280 Proceedings of the Royal Society 
improved bill and wing would naturally tend to be perpetuated by 
ordinary generation. This is unquestionably true ; but it really does 
not touch the facts of the case. The bills and wings of the different 
genera do not differ from each other in respect of any comparative 
advantage of this kind, but simply in respect to variety correspond- 
ing with the variety of certain vegetable forms. One form of bill is 
as good as another, but some forms are adapted to some special 
class of flower. Some bills, for example, are formed of enormous 
length, specially adapted to obtain access to the nectar chambers of 
long tubular flowers, such as the Brugmansia. Some, on the other 
hand, as if to show that the same end may be attained by 
diff'erent means, obtain access to the same flowers by a shorter pro- 
cess, and pierce the bases of the corolla instead of seeking access by 
the mouth. Some have bills bent downwards like a sickle, adapted 
to searching the bark of palm-trees for the insects hid under the 
scaly covering; others have bills curved in the opposite direction, 
fitted, apparently, to the curious construction of some of the great 
family of Orchids so immensely developed in the forests of Central 
America. Some have bills equally well adapted for searching a 
vast variety of flowers and blossoms, and these, accordingly, 
migrate with the flowering season, and issuing from the great 
stronghold of the family in tropical America, spread like our own 
summer birds of passage, northwards to Canada, and southwards to 
Cape Horn, in the corresponding seasons of the year. In contrast 
with these species of extended range, there are many species whose 
habitat is confined, perhaps, to a single mountain, and there are 
some which never have been seen beyond the edges of some extinct 
volcano, whose crater is now filled with a special flora. Many of 
the great mountains of the Andes have each of them species 
peculiar to themselves. On Chimborazo and Cotopaxi, and other 
summits, special forms of Humming-birds are found in special 
zones of vegetation even close up to the limits of perpetual snow. 
Again, many of the islands have species peculiar to themselves. 
The little island of Juan Fernandez, 300 miles from the main- 
land, has three species peculiar to itself, of which two are so distinct 
from all others known, that they cannot for a moment be con- 
founded with any of them. It is impossible not to see, in such com- 
plicated facts as these, that the creation of new species has followed 
