BLACKMAN : THE SPERMATOGENESIS OF SOOLOPENDRA. 35 



toward opposite ends of the cell. This results in a distortion of the 

 spindle, as shown in Figures 33-35, 147. This distortion is really the 

 expression of a rotation of the mitotic figure, such as often occurs in the 

 maturation mitosis of eggs. In tins rotation the centrosomes always lead, 

 and very plainly seem to exert an attractive force upon the remainder of 

 the spindle. In Figure 145 is shown a nietaphase in which the formation 

 of the spindle has just been completed and the rotation has not yet begun. 

 Figure 33 shows the spindle at the time these distortions first begin, and 

 the same is shown in the fragment of the spindle in Figure 147. Figures 

 34, 35, represent later stages, in which the revolution is nearly accom- 

 plished. As will be seen from the accompanying drawings, this change 

 in the position of the mitotic figure occurs during the metaphase — i. e. 

 before the chromosomes have been divided and have begun to move toward 

 the poles. However, as soon as the spindle is oriented lengthwise of 

 the cell the separation of the chromosomes begins and the cell passes 

 into the anaphase (Fig. 35). 



The rotation of the spindle in this manner accomplishes two things 

 which are beneficial to the cell. First, the plane of division is so altered 

 that the ensuing cleavage of the cytosome may be accomplished with the 

 least possible expenditure of energy, and by this rotation the centrosomes 

 are brought into closer relation with all parts of the cytoplasm. This 

 apparently aids in the reconstruction of the latent archoplasm, laid down 

 in the hyaloplasmic areas, into its kinetic form, the fibrillar astral rays. 

 By the time the revolution of the spindle is accomplished practically all 

 the archoplasm has been converted into the fibrillar form and the cell 

 is ready for division. It is now very evident that the cytoplasm has a 

 reticular structure, as, indeed, it has had at all times, although during the. 

 earlier stages this structure was not easily distinguished owing to the 

 extraordinary opacity of the inter-reticular substance. 



When the revolution of the spindle and the reconstruction of the archo- 

 plasm has been accomplished, the cell proceeds to divide. The spindle 

 lengthens, and by this elongation the chromosomes are divided and drawn 

 apart into two groups (Fig. 3G). The centrosomes move toward the 

 cell membrane (Fig. 3G), and finally with the enveloping centrosphens 

 come to rest near its inner surface (Fig. 37). In the early telophase the 

 chromosomes become aggregated into two masses at opposite ends of 

 the cell at a short distance from the centrosomes. They are so closely 

 crowded together that their individuality is apparently lost, and the mass 

 thus formed is contained in a clear vacuole of hyaloplasm (Fig. 38). In 

 the later stages of the telophase the chromosomes separate and become dis- 



