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THE EVOLUTION OF MAN. 



present position of the cell tlieory, 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 cell. 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 innumei^able, delicate yelk-granules, with a 

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

 kernel (nucleus) lies in the Tipper 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 cliorion). 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 

 thi'ead-shaped, moving sperm-cells pass, in the process of impregnation, into 

 the egg-yelk. 



In order rightly to appreciate the Cell Theory, which 



