380 GALAPAGOS ARCHIPELAGO. [chap. xvii. 



group), even to that of a warbler. The largest beak in the genus 

 Geospiza is shown in Fig. 1, and the smallest in Fig. 3; but 

 instead of there being' only one intermediate species, with a beak 

 of the size shown in Fig-. 2, there are no less than six species 

 with insensibly graduated beaks. The beak of the sub-group 

 Certhidea, is shown in Fig. 4. The beak of Cactornis is some- 

 what like that of a starling; and that of the fourth sub-group, 

 Camarhynchus, is slightly parrot-shaped. Seeing this gradation 

 and diversity of structure in one small, intimately related group 

 of birds, one might really fancy that from an original paucity of 

 birds in this archipelago, one species had been taken and modi- 

 fied for different ends. In a like manner it might be fancied that a 

 bird originally a buzzard, had been induced here to undertake the 

 office of the carrion-feeding Polybori of the American continent. 



Of waders and water-birds I was able to get only eleven kinds, 

 and of these only three (including a rail confined to the damp sum- 

 mits of the islands) are new species. Considering the wandering 

 habits of the gulls, I was surprised to find that the species in- 

 habiting these islands is peculiar, but allied to one from the 

 southern parts of South America. The far greater peculiarity of 

 the land-birds, namely, twenty-five out of twenty-six being new 

 species or at least new races, compared with the waders and 

 web-footed birds, is in accordance with the greater range which 

 these latter orders have in all parts of the world. A\^e shall 

 hereafter see this law of aquatic forms, whether marine or 

 fresh-water, being less peculiar at any given point of the earth's 

 surface than the terrestrial forms of the same classes, strikingly 

 illustrated in the shells, and in a lesser degree in the insects of 

 this archipelago. 



Two of the waders are rather smaller than the same species 

 brought from other places : the swallow is also smaller, though 

 it is doubtful whether or not it is distinct from its analogue. 

 The two owls, the two tyrant fly-catchers (Pyrocephalus) and the 

 dove, are also smaller than the analogous but distinct species, to 

 which they are most nearly related ; on the other hand, the gull 

 is rather larger. The two owls, the swallow, all three species of 

 mocking-thrushj the dove in its separate colours though not in its 

 whole plumage, the Totanus, and the gull, are likewise duskier co- 

 loured than their analogous species ; and in the case of the mock 



