296 OKIGIN OF LIFE IN AMEKICA 



with a number of ancient types of animals and plants. In the 

 Galapagos islands similar relicts of bygone ages are found, yet 

 their presence on the islands is not generally considered to 

 be due to a former land connection with the mainland. Bub 

 the question whether the animals and plants inhabiting this 

 archipelago are the descendants of purely accidental visitors 

 or not, is of more than usual importance in this case. Both 

 Mr. Darwin and Dr. Wallace expressed the opinion that the 

 Galapagos islands are of the oceanic type, and that they 

 originated from sub-oceanic volcanoes, having never formed 

 part of a continent or any large land-mass. Many of the more 

 recent observers have followed the lead of our two great 

 naturalists. I need only mention Professor Agassi/, Dr. 

 Wolf, Mr. Salvin, Dr. Dall and Dr. Stearns. On the other 

 hand, Professor Baur was the first to seriously contest the 

 view of these authorities. His researches led to a reconsidera- 

 tion of the problem presented by the fauna and flora of the 

 Galapagos islands and a rejection by many naturalists of the 

 theory so ably maintained by Darwin and his followers. 



Islands, as I have already indicated, possess many advan- 

 tages over continental areas for the study of the laws and 

 phenomena of distribution. The islands we are now dealing 

 with, moreover, are of the most profound importance in con- 

 nection with the geological history of the two great American 

 continents. We might almost say that the problem of 'the 

 Galapagos fauna presents the key to the solution of the most 

 complex and intricate questions concerning the American 

 fauna with which we are confronted. It is for this reason 

 that the whole of this chapter will be devoted to an exhaustive 

 survey of the Galapagos islands and their inhabitants. 



When Darwin landed on the archipelago in 1835, he noted 

 in the first instance the fact that all the islands were formed 

 of volcanic rock and that they contained numerous craters. 

 The craters he found to consist either of lava and scoriae, or 

 of finely -striated sandstone-like tuff. All the latter, which he 

 examined, had the southern sides either much lower than the 

 other sides, or quite broken down and removed. He concluded 

 from this fact that all these craters were formed beneath the 

 sea, and that their broken state was due to the action of the 

 waves produced by the southern trade winds. On the other 



