278 H. M. KINGERY 



they develop into the definitive ova. These cells of the germinal 

 epithelium, after each mitosis, return to a condition, the rest- 

 ing stage between divisions, which resembles that described as 

 'protobroque' by von Winiwarter (fig. 24). It is from this point, 

 after the last 'oogonial division' that the egg-cells in the mouse 

 begin their further development. The cells in this stage are 

 scarcely distinguishable from those in the resting condition 

 between mitoses, and also resemble the 'protobroque' cells of 

 the embryonic proliferation already described, although they 

 may be considerably smaller (figs. 24 and 14). The nucleus is 

 made up of a delicate network or reticulum of chromatin on a 

 Unin frame-work; small clumps or granules of chromatin are 

 located here and there at the intersections of the net-work.- 

 The reticulum may be poorly defined and the granules of chro- 

 matin appear more or less isolated in the nucleus. Two to 

 five nucleoli may be present, although the more usual number 

 is two or three. Flemming's fixation and triple stain, or some 

 similar technique, is necessary to distinguish these nucleoli 

 from the larger clumps of chromatin, with which they may be 

 confused in iron hematoxylin preparations. One nucleolus is 

 usually larger than the others and is sometimes oval or elongated 

 (figs. 28, d and 29, d). 



Stage '6,' (figs. 29 to 33). This stage is marked by a slight 

 increase in size of both oocyte and nucleus. The chromatin 

 granules may increase in size, and the reticulum becomes heavier. 

 There seems to be.an actual increase in the amount of chromatin; 

 as the whole chromatin network is heavier or coarser (figs. 29 

 to 34) from two to five nucleoli may be present, although, as in 

 the preceding stage, two or three seems to be the more usual 

 number. 



Stage 'c,' (figs. 34 to 46). The next phase is marked by a 

 gradual change in the nuclear structure. The whole cell is 

 growing markedly in size and, as the nucleus enlarges, the retic- 

 ulum of chromatin becomes attenuated and loses to a certain 

 degree its character as a network. Apparently the cross-bars 

 break and the chromatin 'flows back' to the longer strands, form- 

 ing threads or strands with granules of chromatin on them (figs. 



