SYSTEM OF NATURE. 
49 
domestic poultry — the storks and cranes, plovers, bus¬ 
tards, ostriches, &c. — are the Belluae among birds : these 
are walking birds. Nearly all ornithological writers agree 
in separating the gallinaceous from the wading birds : the 
following question arises on the propriety of this arrange¬ 
ment— If the Gallinae and Grallae are natural and equiva¬ 
lent groups, in which must we place the ostrich and the 
pigeon ? In a group so comprehensive as to include all 
the walkers, we can admit the ostrich, the cassowary, the 
apteryx, the bustard and the pigeons; but if we restrict 
our groups to the Gallinae and Grallae, then the ostrich &c. 
must constitute a third group, and the pigeons a fourth, 
and when this is done the hopping birds must be equally 
subdivided, or the divisions will still want uniformity. 
7thly. The Natatores, or rather the web-footed placentals. 
Are not these closely represented by the web-footed birds ? 
In some — as in the penguin — the wings have ceased to 
perform the office of flight, and are used like the paddles 
of a turtle or manatus as implements of swimming. The 
penguin and its congeners, therefore, are the Cete among 
birds. They are preeminently swimming birds. It is in¬ 
teresting to observe that, in groups united by such a com¬ 
prehensive character as that of swimming, there is precisely 
that variety of general character which so great a latitude 
would lead us to anticipate. The entire economy of the 
animal is changed: its habitat is water instead of land ; 
but as the water furnishes for both, every variety of organ¬ 
ized life for food, we are led to suppose that each kind 
would be sought as much by aquatic as by terrestrial ani¬ 
mals. We have already seen this observation verified in 
the swimming placentals, and on investigation we shall find 
it equally observable in the swimming birds. The gulls are 
E 
