THE GERM CELLS 



*9 



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 

 (v.y.); i 1 .', 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, chalaza:; 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; 6, 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). 



M ■ Ktfm 



1 M, 



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- 

 contains two nuclei. Dessaignes). 



