CHAPTER XI 



THE PROGRESSIVE DEVELOPMENT OF THE LIFE-WORLD, 

 AS SHOWN BY THE GEOLOGICAL RECORD 



IN order to form any adequate conception of the world of 

 life as a whole, of the agencies concerned in its development, 

 and of its relation to man as its final outcome, we must 

 endeavour to learn something of its past history ; and this 

 can only be obtained by means of the fossilised remains 

 preserved in the successive strata or layers of the earth's 

 crust, briefly termed " the geological record." In the pre- 

 ceding chapter I have endeavoured to indicate the forces 

 that have been at work in continually moulding and remould- 

 ing the earth's surface ; and have argued that the frequent 

 changes of the physical environment thus produced have 

 been the initial causes of the corresponding changes in the 

 forms of organic life, owing to the need of adaptation to the 

 permanently changed conditions ; and also to the opening 

 up of new places in the economy of nature, to be successively 

 filled through that divergency of evolution which Darwin so 

 strongly insisted upon as a necessary result of variation and 

 the struggle for existence. 



But in order to appreciate the extent of the changes of 

 the earth's surface during the successive periods of life- 

 development, it is necessary to learn how vast, how strange, 

 and yet how gradual were those changes ; how they consisted 

 of alternate periods of not only elevation and depression, 

 but also of alternations of movement and of quiescence, the 

 latter often continuing for long periods, during which more 

 and more complete adaptation was effected, and, perhaps in 

 consequence, a diminished preservation in the rocks of the life 

 of the period. Thus have occurred those numerous " breaks " 



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