246 H. M. KINGERY. 



Up to this point oocytes in follicles undergoing follicular 

 atresia have passed through the same stages, with some dif- 

 ferences in detail, as normally maturing egg-cells. The later 

 stages however are different. The next step in degeneration is 

 the breaking down of the spindles. The usual course is for the 

 oocytes to form the second polar spindles which then break down ; 

 but if degeneration has proceeded a little more rapidly, this fate 

 ma} 7 overtake the first polar spindles before the polar body is 

 formed. 



As stated above, in the first polar spindle as well as in the 

 second, the achromatic fibers are all intermingled, those with 

 chromosomes attached and those without, and do not differ in 

 appearance or staining reaction. The fibers with no chromo- 

 somes attached to them break across at their middle and the 

 free ends move out in the cytoplasm. As the polar ends remain 

 attached to the poles of the spindles, the formation of "asters" 

 is brought about. Stages are seen (Figs. 5 and 6) in which the 

 breaking or splitting off of the fibers is taking place; some of 

 the fibers have just broken across, in the figures, and others have 

 already assumed a radial position, giving the appearance of 

 "asters." The achromatic fibers with chromosomes attached 

 next break or split off, and as their free ends move out into the 

 cytoplasm, they draw after them the attached chromosomes 

 (see Fig. 7). In this way more fibers are added to the, "asters" 

 and chromosomes are seen connected with the ends of some of 

 the fibers. This splitting off of the achromatic fibers explains 

 the fact that some spindles have radiating fibers or "asters" at 

 their poles, while in others they are absent. ^ The oocytes con- 

 taining spindles without radiating fibers have not advanced so 

 far in degeneration that the spindle fibers have begun to split off. 

 The result of this splitting off of the fibers and the consequent 

 breaking down of the spindles is that the chromosomes are 

 scattered in all directions in the cytoplasm at each pole of the 

 spindle, while still connected with the poles by the spindle fibers. 



The cause of the breaking down of the spindles is to be found 

 in the degeneration of the oocyte. That this degeneration has 

 proceeded to quite an extent is shown by the presence in the 

 cytoplasm of fat-granules and crystalloid bodies, and by the 



