CELLULAR ORGANIZATION OF LIFE 13 



We shall later have occasion to make a study of the details of 

 cell division, known as mitosis, but from what has been said it 

 must occur to the reader that, since cells arise only by division, 

 those of the present day, whether complete free-living organisms 

 or units composing the bodies of higher plants and animals, in- 

 cluding Man, are actually lineal descendants in unbroken series 

 from the beginning of cellular life on the Earth. (Fig. 164.) 



