XIII EVOLUTIOX 221 



does the whole thing depend upon the fancy of the classi- 

 fiers, like the arrangement of books in a library ? In other 

 words, are all possible classifications of living things more 

 or less artificial, or is there such a thing as a natural 

 classification ? 



Suppose we were to try and classify all the members of a 

 given family — parents and grandparents, uncles and aunts, 

 cousins, second cousins, and so on. Obviously there are a 

 hundred ways in which it would be possible to arrange 

 them — into dark and fair, tall and short, curly-haired and 

 straight-haired, and so on. But it is equally obvious that 

 all these methods would be purely artificial, and that the 

 only natural way, i.e., the only way to show the real con- 

 nection of the various members of the family with one 

 another would be to classify them according to blood- 

 relationship ; in other words, to let our classification take the 

 form of a genealogical tree. 



There are two theories which attempt to account for the 

 existence of the innumerable species of living things which 

 inhabit our earth : the theory of special creation and the 

 theory of evolution. 



According to the theory of creation, all the individuals 

 of every species existing at the present day — the tens of 

 thousands of dogs, frogs, oak-trees, and what not, are 

 derived by a natural process of descent from a single indi- 

 vidual, or from a pair of individuals — in each case precisely 

 resembling, in all essential respects, their existing descend- 

 ants — which came into existence by a process outside the 

 ordinary course of nature and known as creation. On this 

 hypothesis each species of frog is derived from a common 

 ancestral pair which came into existence, independently of 

 the progenitors of all the other species, at some previous 

 period of the earth's history. 



