mcfrv 



5 ptort 



se^.fuuZ 



Fig. 140. The maiui-ation and iinj>regnation of the animal ovum (diagrammatic). 



A, the ovum, surrounded by the vitelline membrane ijnem\ in the act of forming 

 the first polar cell (Poi); ^ cent, centrosome. B, both polai- cells (pof) are 

 formed, the female pronucleus (9 /n?/^.) lies near the centre of the ovum, and 

 one of the several sperms is shown making its way into the ovum at the micropyle 

 (^inicrof). C, the head of the sperm has become the male pronucleus {h pron\ 

 Its intermediate piece the male centrosome (cJ cent) \ other structures as before. 

 p, the male and female pronuclei are in the act of conjugation. E, conjugation 

 is coinpletc, and the segmentation nucleus {^seg. lutcl) formed. (From Parker 

 and Haswell's Zoology.') 



