B 



ntenv 



sey.nucl 



FIG. 26 Diagram illustrating the maturation and fertilization of the ovum. A, formation of 

 first polar cell ; B, beginning of fertilization, sperms approaching the micropyle or 

 aperture in the enclosing membrane of the ovum, through which the sperm enters ; 

 C, formation of the male pronucleus ; D, approximation of the male and female pro- 

 nuclei ; K, formation of segmentation nucleus ; 9 cent, female centrosome ; 6* cent, male 

 centrosome (the centrosomes are cell-structures not further referred to in this work) ; 

 mem. egg-membrane ; inicrop. micropyle ; pol. polar bodies ; 9 pron. female pronucleus ; 

 <J Pron. male pronucleus ; scg. nucl. segmentation nucleus. 



