252 FIRST PRINCIPLES OF NATURAL CLASSIFICATION. 



in any group which joined,, and immediately blended into, 

 the sub-typical (304.). We have seen that the feet 

 are slightly, and often not at all, developed : an incapacity 

 for quick motion is the natural result of such an organ- 

 isation ; and hence it might theoretically he concluded 

 that the feet are never used in the pursuit or capture of 

 their prey. Now this is truly the case in numerous 

 instances : natatorial types seize their food by the mouth 

 alone ; and all such as do not swim, or pursue their 

 prey by their wings, dart upon it from a fixed station, 

 as if incapacitated to rove about in its search, like other 

 animals, by the imperfection of their feet : the king- 

 fishers, the herons, flycatchers, and innumerable other 

 groups, are all well known instances of this habit, not to 

 mention the whole tribe of Fissirostres among perching 

 birds. The Cirripedes, or barnacles (the natatorial type 

 of the Annulosa), and all others whose body is fixed, 

 show us the same principle developed under a different 

 aspect ; for here the habits of the animal at all times are 

 so sedentary, that they seem absolutely incapable of 

 moving from the spot where they complete their last or 

 final change of form. The Hesperian butterflies (Hes- 

 peridfe) are the most sedentary, in their larva state, of 

 all true insects, for they fabricate and live in a little cell, 

 formed by a leaf rolled into a cylinder. Every natural 

 group, in short, contains some one representation of this 

 type : we have not yet determined, however, whether all 

 internal feeders are of the natatorial (or apod) type. 



(312.) Let us now look for verifications of the fore- 

 going theory among some of the best known animals ; 

 all of which, in their own respective circles, belong to 

 this type of form. First we have the whales, the 

 leviathans of creation, before whose stupendous size 

 even the elephant shrinks into moderate dimensions: 

 the head is nearly as large as the whole body, the 

 mouth is of vast size, and although a quadruped, it is 

 apodal, or without feet. It lives in the waters, and the 

 snout is so obtuse and blunt, that the extremity appears 

 as if cut off. Next to these gigantic animals the hippo- 



