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CHAPTER XV. 



GENERAL SUMMARY. 



THE admitted facts of evolution are : 



Life first appeared on the earth in simple 

 forms, and its evolution, as a rule, developed 

 upwards that is, new types as they suc- 

 cessively appeared were more and more fully 

 specialised. 



But to this general rule there are excep- 

 tions, in which a succeeding type was, to a 

 more or less important extent, less highly 

 specialised than its antecessor that is, retro- 

 gressive. 



Evolution proceeded in a main line that 

 ultimately culminated in man, but in its 

 progress many branches sprang from the 

 main stem, and developed until their special- 

 isation also culminated. 



Successive types are in structure and 

 organisation more or less similar to each 

 other. 



Assuming the existence of life in its 



