are moving apart 

 along the cell membrane. The cells have so rotated that the remnants 

 of the spindle have been detached. 



Fig. 42. Later prophase of the second spermatocyte. Each of the centrosomes is 

 now surrounded by a centrosphere. 



Fig. 43- Metaphase of the second spermatocyte. The accessory chromosome is 

 distinguishable from the others by its size and shape. 



Fig. 44. Anaphase of the second spermatocyte. 



Fig. 45. Early telophase. The chromatin is enclosed in a clear vesicle. The 

 cell wall is being constricted. 



Fig. 46. Early spermatid. 



