66 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



wall, covering the elongated meshes of the cytoplasmic 

 reticulum (fig. 4). It increases rapidly in quantity about 

 the nucleus without decreasing throughout the rest of the 

 cytoplasm. It is always densest close to the nucleus and 

 from there shades gradually out into the cloudy mass of the 

 cytoplasm. 



As this granular substance begins to accumulate, the 

 meshes of the cytoplasmic reticulum, with the exception of 

 a narrow zone surrounding the nucleus, become radially 

 elongated (figs, 4 and 5). This arrangement, however, 

 does not seem to have any particular significance and soon 

 disappears. In a very short time a zone of granular matter 

 has collected about the nucleus, occupying from one-half 

 to one-third of the space outside of it. It becomes so 

 dense that it entirely obscures the reticulum within it, 

 except that a few fibers may sometimes be visible close to 

 the nuclear wall (iigs. 5 and 6). By this time, the elon- 

 gated meshes of the cytoplasm immediately surrounding 

 the nucleus have been transformed into free fibers, which 

 lie between the granular zone and the nuclear wall. Occa- 

 sionally there is a felt of fibers bounding the outer edge of 

 the granular zone, and, by reason of their deep blue color, 

 standing out conspicuously against the yellowish brown 

 granular matter (figs. 6 and 8). This is by no means 

 constant. 



By the time the granular zone is completely formed, the 

 radial arrangement of the reticulum outside of it has entirely 

 disappeared (fig. 6). The granular zone is composed of a 

 dense mass of granules, most of which are larger than those 

 that gave the cytoplasm its cloudy appearance in the earli- 

 est stage. In this form it remains unchanged until the end 

 of the anaphase. 



While the granular zone has been gathering, the linin in 

 the nucleus has increased somewhat in quantity and in 

 staining power. About this time, the cytoplasm loses its 

 regular structure, as shown in figs. 6, 7, etc. Soon the 

 fibers immediately outside of the nuclear wall come into 

 clearer view, as though the granular matter had withdrawn 



