326 



GENERAL PRINCIPLES 







< 



FIG. 187. Six stages in the process of fertilization of the ovum of a mouse. 

 After the first stage figured it is impossible to determine which of the two nuclei 

 represents the male or female pronucleus. ek. Female pronucleus; rk\ and rk*, 

 polar globules; spk, male pronucleus. (McMurrich from Sobotta.) 



