THE ARGUMENT FROM PALAEONTOLOGY 57 



Ammonites are characteristic secondary forms, and 

 are very abundant, but none survive into the Tertiary 

 period. The Ichthyosaurus, Plesiosaurus, and 

 Mosasaurus are extremely characteristic, and confined 

 to the Secondary period. 



(3) The Primary or Palaeozoic Period. — Here 

 we find fossil plants in the Coal measures, the Lepido- 

 dendron, Catamites, Sigillaria, and Stigmaria. Fish 

 are also found abundantly. The Trilobites are exclu- 

 sively Palaeozoic ; also the Sea-scorpions, Pterygotus, 

 and Eiirypterus. 



The general conclusions we arrive at are : 



(1) There is a general advance in organisation 

 from the lower to the higher or more recent deposits, 

 and an increase in the diversity of type. 



(2) There is no evidence of sudden breaks or 

 cataclysms ; there is no break between the Tertiary 

 period and the present day. Some species die out 

 and others appear, and some persist unchanged. 

 The very evidence which Cuvier relied on to prove 

 jCatastrophism disproves it when examined more 

 carefully and with fuller knowledge. 



(3) Some forms, known as persistent types, remain 

 unchanged for great periods. This constitutes no 

 real difficulty, for Natural Selection does not of 

 necessity involve progression or change of any 

 kind, and is quite consistent with a stationary con- 

 dition, provided that the environment, or at least 

 all the features of the environment affecting them, 

 remain unchanged. These are examples of the 

 real aristocracy of animals, for they can date back 

 their descent not merely to the time of the appearance 



