1875. | THE GALAPAGOS ARCHIPELAGO. 271 
was then formed; and from the account given of it by Mr. Gould in 
the Zoological Society’s ‘ Proceedings,’ and by Mr. Darwin in ‘ The 
Zoology of the voyage of the ‘ Beagle,’ we have the first introduction 
to the Birds of the archipelago. Two other considerable collections 
have been subsequently made—one by the officers of the Swedish 
frigate ‘ Eugenies,’ and the other by Dr. Habel. A few specimens 
were also obtained during the voyage of the French ship ‘ Vénus,’ as 
well as a few by Capt. Kellett and Lieut. Wood in the ‘ Herald’ and 
‘Pandora.’ I also suppose that Prof. Agassiz, during the ‘ Hassler’ 
expedition, collected birds on these islands; but of them, if they 
exist, no account has ever yet been published. 
Fifty-six species of Birds have been recorded as inhabitants of the 
Galapagos archipelago: of these about two thirds are peculiar to the 
group ; the remainder are species of wide range and belong chiefly to 
families of Sea-Birds and Waders. 
The affinity of the Birds of the islands lies entirely with those of 
the adjoining continent of South America, whether viewed as regards 
families, genera, or species. 
The distribution of the Birds in the different islands still requires 
investigation. Few species, however, are restricted in their range to 
one island; and further research will, I think, tend to show that, so 
far as the Birds are concerned, hardly any indigenous bird will be 
found ultimately to inhabit one island alone. 
One singular feature is especially worthy of notice with respect to 
the genus of Finches (Geospiza) which frequents the islands. I re- 
fer to the remarkable variation observable in the size of these birds, 
especially as regards their bills. Mr. Darwin was much struck with 
this circumstance. Individual birds vary to such an extent that I 
fully believe that a gradual series could be gathered to show that these 
birds’ beaks vary from the size of that of a Hawfinch (Coccothraustes) 
to that of a Bunting (Eméberiza). 
Several species have been characterized from the different sizes of 
bills of these birds ; but were the difference once shown to be capable 
of being destroyed by the interposition of intermediate specimens, our 
usual means of defining species would fail, and the result would compel 
us to unite all under one specific denomination. As Dr. Habel’s notes, 
however, rather tend than otherwise to show that individuals group 
themselves to some extent with regard to their size, I have thought 
it best to adhere for the present to the plan adopted by Mr. Gould, 
and endeavour to differentiate the species described by him. In doing 
so, however, I feel that I have assigned rather arbitrary specific cha- 
racters, based on size alone, to some of the so-called species. 
Under favourable circumstances for the maintenance of these birds, 
coupled with a tendency to vary considerably as regards size, natural 
selection seems to have acted with great laxity in eliminating inter- 
mediate forms. 
Lastly, I have drawn up a few suggestions to guide future 
explorers, and have endeavoured to point out as to which islands our 
knowledge of the avifauna is incomplete or totally wanting. The 
large island of Albemarle remains practically unexplored. Nothing 
