124 THE THEORY OF EVOLUTION 



Morocco; Italy, Sicily, Malta and Tunis; the Greek 

 islands and the mainland; Japan, Formosa, Borneo, 

 Java, etc., and Asia, and many others. The evi- 

 dences of climatic changes, though of an entirely 

 different kind, are equally clear. 



In brief, the distribution of existing animals and 

 plants constitutes a series of historical problems, 

 the solution of which is to be sought in the facts of 

 geology and palaeontology. On evolutionary prin- 

 ciples, we ought to find that, the longer time any 

 two regions have been separated, the greater is the 

 difference between the animals and plants of those 

 regions, and this is precisely what we do find. So 

 well established is this principle, that we may invert 

 it and use it to distinguish those separations which 

 are earlier from those which are later in geological 

 date, in cases where direct geological evidence is 

 unattainable. The separation of Great Britain from 

 the continent must have taken place very recently, 

 geologically speaking, because there is no important 

 difference between their animals or plants, while the 

 separation of Madagascar from Africa must have 

 been effected at a much earlier time because of the 

 radical differences between the faunas of island and 

 continent. Of course, such instances cannot fairly 

 be used as arguments in favour of evolution, because 

 they assume the truth of the thing to be proved, 

 except in so far as the evolutionary explanation is 

 the only one that will account for the facts. 



Before attempting to explain any of the problems 



