250 H. M. KINGERY. 



which in the early stages at least resemble maturation. That 

 these changes are in some way correlated with the atresia is 

 shown by the fact that all the oocytes exhibiting these phenomena 

 are found in atretic follicles, and egg-cells of normal appearance 

 are seen in the follicles not yet overtaken by atresia. The 

 degeneration of the follicle stimulates the oocyte to pass through 

 a process which at first resembles maturation but which later 

 results in a breaking up of the egg-cell into fragments, some with 

 nuclei and some without. In the light of the evidence here pre- 

 sented, this process can not be considered parthenogenetic 

 cleavage for no mitotic figures other than those of a more or less 

 abnormal maturation were seen; and if this were true partheno- 

 genetic cleavage it would be expected that some stages of mitosis 

 would be observed. The absence of mitotic figures other than 

 more or less normal polar spindles, the breaking down of these 

 spindles, the scattering of the chromosomes, the formation of 

 nuclei from these chromosomes, and the consequent breaking up 

 of the egg-cell into small parts, with or without nuclei, show 

 rather conclusively that in the white mouse, not yet sexually 

 mature, the process is one of degenerative fragmentation. 



SUMMARY. 



The spindles seen in oocytes in follicles undergoing atresia 

 folliculi are maturation spindles, more or less abnormal, and not 

 cleavage spindles. 



By the splitting off of the achromatic fibers and the consequent 

 breaking down of these spindles the chromosomes are scattered 

 through the cytoplasm of the oocyte and form a number of nuclei. 



The nucleo-cytoplasmic relationship, disturbed by the de- 

 generative changes in follicle and egg-cell, causes the oocyte to 

 break up into fragments, some with one or more nuclei and some 

 with none. These fragments are gradually absorbed, probably 

 through the action of phagocytic cells of follicular origin, and 

 disappear. 



The process is one of degenerative fragmentation and not 

 parthenogenetic cleavage. 



