THE THEORY OF EVOLUTION IN 

 THE LIGHT OF FACTS. 



SECTION /. 



GENEKAL (PAL^EONTOLOGICAL) BASES OF THE THEOEY 

 OF EVOLUTION. 



CHAPTEE I. 



OKIGIN OF THE PROBLEM AND DEFINITION OF 

 QUESTIONS INVOLVED. 



1. Origin of the problem. 



A STUDY of the organic world in which we live demon- 

 strates clearly that the animals and plants do not show 

 a confused admixture of forms but display a separation 

 into groups which can usually be defined with sufficient 

 certainty. We find individuals which among them- 

 selves are fairly alike in all characters and which under 

 normal circumstances can also only be perfectly fertile 

 by intercrossing. The whole of these individuals which 

 are so related to each other form a so-called systematic 

 species. The Wolves, for instance, form such a species 

 (Canis lupus L.). That by the word ' wolf ' we represent 

 a defined type of animal which cannot be confounded 

 with another is shown by the pictures in our school- 

 books and primers by which the children are made 



