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



are the appearance of granules in the nuclear wall and an 

 irregularity in its outline (fig. 6). Various stages in the 

 transformation of the nuclear wall have been observed (figs, 



7, 8, 9 and 10). As the figures show, this change con- 

 tinues until finally no definite nuclear membrane remains; 

 in its stead, there is a zone of deeply staining meshes, the 

 fibers of which contain many granules (fig. 11). This 

 meshwork connects the linin reticulum with the cytoplasmic 

 reticulum, forming one continuous network from cell-wall 

 to cell-wall. 



In the younger cells there are but few linin threads and 

 these are delicate and stain but slightly. Later, however, 

 they become coarse, exhibit thickenings and increase so 

 that a linin reticulum entirely fills the nuclear space (figs. 



8, 9, 10 and 11). 



The granular constituent of the cytoplasm, which was at 

 first uniformly distributed, soon becomes more or less 

 massed in irregular patches midway between the nuclear 

 wall and the cell-wall (fig. 4), leaving areas comparatively 

 free from granular matter near the cell-wall and near the 

 nuclear wall. This massing of the granular matter con- 

 tinues until a complete dense zone, the granular zone, is 

 formed at the time when linin, nuclear wall, and cytoplas- 

 mic reticulum form an unbroken network from cell-wall to 

 cell-wall (figs. 11 and 12). The granular zone is constant 

 from this time on until the anaphase, and is occasionally 

 seen even after the daughter-nuclei are formed. Such a 

 zone has been figured by several observers. Juel (1897) 

 shows it as a definite zone in multipolar and bipolar stages; 

 Belajeff (1894) and Osterhout (1897) in the bipolar stage; 

 and Mottier (1897, a and 3) traces of it in prophase, in 

 multipolar and bipolar stages. What the formation of the 

 granular zone has to do with the origin of the spindle is 

 uncertain. It appears to be simply an accumulation of the 

 granular part of the cytoplasm in a definite area. 



Soon after the formation of the continuous reticulum fill- 

 ing the cell, the fibers in the vicinity of the old nuclear 

 wall cease to stain more deeply than the other parts of 



