RESULTS OF NUMERICAL EQUALITY IN TRIBES. 233 
arace. If, then, all the fossil Pachydermata were 
alive, and were incorporated, according to their 
affinities, with those now living, the contents of the 
whole group would probably be augmented to four 
or five times its present number; and those chasms, 
which now appear so wide, would be proportionably 
lessened ; nay, it is highly probable they would not 
be greater, in proportion, than those between the 
different genera of the parrots. But, secondly, let 
us suppose that it was essential to the symmetry 
and harmony of nature, that all her groups of the 
same rank and value should contain pretty nearly 
the same number of species, and that their numerical 
contents should be proportionate to their value. 
What, in the present instance, would be the result ? 
The tribe of Scansores, or climbing birds, includes 
the parrots; and, upon a rough estimate, certainly 
contains between four and five hundred species. 
We know, by induction, that this tribe is equivalent 
to that of the pachydermatous quadrupeds. Now, 
if these tribes were as equal in their contents, as they 
are in their rank, more than half the earth would be 
overrun with monsters. Elephants would be as 
common as flies; we should have to reckon not two, 
but perhaps two hundred species. All the large 
rivers would be almost choked with hippopotami. 
Rhinoceroses would swarm in the woods, in herds 
of thousands, as the parrots do now in the forests of 
America. And huge megatheri, perhaps of a hun- 
dred species, would attack a forest, and strip it of 
its verdure in a few days. The world, in fact, 
would be filled, as it once was, with monstrous 
animals; and man would find no resting place in it, 
