10 Can Science Explain Life? 



bodies, never conjugate, and never develop into 

 multicellular organisms. 



The existence of a definite gap in size between 

 the smallest nucleated cells and the largest bac- 

 teria indicates that bacteria represent a distinctly 

 different form of life from nucleated cells, and 

 when we consider the extreme simplicity of their 

 forms and the homogeneity of their internal struc- 

 tures we feel inclined to believe that they consti- 

 tute the most primitive class of living organisms. 

 Even the largest of them are not far above the 

 limit of microscopic vision, and there is every 

 reason to believe that there are innumerable 

 species which are similar in form and constitution 

 to their larger representatives, but which are too 

 small for the microscope to reveal. 



In order to avoid a confusion of issues at the 

 outset, we shall for the present confine our atten- 

 tion as much as possible to the bacteria because 

 these exhibit the fundamental life processes in 

 their simplest phases. The problem of explain- 

 ing life does not require that we should furnish an 

 explanation of the entire process of evolution, but 

 only of those processes and characteristics which 

 are common to all forms of life and which must 

 have been exhibited by the most primitive form of 

 living matter as it first appeared on this earth. 



