SO-CALLED PARTHENOGENESIS IN THE WHITE MOUSE. 247 



fact that the cytoplasm stains much more deeply with acid stains 

 such as eosin and orange G than does the cytoplasm of normal 

 oocytes. The spindle fibers share in this degeneration and show 

 it first by breaking across and splitting off from the spindle. 

 Rubaschkin states that as the fibers split off, the poles of the 

 spindles approach each other and finally come to lie so close 

 together that it is difficult or impossible to distinguish one from 

 the other. While this account of the breaking down of the 

 spindles agrees essentially with that of Rubaschkin for the 

 guinea-pig, nothing resembling the approach of the poles of the 

 spindles was observed in the mouse. 



The achromatic fibers soon disappear and the chromosomes 

 thus left free in the cytoplasm of the oocyte begin to form 

 nuclei. Each chromosome forms a small vesicle which has the 

 appearance of a vacuole with the chromatin material massed at 

 one side (Fig. 13). In some instances the chromatin is arranged 

 in small granules around the outer part of the vesicle (Fig. 8). 

 As this process goes on, the vesicles near enough together coalesce 

 to form larger ones (Figs. 8, 9, n), while those isolated in the 

 cytoplasm remain separate. In this way a varying number of 

 nuclei are formed, of different sizes. A nucleus formed by the 

 combining of a number of chromosomes is larger than one formed 

 from a single chromosome. The final number of nuclei thus 

 formed may be from two to twelve, depending on how the 

 chromosomes were scattered in the oocyte. These nuclei are 

 transformed into resting nuclei of more or less normal appearance. 



The nucleo-cytoplasmic relationship, already interfered with 

 by the degenerative changes in the egg-cell, is further disturbed 

 by this formation of a number of small nuclei. The size-relation- 

 ship, as well as the morphological, physiological, and chemical, 

 relationship, is clearly affected. Apparently there is an effort, 

 even in the degenerating oocyte, to restore as far as possible chis 

 size-relationship, and this effort is expressed by a breaking up 

 of the cytoplasm into smaller parts around the various nuclei. 

 A part of the cytoplasm may surround several of these small 

 nuclei when these are close together, or may enclose only one, 

 when they are isolated. It occasionally happens that a bit of 

 the cytoplasm may fail to contain even one of these nuclei, when 



