Blackman. — Spermatogenesis of Scolopendra. 



PLATE 4. 



All figures magnified 1747 diameters. 

 Fig. 47. Centrosome and portion of nucleus of first spermatocyte during mid 

 prophase. No centrosphere is present. The developing astral ravs 

 abut directly upon the centrosome. 

 Fig. 48. Later prophase. Nuclear membrane disintegrating. The centrosome is 

 now surrounded by a centrosphere, through which some of the astral 

 fibres penetrate, while the majority can be traced only to its surface 

 Fig. 49. Very late prophase. The nuclear membrane has disappeared and the 

 limn network is being drawn toward the centrosome to form the 

 mautle fibres. Centrosome and centrosphere are very distinct and 

 outside the latter another irregular darker area is formed by the 

 closely apposed bases of the astral rays. 

 Figs. 50a, 506. Pole view and side view, respectively, of the centrosome and 

 aster in the metaphase. The centrosomes are nearly divided, but 

 are still connected by a band of similar material. 

 Fig. 51. Centrosome and aster in the anaphase. The centrosomes are fully 

 divided and quite separate from each other. The centrosphere is also 

 nearly entirely constricted. 

 Fig. 52. Centrosome and astral rays during the separation of the centrosome in 

 the prophase of the second spermatocyte division. No centrosphere 

 is present. 

 Fig. 53. Astral system in the metaphase of the second spermatocyte. The cen- 

 trosphere is again very evident. 

 Fig. 54. Portion of one of the small spermatocytes during the metaphase (from 

 the same cell as Fig. 65). The centrosome is elongated in the direc- 

 tion of the axis of the spindle into a cone-shaped body. The centro- 

 sphere is of the same general shape. The astral rays in the polar 

 region are fewer and fainter than those proceeding toward the equa- 

 tor of the cell. The latter are much branched. 

 Fig. 55. One of the small spermatocytes in the early telophase. No centrosphere 

 is present, since the substance forming this in earlier stages has been 

 used up in the lengthening of the equatorial astral rays. 



