OOGENESIS IN THE WHITE MOUSE 303 



9. Mitochondria, which, although granular in the developing 

 definitive oocytes, are also found as rods or threads in the germ 

 cells and frequently appear in all forms in the follicle cells, are 

 not to be considered characteristic of the germ cells. Certainly 

 no one particular form is constant in the germ cells, a condition 

 which is not surprising when one considers the probable nature 

 of the mitochondj-ia and the different methods for demonstrating 

 them. 



10. The new formation of germ cells from the germinal epithe- 

 lium is prolonged and extends from birth or shortly afterwards 

 to approximately sexual maturity. This prolonging of the poten- 

 tiality of the germinal epithelium for germ cell production and 

 the absence of 'cell-cords' are probably to be correlated with the 

 small size of the ovary of the mouse. 



11. Synizesis is found constantly in the development of the 

 primitive oocytes; while in the differentiation of the definitive 

 ova, neither synizesis nor synapsis occur. In the case of the 

 primitive germ cells, which are fated to degenerate, the sug- 

 gestion is repeated that synizesis may represent a stage in de- 

 generation, wherein the normal relations of nucleus and cyto- 

 plasm, and thp forces governing them are disturbed. The fact 

 that similar stages have been found in somatic cells militates 

 against the attributing of any special genetic significance to 

 these conditions. ' 



12. The evidence shows that all the primitive oocytes (embry- 

 onic proliferation) develop to a certain extent and then degener- 

 ate. This is accomplished by the time the mouse is sexually 

 mature. 



I wish to acknowledge my indebtedness to the Department of 

 Histology and Embryology for materials and facilities for work. 

 I also desire to express my appreciation of the kindness and 

 encouragement of Dr. B. F. Kingsbury whose interest and 

 criticism have been of great assistance to me in this study. 



