174 The Evolution Hypothesis. 



6. Each physiological unit, in addition to its innate 

 proclivities, has its individual characteristics. These are 

 due to the incidence of environing forces. The history 

 of each unit being different from that of every other, 

 and the incident forces in their impact being diverse 

 in each instance, these diversities involve modifications 

 which give a special peculiarity to each. The unit is 

 inevitably dissolved unless it can adjust its polarity to 

 the new conditions. Its internal equilibration must be 

 brought into accord with the incident forces. Hence 

 the constant change in organisms and the evolution of 

 new forms. If this doctrine be true, we have to clear 

 up a new perplexity. The process of adjustment of 

 units is as difficult to comprehend as the adjustment of 

 living bodies ; and the difficulty is increased by bring- 

 ing into view the further consideration, that while the 

 unit builds up the organism, the organism determines 

 the structure of the unit. Each acts and reacts on the 

 other. Evolution undertakes to elucidate the equili- 

 bration of unit and organic structure, as a means of 

 elucidating the equilibration of the living body and its 

 environment. Is the equilibrium of a system of in- 

 visible molecules more easily determined than the 

 equilibrium of visible masses ? 



7. The physiological units possess inherent powers 

 and properties of the most surprising sort. They 

 have " powers of arranging themselves into the forms 

 of the organism to which they belong." "The 

 polarity of the physiological units produces, during 



