Blackjian. — Spermatogenesis of Scolopendra. 



PLATE 9. 



Figures 153, 160, are magnified 520 diameters ; Figures 164, 165, 168, 170-173, are mag- 

 nified 656 diameters; all others, 800 diameters. 



Fig. 148. Polar view of centrosome, centrospliere, and aster of spermatocyte of the 

 large type in the anaphase. 



Fig. 149. Polar view of spermatocytes of the small type in the anaphase. 



Figs. 150, 151. Late prophase of second spermatocyte. In each case the centro- 

 somes are in contact with the cell membrane, but the plane of the sec- 

 tion is tangential to the membrane at this point. 



Fig. 152. Metaphase of second spermatocyte. 



Fig. 153. Anaphase of second spermatocyte. 



Fig. 154. Prophase of the first spermatocyte of the small type. Chromosomes 

 are becoming dense. Centrosomes (at left of nucleus) are migrating 

 toward nuclear membrane. 



Fig. 155. Later prophase. The centrosomes are moving apart along the nuclear 

 membrane. 



Fig. 156. Late prophase. Nuclear membrane is breaking down and spindle is 

 being formed. (Compare Figs. 62, 63.) Only one centrosome is in 

 focus. 



Fig. 157. Short spindle of early metaphase. (Compare Fig. 64.) 



Fig. 158. Later metaphase. The spindle has lengthened. 



Figs. 159, 160. The modified spindle. (Compare Fig. 66.) 



Fig. 161. Late anaphase of division of first spermatocyte of small type. 



Fig. 162. Telophase of first mitosis, small-type spermatocyte. 



Fig. 163. Metaphase of second mitosis of small-type spermatocyte. 



Figs. 164, 165. Metaphase of second division of spermatocyte of large type, to show 

 different appearance of accessory and ordinary chromosomes. 



Fig. 166. Early stage of spermatid. 



Fig. 167. Later stage. (Compare Figs. 95, 96.) 



Fig. 168. Late spermatid (compare Fig. 103), showing one of the lateral centro- 

 somes. The other one is out of focus. 



Fig. 169. Young spermatozoa (compare Fig. 106), showing head, acrosome, and 

 axial filament. 



Fig. 170. Spermatozoa of same stage as Figure 109. In those at the left the pres- 

 ence of the centrosome is shown by the darker mass at the base of the 

 head. 



Fig. 171. Later stage, showing head and portion of acrosome (compare Fig. 111). 

 In the third one from the top the extra-nuclear centrosome appears. 



Fig. 172. Portion of follicle in cross section, showing the appearance of the mature 

 or nearly mature spermatozoa. The cytoplasmic sheath, even in the 

 head region, is quite pronounced. 

 Portions of mature spermatozoa. In the one at the left the intra-nuclear 

 centrosomes are seen (similar to Fig. 120). 



