256 FIRST PRINCIPLES OF NATURAL CLASSIFICATION. 
idea of the suctorial structure. That well-known animal, 
the common medicinal leech, represents the suctorial 
Vermes in the circle of the Annelides, or red-blooded 
worms, and brings before us some of the most striking 
properties of this type. As we proceed to trace these 
characters in the groups of more perfectly constructed 
animals, we find in the tortoises the faintest develope- 
ment of the vertebrated structure ; while the singular 
defence with which nature has provided them, is again 
produced in the more immediate groups of Dasypus and 
Manis (the armadillo and scaly ant-eaters) among 
quadrupeds, in the remoter instances of the Coleoptera 
among the Ptilota, and the larva of the Ericinide 
among the Lepidoptera. The singular resemblance 
which the chelonian fishes, forming the order Branchio- 
steges, bear to the tortoises and turtles, must strike every 
one ; and it is worthy of notice, that throughout these 
groups the mouth is particularly small, and in very 
many instances entirely destitute of teeth. The suc- 
torial types among the quadrupeds contain ail those 
which have the jaws or muzzle produced to an ex- 
traordinary length ; witness the moles, the ant-eaters, 
the armadillos, the pigs, and the whole family of mice. 
Now, this is precisely the structure of all the types of 
the suctorial birds: for the Grallatores, or waders, have 
the longest bills and the smallest mouths of any in the 
whole class ; while the humming-birds (by which the 
waders are represented in the great order of Insessores) 
live entirely by suction, and are remarkable both for 
the great length and slenderness of their bill, and the 
extreme narrowness of their gape. 
(316.) In regard to the motion of suctorial types, 
we have said that they exhibit amazing powers of leap- 
ing ; but this does not appear to be a character of such 
universality as many of those we have noticed. The 
flea is, nevertheless, a well known and familiar example 
among insects, as the jerboa and the kangaroo in the 
circle of quadrupeds ; while the wading birds, although 
not saltatorial, are the swiftest runners of the feathered 
