XVII 
BIRDS 
405 
most curious fact is the perfect gradation in the size of the 
beaks in the different species of Geospiza, from one as large as 
that of a hawfinch to that of a chaffipch, and (if Mr. Gould is 
right in including his sub-group, Certhidea, in the main 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 
1 2 
1. Geospiza magnirostris. 2. Geospiza fortis. 
3. Geospiza parvula. 4. Certhidea olivacea. 
FINCHES FROM GALAPAGOS ARCHIPELAGO. 
Cactornis is somewhat 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 modified 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 summits of the islands) are new species. Considering 
