12 



Dynamic Theory. 





FIG. 14. Sperm cells (male cells). 

 M. Human. 



K. Rabbit. 



H. Mouse. 



1. Broad side of cells. 



2. Edge of cells. 



&.-Head. 



in. Central protoplasm. 



*. Tail. 



FIG. 17. 



FIG. 18. 



FIG. 15. Human egg not impregnated, z. Zona pellucida or egg membrane cover 

 full of pores, through which the sperm cells penetrate, y. Central part of egg full of 

 nutritive protoplasm, n. Nucleus or germ vesicle within which is seen the nucleolus 

 or germ spot. 



FIG. 16. Fertilized egg cell of mammal (rabbit). Germ vesicle or nucleus has disap- 

 peared. Outside membrane is modified, a mucous albuminous layer (h) being deposited 

 on the outside of (z) zona pellucida. d. Inside yelk or protoplasm, s. Supernumerary 

 disappointed sperm cells. 



Fig. 17. Parent cell (cytula) of rabbit, after the formation of the nucleus (&) andnucle- 

 olus (n). 



Fig. 18. First cleavage of the foregoing into two cells, e. Bright cell, mother of the 

 future skin layer, i. Dark cell, mother of the future intestinal layer, s. Dead sperm 

 cells. 



