CHAPTER XI 



THE PAST AND THE PRESENT 



ONE of the most striking and important facts 

 which has been established through a study 

 of the fossil animals is that from the very- 

 earliest times, from the very first beginnings of the 

 fossil record, the broader aspects of the animal life 

 upon the earth have remained unchanged. 



When we examine a series of fossils of any age we 

 may pick out one and say with confidence "This is a 

 crustacean" — or a starfish, or a brachiopod, or an 

 annelid, or any other type of creature as the case 

 may be. 



In the details of their structure these fossils are not 

 necessarily like the crustaceans, starfishes (fig. 41, 

 p. 71), brachiopods (fig. 60, p. iii), annelids (fig. 85, 

 p. 161) or other creatures living in the present seas. 

 Nevertheless, if they are sufficiently well preserved we 

 have no difficulty in recognizing at once the group to 

 which each and every fossil animal belongs. 



How do we recognize these fossils as members of 

 the various groups? We are able to recognize them 

 because they fall within the definition of a particular 

 group. But the definitions of the phyla or major 

 groups of animals are all drawn up on the basis of a 

 study of their living representatives alone. 



Since all the fossils are determinable as members of 

 their respective groups by the application of defini- 



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