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. 



