6 
ON THE CLASSIFICATION OF BIRDS. 
distinctions of their class. They are birds which can- 
not flyj and which have no real feathers. They walk, 
indeed, upon two feet ; but so does the kangaroo and the 
jerboa, which, indeed, are quadrupeds, but whose fore 
feet are as little developed as the wings of the ostrich. 
True it is, that we can have no hesitation in referring 
each of these animals to their proper class ; and, there- 
fore, it may be said, there are still gaps in the chain. 
We freely admit this. But the question is, not whether 
the series of links are perfect, but whether the last in 
each does not liear all the marks of having been for- 
merly united by means of some few wliich are lost. 
If the Ornithnrhynchus, of aU existing quadrupeds, 
evinces the nearest approach to birds, and the ostrich, 
among birds, shows the like tendency towards the struc- 
ture of quadrupeds, we have all the evidence requisite 
to prove their relationship. 
(6.) We have said that birds are the butterflies of 
the vertebrated animals, not merely in the figurative 
imagery of poetry, but in the sober language of science. 
This analogy will be at once apparent, on comparing the 
circle of the animal kingdom with that of the vertebrated 
animals. 
Circle of the 
V ^rtebrata. 
AnS,fiamdL. Characters. 
Typical Characters. 
Notwithstanding what has been said (1.) on the many 
circumstances which give to birds a greater interest than 
we in general feel towards quadrupeds, it must be re- 
membered that these latter are a much more highly 
organised class, and that therefore they exhibit the per. 
fection, or types, not only of the vertebrated circle, but 
of the entire animal kingdom. Annulose animals, or 
insects, are the next in rank ; and the most perfect of 
these are the Pti/ote, or winged class, at the head of which 
stands the order Lejiidoptem. Hence, one of the most 
