FERTILIZATION OF OVUM IN WHITE MICE. 



315 



interior (Fig. 182), with irregular chromatin masses. It continues to grow more 

 and more, and develops at the same time a series of nucleoli more or less uniform 

 in size. This stage may be regarded as that of the completed female pro-nucleus. 



Fig. 181. — Ovum of White Mouse, after the 

 Formation of the Polar Globule. Both 

 Pro-nuclei are Present. X 5°° diams. — 

 {After J. Sobotta.) 



Fig. 182. — Ovum of White Mouse, with Two 

 Well-developed Pro-nuclei. X 5°° diams. 

 —{After J. Sobotta.) 



Fertilization. — As the general account of the fertilization or impregnation 

 of the mammalian ovum is based on the process in the white mouse, it is neces- 

 sary only to refer to descriptions and figures, pages 49 to 54. 



