132 



THE EVOLUTION OF MAN. 



out and draws back again, finger-like processes, thereby ^ 

 modifying its form (Fig. 9). Finally, the young cell has 



Fig. 9. — Active cells from the 

 inflamed eye of a Frog (from the 

 ■watery moisture of the eye, the 

 humor aqueus). The naked cells 

 move freely and creep about ;| 

 like Amcebae and Ehizopods thej 

 accomplish this by extending deli- 

 cate processes from their nakedj 

 protoplasmic bodies. These pro- 

 cesses continually alter in number,! 

 form, and size. The kernel of these] 

 amceboid lymph-cells is not visible,! 

 being covered by the numerous deli- 

 cate granules ■which are scattered! 

 in the protoplasm. (After Frey.) 



feeling, and is more or less sensitive. It performs certain 

 movements on the application of chemical and mechanical] 

 iiTitants. Thus Ave can trace in every single cell all the! 

 essential functions, the sum of which constitute the idea of J 

 life: feeling, motion, nutrition, reproduction. All these' 

 properties which the multi-cellular, highly developed animal 

 possesses, appear in each separate cell, at least in its youth. 

 There is no longer any doubt about this fact, and we may 

 therefore regard it as the basis of our physiological idea of 

 the elementary organism. 



Without lingering here over the extremely interest- 

 ing phenomena of cell-life, we Avill at once attempt to 

 apply the Cell Theory to the egg. The comparison which 

 we have made leads to the important result that we 

 must regard every egg as originally a simple cell. This 

 is of the highest significance, because the whole Science of 



