8 
SYSTEM OF NATURE. 
and signally distinct. In one of these groups — the pla¬ 
cental animals — we find a bat, an ant-eater, and a dol¬ 
phin, and these respectively structurally resemble a bird, 
a reptile, and a fish. It appears to me that this structural 
resemblance can only be shown by placing the placental 
animals in the centre, and the others around them. 
From this principle of approximating like to like certain 
seemingly cabalistic numbers or figures may perchance 
result, but a long and careful consideration of this branch 
of the enquiry has thoroughly convinced me that such 
numbers and figures are the result of a principle, and not 
the principle itself. But another result is deducible from 
this besides the position of the three exterior groups. 
Bats, ant-eaters and dolphins, though truly placental, vi¬ 
viparous and mammalious animals, are extreme or abnor¬ 
mal forms : the normal forms—those animals emphatically 
called quadrupeds—must be placed within these ; and so 
we are induced to adopt a belief in the existence of nor¬ 
mal superior centres throughout the animal kingdom. I 
am willing to confess the difficulty there is in finding these 
normal centres, and the great uncertainty which must pre¬ 
vail as to what characters shall intimate such normal and 
central superiority; nor in my fondest anticipations for 
the reception of this system, do I ever picture to myself 
the pleasure of seeing the point definitively settled in more 
than a very few instances. 
In looking for a centre around which to arrange the al¬ 
most infinite hosts of the animal kingdom, vanity may 
perhaps induce man to select himself; yet, whatever the 
motive in making it, this choice is apparently sanctioned 
by reason and research, for all the observations of our 
comparative anatomists tend to show the propriety as well 
