THE CELL AND PROTOPLASM. 73 



one of mechanical evolution. It is plain then 

 that the question of whether we can attribute the 

 properties of the simplest type of life to chemical 

 composition or to mechanical structure is more 

 than a formal one. 



TH3 DISCOVERY OF CELLS. 



It is difficult for us to-day to have any 

 adequate idea of the wonderful flood of light 

 that was thrown upon scientific and philo- 

 sophical study by the discoveries which are 

 grouped around the terms cells and proto- 

 plasm. Cells and protoplasm have become so 

 thoroughly a part of modern biology that we can 

 hardly picture to ourselves the vagueness of 

 knowledge before these facts were recognized. 

 Perhaps a somewhat crude comparison will illus- 

 trate the relation which the discovery of cells 

 had to the study of life. 



Imagine for a moment, some intelligent being 

 located on the moon and trying to study the 

 phenomena on the earth's surface. Suppose that 

 he is provided with a telescope sufficiently power- 

 ful to disclose moderately large objects on the 

 earth, but not smaller ones. He would see cities 

 in various parts of the world with wide differ- 

 ences in appearance, size, and shape. He would 

 see railroad trains on the earth rushing to and 

 fro. He would see new cities arising and old 

 ones increasing in size, and we may imagine him 

 speculating as to their method of origin and the 

 reasons why they adopt this or that shape. But 

 in spite of his most acute observations and his 



