380 GALAPAGOS ARCHIPELAGO. [cuar. xvin 
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. Ina like manner it might be fancied thata 
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. We 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-thrush, 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- 
