INTRODUCTORY 



is extruded from the ovum (Fig. 7). The polar bodies are of 

 course minute compared to the egg-cell. The first often divides 

 into two. Thus four cells are produced as in the male, but one 



EUSOT 



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FIG. 7. The maturation divisions in the female (Axolotl). 1, First 

 polar spindle with heterotypic chromosomes ; 2, Extrusion of first polar 

 body ; 3, Appearance of second polar spindle ; longitudinal division of 

 chromosomes in egg and in first polar body ; 4, Second polar spindle radial ; 

 homoeotypic chromosomes on equator (metaphase) ; 5, Polar view of the 

 same ; 6, Ana phase ; 7, Extrusion of second polar body ; 8, Second polar 

 body with resting nucleus ; 9, Female pronucleus in resting condition, 

 closely surrounded by yolk-granules. 



is large, the actual ovum, the others small (potential ova). 

 Each of these four contains, as does each spermatid, only one- 

 half the ordinary number of chromosomes. 



The ripe egg-cell possesses a definite structure, and frequently 

 this structure is polar, as in the case we have been describing, 



