ORGANIC E VOL UTION. 23 



guiding principle of scientific classification is the 

 comparing of organism with organism, with the 

 view of seeing which of the constituent organs 

 are of the most invariable occurrence, and 

 therefore of the most typical signification. 



Now, since the days of Linnaeus this principle 

 has ^been carefully followed, and it is by its aid 

 that the tree-like system of classification has 

 been established. No one, even long before 

 Darwin's days, ever dreamed of doubting that 

 this system is in reality, what it always has been 

 in name, a natural system. What, then, is the 

 inference we are to draw from it ? An evolu- 

 tionist answers, that it is just such a system as 

 his theory of descent would lead him to expect 

 as a natural system. For this tree-like system is 

 as clear an expression as anything could be of 

 the fact that all species are bound together by 

 the ties of genetic relationship. If all species 

 were separately created, it is almost incredible 



