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GENERAL PRINCIPLES 











r'lo. 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; rky and rk>, 

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



