THE GERM CELLS 



FIG. 2.- Diagrammatic longitudinal section of an un- 

 incubated hen's egg (after Allen Thomson, in Heisler). 

 (Somewhat altered) : b.l, germinal area; w.y, white yolk, 

 which consists of a central flask-shaped mass, and a num- 

 ber of concentric layers surrounding the yellow yolk 

 (y.y.)', v.t, vitelline membrane; x, a somewhat fluid al- 

 buminous layer which immediately envelops the yolk; 

 w, albumen, composed of alternating layers of more and 

 less fluid portions; ch.l, chalazae; a.ch, air-chamber at 

 the blunt end of the egg simply a space between the two 

 layers of the shell-membrane; i.s.m, inner, s.m, outer 

 layer of the shell-membrane; s, shell. 







FIG. 3. Section of human ovary, 

 including cortex; a, germinal epithel- 

 ium of free surface; b, tunica albugi- 

 nea; c, peripheral stroma containing 

 immature Graafian follicles (d); e, 

 well-advanced follicle from whose wall 

 membrana granulosa has partially 

 separated; /, cavity of liquor folli- 

 culi; g, ovum surrounded by cell-mass 

 constituting cumulus oophorus (Pier- 

 sol). 



FIG. 4. Section of well-developed Graafian follicle FIG. 5. Ovary with mature Graafian 



from human embryo (von Herff); the enclosed ovum follicle about ready to burst (Ribemont- 

 con tains two nuclei. Dessaignes). 



