iftern 



qpro/t 



se^.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 t forma- 

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

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

 microp, micropyle; fiol, polar bodies; $ fron, female pronucleus; $ Pron t male pronu- 

 cleus; seg. ttucl, segmentation nucleus. 



