I 22 



THE EVOLUTION OF MAN. 



present position of the cell theory, and as to the views 

 commonly held in connection with it. 



Fig, 1. — The human egg from the ovary of the female; much enlarged 

 The entire egg is a simple, globular coll. The greater part of the spherical 

 egg- cell is formed by the egg-yelk, or the granular cell-substance (proto- 

 plasm), which is composed of innumerable, delicate yelk-granules, with a 

 little intervening substance. The gerra-vesicle, answering to the cell- 

 kernel (nucleus) lies in the upper part of the yelk. It contains a dark 

 nucleolus or germ-spot. The globular mass of yelk is surrounded by a 

 thick transparent egg-membrane (zona pellucida, or clwrion). This is 

 penetrated by the pore-canals, in the form of very numerous hair-like lines, 

 which run radially towards the centre of the globe ; through these the 

 thread-shaped, moving sperm-cells pass, in the process of impregnation, into 

 the egg-yelk. 



In order rightly to appreciate the Cell Theory, which 



