2S8 



GALAPAGOS ARCHIPELAGO. 



[CHAP. xvn. 



marked races or varieties ; but the Mimus trifasciatus is very distinct. 

 Unfortunately most of the specimens of the finch tribe were mingled 

 together ; but I have strong reasons to suspect that some of the species 

 of the sub-group Geospiza are confined to separate islands. If the 

 different islands have their representatives of Geospiza, it may help to 

 explain the singularly large number of the species of this sub-group in 

 this one small archipelago, and as a probable consequence of their 

 numbers, the perfectly graduated series in the size of their beaks. 

 Two species of the sub-group Cactornis, and two of Camarhynchus, 

 were procured in the archipelago ; and of the numerous specimens of 

 these two sub-groups shot by four collectors at James Island, all were 

 found to belong to one species of each ; whereas the numerous speci- 

 mens shot either on Chatham or Charles Island (for the two sets were 

 mingled together) all belonged to the two other species ; hence we may 

 feel almost sure that these islands possess their representative species 

 of these two sub-groups. In land-shells this law of distribution does 

 not appear to hold good. In my very small collection of insects, Mr. 

 Waterhcuse remarks, that of those which were ticketed with their 

 locality, not one was common to any two of the islands. 



If we now turn to the Flora, we shall find the aboriginal plants oi 

 the different islands wonderfully different. I give all the following 

 results on the high authority of my friend Dr. J. Hooker. I may 

 premise that I indiscriminately collected everything in flower on the 

 different islands, and fortunately kept my collections separate. Too 

 much confidence, however, must not be placed in the proportional 

 results, as the small collections brought home by some other naturalists, 

 though in some respects confirming the results, plainly show that much 

 remains to be done in the botany of this group ; the Leguminosae, 

 moreover, have as yet been only approximately worked out : 



Hence we have the truly wonderful fact, that in James Island, of the 

 thirty-eight Galapageian plants, or those found in no other part of the 

 world, thirty are exclusively confined to this one island; and in 



