THE BEGINNINGS OF LIFE. 



145 



manner, as the design of the whole requires. This is the 

 fundamental phenomenon of all animal and vegetable 

 vegetation. It is alike equally consistent 'with those instances 

 in which young cells are formed within parent cells^ as 'with 



FIG. 4. 



Animal Cells. 



A. Flattened Epithelium cells from the inside of the mouth. ( x 260.) 



B. Ciliated Epithelium from the human Trachea ; magnified 350 diame- 



ters, a. Innermost part of the elastic longitudinal fibres, b. Ho- 

 mogeneous innermost layer of the mucous membrane, c. Deepest 

 round cells, d. Middle elongated cells, e. Much larger super- 

 ficial cells, bearing cilia, and containing nucleolated nuclei. (K61- 

 liker.) 



those in "which the formation goes on outside of them. The 

 generation of the cells takes place in a fluid or in a 

 structureless substance in both cases x . We will name 



1 There are most important differences between these two modes of 

 cell-formation dependent upon the nature of the material in the midst 

 of which the new units arise. This will be pointed out further on. 



L 



