316 ORIGIN OF LIFE IN AMERICA 



against the theory of a former land connection between the 

 islands and the mainland. He scarcely discusses the problem 

 from a botanical point of view, but assumes that the Gala- 

 pagos islands are of oceanic origin.* 



Personally, I am in agreement with Mr. Andrew Murray's 

 and Professor Baur's theory that the archipelago originated 

 through subsidence of a land-mass which was connected with 

 the mainland. From the latter the islands received the prin- 

 cipal members of the fauna and flora, and these progressed 

 from the one to the other on a solid land surface. Subse- 

 quently, possibly owing to volcanic disturbance, the land sub- 

 sided, leaving only the mountain tops with their animals and 

 plants as fragmentary relicts of a rich and varied fauna and 

 flora. So far I am in agreement with Professor Baur's theory, 

 but I believe that the geological history of the Galapagos 

 archipelago forms only part of a much larger and far more 

 complex problem. In the first place, it is evident that the 

 whole fauna and flora of the Galapagos islands cannot have 

 originated in Central America or the West Indies. A large 

 proportion of the animals and plants seem to have their 

 nearest relations in Ecuador and Colombia. Others point 

 to a still more southern or northern origin. If we derive the 

 fauna and flora principally from a former land connection 

 with the mainland of America, that connection must have had 

 several branches. The affinities of the archipelago appear 

 to be chiefly with Central America and Ecuador and much 

 less with Chile. On the other hand, a certain relationship, for 

 instance among the Bulimuli, exists with the southern ex- 

 tremity of Lower California. All these different areas of 

 North, Central and South America may have been joined 

 with the Galapagos land-mass by peninsulae, though one or 

 more of them may have become disconnected long before the 

 others. Dr. Arldt f indicates something of that kind in his 

 map illustrating the conditions of land and water in Creta- 

 ceous times. At least, he connects western Mexico and 

 Ecuador by a broad land bridge westward of Central America 

 and across the area of the Galapagos archipelago. I ventured 



* Stewart, A., " Botanical Survey of Galapagos Islands," p. 239. 

 t Arldt, J., "Entwicklung der Kontinente," Karte 19. 



