THE GERM CELLS: MITOSIS, MATURATION AND FERTILIZATION 



radially striated membrane, the zona pellucida. The striated appearance 

 of the zona pellucida is said to be due to fine canals which penetrate it 



FIG. i. Human ovum, two- thirds the mature size, examined fresh in the liquor folliculi 

 (Waldeyer). X 415. The zona pellucida is seen as a clear girdle surrounded by the cells of 

 the corona radiata. Yolk granules occupy a central region of the cytoplasm and enclose the 

 nucleus and nucleolus. At the right is a spermatozoon correspondingly enlarged. 



VitelTinc :? 

 membrane 



Zona 

 pellucida 



PIG. 2. Ovum of monkey. X 430. 



and through which nutriment is transferred from smaller follicle cells 

 to the ovum during its growth within the ovary. The origin and growth 

 of the ovum within the ovary (oogenesis) are described on pp. 216-218. 



