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 EricinidcB 

 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 all 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. 



(3 16.) 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 



