EAND : NERVOUS SYSTEM OF LUMBRICID^. 127 



spiudle. These are quite likely " mantle fibres " attached to the chro- 

 mosomes. They exhibited a finely granular structure. 



The anaphase must be a period of very short duration, for figures in 

 which the chromosomes were just separating, or had traversed less than 

 half the distance toward the poles, were rarely found. The few that 

 were found exhibited no unusual features. 



Figure 25 represents a cell in which the chromosomes have nearly 

 completed their migration toward the poles. At the right pole the 

 chromosomes are aggregated into a nearly solid mass. At the left pole 

 they are still somewhat scattered. The sharp cell outline is still pre- 

 served, indicating the presence of the cell membrane. There is a very 

 slight equatorial constriction of the cell. The body of the cell, out- 

 side the spindle figure, is perfectly clear except for a slight trace of in- 

 definite material on one side of the spindle. The interzonal filaments 

 occupy a barrel-shaped region. This shape of the figure is characteristic 

 for this phase, and cells in this condition were very abundant. The bar- 

 rel-shaped figure lies sharply outlined in the surrounding clear space. 

 The interzonal filaments are of granular appearance, and some irregular 

 dark masses occur upon them. 



The presence of a centrosome at the left pole of the figure is doubt- 

 ful. The black granule which appears to occupy the position of the 

 centrosome is much larger than the centrosome usually is at this stage. 

 It is possibly an aberrant chromosome. The axis of the figure is oblique 

 to the plane of the section, the left end being higher. This position 

 favors the obscuring of a centrosome. Although the chromosomes at 

 the right pole are in a nearly compact mass, something of the form of 

 individual chromosomes is still to be distinguished. The centrosome is 

 unmistakable, lying at the apex of the old spindle. The chromatic mass 

 is more smoothly outlined on the polar side, being concave toward the 

 centrosome. This condition is characteristic and is seen to better ad- 

 vantage in the cell represented in the next figure. 



Figure 26 is a somewhat later stage than Figure 25, as is shown by the 

 complete consolidation of the chromosomes and the deeper equatorial 

 constriction of the cell. The cell membrane is still distinctly present, 

 although at some regions it appears fainter and less clearly defined. 

 The cell body, outside the region of the spindle, is still nearly clear. 

 The figure itself is barrel-shaped, as before, but the interzonal filaments _ 

 are more sharply bent at the equator. Each group of daughter chro- 

 mosomes appears to have fused to a solid mass. In the mass at the 

 right pole the position of a lagging chromosome is indicated by a chro- 

 matic process extending toward the equator. 



