300 ORIGIN OF LIFE IN AMERICA 



Lasiurus has likewise succeeded in reaching one other group 

 of islands besides the Galapagos archipelago, namely the 

 Sandwich islands. The latter are inhabited by Lasiurus 

 semotus, which is peculiar to them, and cannot therefore be 

 considered as a recent human importation. 



Our present knowledge of the mammalian fauna of the 

 Galapagos islands has added one factor of extreme importance 

 to those hitherto known, namely the certainty that there are 

 indigenous mammals on the archipelago. For this reason the 

 Galapagos islands should be excluded from the oceanic 

 islands, and be placed among the islands which once formed 

 part of a larger land-mass or continent. It is not certain, 

 however, that Darwin and Wallace would have taken that view, 

 even had they been convinced that the mammals alluded to 

 were truly indigenous in the islands. Some naturalists hold 

 that even mammals can be successfully transported across 

 the ocean on tree trunks and floating islands. Dr. Stearns,* 

 in alluding particularly to the Galapagos fauna, remarks 

 that a single tree of large size might carry with it not only 

 molluscan and insect life, but also living individuals of many 

 vertebrate forms that found refuge or safety upon it. Thus, 

 he continues, if the environmental conditions were at all 

 favourable, colonies of many animal forms could be trans- 

 planted to distant regions. ' The possibility of such an acci- 

 dental transportal must have been carefully considered and 

 rejected by Darwin and Wallace. The Humboldt current I 

 alluded to as striking the Galapagos islands does not come 

 from the coast of Ecuador nor from Central America. It 

 originates in the far south, and, passing northward, skirts the 

 coast of Chile and southern Peru, and then leaves the land in a 

 north-westward direction. The tree trunks spoken of by Dr. 

 Stearns as carriers of all kinds of animal life would have had 

 to travel several thousand miles, no doubt experiencing stormy 

 weather on the way, before they could have safely deposited 

 their loads of vertebrates on the shores of the Galapagos 

 islands. If these floating trees are responsible for the present 

 mammalian fauna of these islands, how is it that they have 

 brought nothing new to them since their occupation by man ? 



* Stearns, E. E. C., " Mollusk-fauna of the Galapagos Islands," p. 366. 



