EVIDENCES OF EVOLUTION 19 



this lizard, ftf^ *h*** " nf " a single is1fl.nf| con- 



tained more than one race or specie. . Thpi.^ 

 same Is true of the tortoises and the birds, 

 and no scientific interpretation has been 

 suggested except that which Darwin gave of 

 divergent evolution from a common stock. 



We cannot here enter into a discussion of 

 the geological history of the Galapagos Islands, 

 in regard to which there is some difference of 

 opinion; it must suffice to state one of the 

 theories that advanced by Baur in the Woods 

 HoJL Biplogj^Ll Lectures "for 1894. "At a 

 former period these islands were connected^ 

 with each other, forming a single large island, 

 which itself at a still earlier time was united 

 with the continent, probably with Central 

 America and the West Indies. When this 

 large island was not yet broken up into a 

 series of smaller islands, the number of species 

 must have been very much smaller; probably 

 there was only one species of Nesomimus, of 

 Certhidia, of Tropidurus, of the Land Tor- 

 toise, and so on. JThr^ughJsoIation into single 

 islands the peculiar differentiation of the 

 species began; an originally single species was 

 differentiated in many different forms; every, 

 or nearly every, island developed its peculiar 

 races. IVestill see to-day that islandsjvhigb, 

 are closetogelher and not sefrarate7Tb}Tdeep 



