RELICS OF PRIMEVAL LIFE 



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the earth in the course of geological time ; and 

 as we go back in the record of the rocks, first man 

 himself and, in succession, all the higher animals 

 disappear, until at length in the oldest fossiliferous 

 beds only a portion of the more humble inhabitants 

 of the sea can be found. In the time of the forma- 

 tion of the oldest of these rocks, or perhaps some- 

 what earlier, must have been the first beginning of 

 life on our planet. 



Just as we can trace every individual animal to 

 a microscopic germ in which all its parts were 

 potentially present, so we can trace species, genera, 

 and larger groups of animals to their commencement 

 at different points of the earth's history, and can 

 endeavour to follow the lines of creation or descent 

 back to the first beings in which vital powers mani- 

 fested themselves. All such beginnings must end in 

 mystery, for as yet we do not know how either a 

 germ or a perfect animal could originate from in- 

 -animate matter ; but we may hope at least to make 

 some approximation to the date of the origin of life 

 and to a knowledge of the conditions under which 

 it began to exist, confining ourselves for the present 

 principally to the Animal Kingdom. 



As preliminary to the consideration of this subject, 



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