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THE SURVIVAL OF THE FITTEST 



WHAT constitutes fitness? There can hardly be a 

 more important question. Our answer to it will 

 color our view of the whole theory of evolution and 

 of life. 



One or two characteristics of fitness are fundamental, neces- 

 sary, and evident at the outset. The fittest must be pro- 

 gressive. However great its attainments, if it halts in its 

 progress, it will surely be surpassed and left behind by some 

 steadily advancing form, and progress must be continued 

 through a long series of generations, hence the fittest must 

 be tough, vigorous, tenacious of life. But a host of forms 

 seem able to meet these two requirements. 



How can we sift them? We might accept the great line of 

 progress marked out by the logic of evolution. But it is 

 safer and more profitable to notice the facts furnished by ge- 

 ology and palaeontology. We will attempt to catch a glimpse 

 of our globe at various stages of evolution, and see what 

 forms are competing for the prize of survival and leadership in 

 the struggle for life. As we pass from stage to stage, we can 

 mark the success or failure of the experiments tried by the 

 most promising competitors in preceding stages. 



There was life on the globe long before the beginning of 

 Palaeozoic time. The " everlasting hills " have slowly risen, 

 grown old, worn down and disintegrated, often almost dis- 

 appeared, since bacteria and many less primitive forms came 

 on the stage. Life antedates and outlasts them all. But the 

 earliest forms of life were mostly soft-bodied and left no trace. 

 The few earliest remains teach us little. We catch our first 



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