] 'nets and /•'actors of Development 



9 



Memb 



^> 



B 



Fig. 2. A nearly Ripe Human Ovum in the Living Condition. The 

 ovum is surrounded by a series of follicle cells (FC) inside of which is the 

 clear membrane (Memb.) and within this is the ovum proper containing 

 yolk granules (F) and a nucleus (A r ) embedded in a clear mass of prdto- 

 plasm. Magnified 500 diameters (x 500). (From O. Hertwig.) B, two 

 human spermatozoa drawn to about the same scale of magnification. 

 (After G. Retzius.) 



new organisms, of cells to give rise to other cells, and of parts of 

 cells to give rise to similar parts by the process of division. 



(d) Irritability, or the capacity of receiving and responding to 

 impinging energies, or stimuli, in a manner which is usually, but 

 not invariably, adaptive or useful. 



Germ Cells Alive. — Both the egg and the sperm are living cells 



