CHAPTER V. 

 THE EVOLUTION OF LIFE AND MIND 



SOMEWHERE, then, in the primitive Laurentian ocean the 

 earliest definite living things make their appearance. Unless 

 we arbitrarily desert the elementary methods of scientific 

 inquiry, we assume that they were the outcome of a long 

 evolutionary process. We are able to offer several plausible 

 conjectures, even in the present very imperfect state of our 

 knowledge, as to the lines of this evolution. In any case, 

 we see nothing in the simple life of these tiny microbes 

 that forbids us to apply scientific methods to them, and 

 compels us to resign them to the mystic. Science is 

 " bound by the everlasting law of honour," in Lord Kelvin's 

 words, to resist these mystic claims of invasion from an 

 immaterial world as long as natural development is con- 

 ceivable. On that principle Lord Kelvin (then Sir W. 

 Thomson) conjectured that they may have been evolved 

 on some other planet, and carried to ours on a meteorite. 

 That was several decades ago. To-day we realise that our 

 planet may very well have been the original theatre of their 

 appearance. 



The first living things were, of course, of a purely vegetal 

 character. They had no rudiment of locomotory organs, 



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