THE METAZOA 



mem 



sey.nud. 



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

 first polar globule; B, beginning of fertilisation, sperms approaching the micropyle or 

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

 tion of the male pronucleus; D, approximation of the male and female pronuclei; E, forma- 

 tion of segmentation-nucleus; 9 cent, female centrosome; $ cent, male centrosome (the 

 centrosomes are cell-structures not further referred to in this work); mem, egg-membrane; 

 microp, micropyle; pol, polar bodies; 9 pron, female pronucleus; $ pron, male pronu- 

 cleus; seg. nucl, segmentation nucleus. 



