420 CHARLES DARWIN 



dane or widely distributed genus, has here eight species, of 

 which seven are confined to the archipelago, and not one 

 found on any two islands : Acalypha and Borreria, both mun- 

 dane genera, have respectively six and seven species, none 

 of which have the same species on two islands, with the 

 exception of one Borreria, which does occur on two islands. 

 The species of the Compositae are particularly local ; and Dr. 

 Hooker has furnished me with several other most striking 

 illustrations of the difference of the species on the different 

 islands. He remarks that this law of distribution holds good 

 both with those genera confined to the archipelago, and those 

 distributed in other quarters of the world: in like manner 

 we have seen that the different islands have their proper spe- 

 cies of the mundane genus of tortoise, and of the widely 

 distributed American genus of the mocking-thrush, as well 

 as of two of the Galapageian sub-groups of finches, and 

 almost certainly of the Galapageian genus Amblyrhynchus. 



The distribution of the tenants of this archipelago would 

 not be nearly so wonderful, if, for instance, one island had 

 a mocking-thrush, and a second island some other quite dis- 

 tinct genus; if one island had its genus of lizard, and a 

 second island another distinct genus, or none whatever; or 

 if the different islands were inhabited, not by representative 

 species of the same genera of plants, but by totally different 

 genera, as does to a certain extent hold good: for, to give 

 one instance, a large berry-bearing tree at James Island has 

 no representative species in Charles Island. [JBut it is the 

 circumstance, that several of the islands possess their own 

 species of the tortoise, mocking-thrush, finches, and numer- 

 ous plants, these species having the same general habits, 

 occupying analogous situations, and obviously filling the 

 same place in the natural economy of this archipelago, that 

 strikes me with wonder.^JTt may be suspected that some of 

 these representative species, at least in the case of the tor- 

 toise and of some of the birds, may hereafter prove to be 

 only well-marked races ; but this would be of equally great 

 interest to the philosophical naturalist. I have said that most 

 of the islands are in sight of each other: I may specify that 

 Charles Island is fifty miles from the nearest part of Chat- 

 ham Island, and thirty-three miles from the nearest part of 



