1 st PB 



9 



FIGS. 6-9. SUCCESSIVE STAGES IN THE MATURATION AND FERTI- 

 LIZATION OF THE EGG OF Nereis, less highly magnified than 

 Figs. 6 and 7, showing the progress of the entrance cone (EC) 

 and sperm nucleus (N) into the egg. Fig. 6 shows the first 

 maturation spindle of the egg (1st Mat. Sp.) ; Fig. 7, the first 

 polar body (1st PB) formed by this division; Fig. 8, the sec- 

 ond maturation spindle (2d Mat. Sp.) and the sperm nucleus 

 and spindle (cZV) ; Fig. 9, the division of the male and 

 female nuclei in the first cleavage spindle (1st Cl. Sp.). (From 

 F. R. Lillie.) 



