146 THE STORY OF THE LIVING MACHINE. 



impossible to avoid the conclusion that such a 

 nation with such a history did actually exist. 

 Two independent sources of record could not be 

 false in regard to such a matter as this. 



Now, our sources of evidence for this history 

 of the living machine prove to be of exactly this 

 kind. We have three independent sources of 

 evidence which are so entirely different from 

 each other that there is almost no likeness be- 

 tween them. One is written in the rocks, one in 

 bone and muscle, while the third is recorded in 

 the evanescent and changing pages of embry- 

 ology and metamorphosis. Yet each tells the 

 same story. Each tells of a history of this ma- 

 chine from simple forms to more complex. Each 

 tells of its greater and greater differentiation of 

 labour and structure as the periods of time passed. 

 Each tells of a growing complexity and an in- 

 creasing perfection of the organisms as successive 

 periods pass. Each tells us of common points of 

 origin and divergence from these points. Each 

 tells us how the more complicated forms have 

 arisen as the results of changes in and modifi- 

 cations of the simpler forms. Each shows us 

 how the individual parts of the organisms have 

 been enlarged or diminished or changed in shape 

 to adapt them to new duties. Each, in short, tells 

 the same story of the gradual construction of the 

 living machine by slow steps and through long 

 ages of time. When these three sources of his- 

 tory so accurately agree with each other, it is as 

 impossible to disbelieve in the existence of such 

 history as it is to disbelieve in the existence of 

 the ancient Hittite nation, after its history has 

 been told to us by two different sources of record. 



Now all this is very germane to our subject. 



