;68 



EMBRYOLOGY 



Fig. 206, a human ovum is represented in which this change of proto- 

 plasm into deutoplasm is in progress. 



The germinal vesicle lies always in the protoplasmic zone, just out- 

 side of the deutoplasm. As the mass of deutoplasm extends, the 



Protoplasmic Zone 



Corona radiata 



Zona pellucida 



Deutoplasmic Zone 



Germinal Vesicle, 

 with an ameboid 

 germinal Spot 

 Perimtelline Space 



Clear Outer Zone 



Fig. 207. Ovum from a Graafian follicle of a woman thirty years old, X 375 (Nagel). 

 This ovum was taken from a fresh ovary removed from the living subject. 



germinal vesicle is pushed toward the periphery of the vitellus. The 

 vesicle measures about YoW ^ an i nc ^ ( 2 5 to 2 7 /*) m diameter. It is 

 globular, with a double contour. In hardened preparations it presents 

 a frame-work of fine anastomosing fibres. In the fully-developed human 

 ovum, no ameboid movements have as yet been observed in the ger- 

 minal vesicle. In Fig. 207, the germinal vesicle is seen lying upon and 

 not within the deutoplasmic zone. The mature ovum presents but one 

 germinal vesicle. Two germinal vesicles, however, are sometimes found 

 in primordial ova (see Fig. 208). 



