Animals Before Man 



years. On the otlier hand, none of the mam- 

 mals now living are at all nearly related to 

 those that flourished during the period of time 

 we call Eocene, while few, indeed, are to be 

 found even in the Pliocene. And that mam- 

 mals should have changed more rapidly than 

 any other animals is only w^hat might have 

 been expected from their high organization, as 

 this should theoretically render them particu- 

 larly susceptible to changes going on about 

 them. 



It may be noted that each of the groups of 

 animals that successively made their appearance 

 had its culminating point, its high-water mark, 

 when it was most numerous in species and indi- 

 viduals. This point reached, sooner or later the 

 tide of life receded, sometimes, indeed, carrying 

 the race quite out of existence. 



For a time after the appearance of any new 

 group of animals it seems to make little prog- 

 ress, lying dormant as it were, and then sud- 

 denly branches out in various directions. It 

 will be remembered how through two entire 

 periods, the Jurassic and Cretaceous, the mam- 



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