BAUE'S CEITICISMS 313 



on the Galapagos and various other islands, Dr. Gadow * asks 

 the pertinent question — Where did all these creatures come 

 from, and how did they get to these oceanic islands ? Acci- 

 dental transport is out of the question, as land-tortoises are 

 drowned within a few hours after immersion in water. Since 

 none of their kind inhabit the great continents now, although 

 they lived there formerly, we are constrained to assume that 

 the existing species are the survivors of tortoises which pro- 

 ceeded to the islands when they were connected by land with 

 the adjoining continents. In another place Dr. Gadow quotes 

 the Galapagos tortoises as supporting the hypothesis of an 

 Oligocene extension of land, considerably to the west and 

 south of the present Central America. In his maps illus- 

 trating the palaeogeography of Middle America, he actually 

 joins the Galapagos islands with the Antilles, as Professor 

 Baur had done, by way of Cocos island. f 



Professor Boettger J approves of the results obtained by 

 Professor Baur's methods of investigation, arguing that the 

 facts of distribution are much more easily explained by the 

 assumption of a former land connection between the Gala- 

 pagos archipelago and Central America than by the theories 

 hitherto accepted. 



While in general agreement with the same views. Dr. 

 Sarasin § suggests that the ancient land bridge lay in a north- 

 eastward direction, that is to say, from the Galapagos islands 

 towards Mexico rather than to Ecuador. 



The fossil marine mollusks and their distribution' are em- 

 ployed by Dr. von Ihering || in support of the same theory. 

 He draws attention to the remarkable fact that the species 

 of the Tertiary Chilean deposits only appear on the Cali- 

 fornian coast in Pleistocene times, and that similarly the 

 Californian Tertiary forms only reached the coasts of Chile 

 about the same time. On these grounds alone Dr. von Ihering 

 bases his theory of a Tertiary peninsula extending westward 

 into the Pacific Ocean and embracing the Galapagos islands, 



* Gadow, H., " Amphibia and Eeptiles," p. 373. 



t Gadow, H., " Mexican Amphibians and Eeptiles," p. 211. 



X Boettger, 0., " Baur's Differentiation of Species," p. 462. 



§ Sarasin, F., " Die Fauna der Galapagos Inseln," p. 293. 



II Ihering, H. von, " Fauna der Neotropischen Region," p. 296. 



