EVIDENCES OF EVOLUTION. 125 



find different productions; though as mountain 

 chains, deserts, etc., are not as impassable, or likely 

 to have endured so long as the oceans separating 

 continents, the differences are very inferior in degree 

 to those characteristic of distinct continents.'* ' 



An instructive illustration of the matter under 

 discussion is afforded by Darwin, in his observations 

 on the flora and fauna of the Galapagos Archipel- 

 ago. This is a group of islands situated between 

 five and six hundred miles west of South America, the 

 constituent islands being separated from one another 

 by straits from twenty to thirty miles in width. 

 " Each separate island of the Galapagos Archipel- 

 ago," says the great naturalist, " is tenanted, and the 

 fact is a marvelous one, by many distinct species ; 

 but these are related to each other in a very much 

 closer manner than to the inhabitants of the Ameri- 

 can continent, or of any other quarter of the world." * 



From observations made by naturalists all over 

 the world, it is learned that the foregoing is but one 

 of countless similar instances that might be adduced. 

 Hence the general conclusion reached by the dis- 

 tinguished German savant, Moritz Wagner, that "the 

 limits, within which allied species are found, are de- 

 termined by impassable natural barriers." 



Pacts of Geological Succession. 



It is only, however, when we come to compare 

 the facts of geographical distribution with those of 

 geological succession, that we are able to appreciate 



1 Darwin's " Origin of Species," vol. II, pp. 130-131. 

 a Op. cit., vol. II, p. 190. 



