Blackman. — Spermatogenesis of Scolopeudra. 



PLATE 6. 



All figures magnified 960 diameters. 



Fig. 77. Early telophase of the second spermatocyte. The nuclei are beginning 

 to be reconstructed. The centrosome is in close contact with the cell 

 membrane. The cell membrane is entirely constricted except for the 

 central portion of the remnants of the spindle, which is drawn out 

 into a narrow connecting cord. 

 Fig. 78. Later telophase. The nuclear membrane has appeared. Centrosome 

 still at periphery. The cells have drawn apart still further, causing 

 still more of the remnants of the spindle to enter into the cord-like 

 bridge between the two cells. 

 Figures 79-101 represent the spermatid and the early stages of its metamorphosis 

 into the spermatozoon. 

 Fig. 79. Early spermatid. The remnants of the spindle have been detached. 



Centrosome still in contact with cell membrane. 

 Fig. 80. Early spermatid, at the time when the nucleus increases rapidly in size 

 by the taking in of material from the cytoplasm, showing rupture of 

 the nuclear membrane. 

 Figs. 81, 82. Both cells are of the same stage. A portion of the nuclear material 

 has the form of hernia-like protrusions, extruded as result of the 

 rapid taking in of material from the cytoplasm. 

 Fig. 83. Stage of about the same age as Figures 81, 82. The extruded portion 



has become entirely separate from the nucleus. 

 Fig. 84. Later stage, immediately following the enlargement of the nuclear vesicle. 

 There is no distinct nuclear membrane. The centrosome having left 

 the cell membrane is migrating toward the nucleus. It shows an 

 elongation in the direction of its movement. A distinct mass of archo- 

 plasm surrounds the centrosome, and small irregular masses are to 

 be seen at various places in the cytoplasm. The chromatin is aggre- 

 gated upon the side of the nucleus nearest the centrosome. 

 Fig. 85. The centrosome has migrated still further, and at its distal end the 

 beginning of the axial filament is seen. The entire structure is en- 

 closed in a mass of archoplasm. 

 Figs. 86-90. Slightly later stages in the formation of the axial filament, showing 

 the appearance of the early axial filament and the relations existing 

 between it and the archoplasm, cytoplasm, and centrosomes. 

 Fig. 91. Later stage in the formation of the axial filament. The archoplasm is 

 gathered about the base of the filament, but has already begun to 

 break up into smaller masses. The chromatin is becoming more 

 evenly distributed. 

 Figs. 92, 93. Stages showing the beginning of the elongation of the cell. The 

 cell membrane on the side opposite the nucleus— the future posterior 

 end of the cell — shows an irregular wavy contour. Portions of archo- 

 plasm have broken off from the main mass around the base of the axial 

 filament, and some of these have migrated to the side of the nucleus 

 opposite the filament, while others are moving along the course of the 

 axial filament. 



